From 01b2352628fa5c8251a4db4f05a00d62a3eab439 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 13:49:40 -0700
Subject: [PATCH 01/16] Speed up interpreter detection

---
 .../services/cacheableLocatorService.ts       |  2 +
 .../workspaceVirtualEnvWatcherService.ts      | 51 ++++++++++++++-----
 ...spaceVirtualEnvWatcherService.unit.test.ts |  7 ++-
 3 files changed, 44 insertions(+), 16 deletions(-)

diff --git a/src/client/interpreter/locators/services/cacheableLocatorService.ts b/src/client/interpreter/locators/services/cacheableLocatorService.ts
index ca5a35ddd387..ecac28ee6d33 100644
--- a/src/client/interpreter/locators/services/cacheableLocatorService.ts
+++ b/src/client/interpreter/locators/services/cacheableLocatorService.ts
@@ -7,6 +7,7 @@ import { injectable, unmanaged } from 'inversify';
 import * as md5 from 'md5';
 import { Disposable, Uri } from 'vscode';
 import { IWorkspaceService } from '../../../common/application/types';
+import '../../../common/extensions';
 import { Logger } from '../../../common/logger';
 import { IDisposableRegistry, IPersistentStateFactory } from '../../../common/types';
 import { createDeferred, Deferred } from '../../../common/utils/async';
@@ -60,6 +61,7 @@ export abstract class CacheableLocatorService implements IInterpreterLocatorServ
             watcher.onDidCreate(() => {
                 Logger.verbose(`Interpreter Watcher change handler for ${this.cacheKeyPrefix}`);
                 this.promisesPerResource.delete(cacheKey);
+                this.getInterpreters(resource).ignoreErrors();
             }, this, disposableRegisry);
         });
     }
diff --git a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
index 7217150d392a..75181f901158 100644
--- a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
+++ b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
@@ -9,18 +9,23 @@ import { Disposable, Event, EventEmitter, FileSystemWatcher, RelativePattern, Ur
 import { IWorkspaceService } from '../../../common/application/types';
 import { Logger, traceVerbose } from '../../../common/logger';
 import { IPlatformService } from '../../../common/platform/types';
+import { IPythonExecutionFactory } from '../../../common/process/types';
 import { IDisposableRegistry } from '../../../common/types';
 import { debounce } from '../../../common/utils/decorators';
 import { IInterpreterWatcher } from '../../contracts';
 
+const maxTimeToWaitForEnvCreation = 60_000;
+const timeToPollForEnvCreation = 5_000;
+
 @injectable()
 export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, Disposable {
-    private readonly didCreate;
-    private timer?: NodeJS.Timer;
+    private readonly didCreate: EventEmitter<void>;
+    private timers = new Map<string, { timer: NodeJS.Timer; counter: number }>();
     private fsWatchers: FileSystemWatcher[] = [];
     constructor(@inject(IDisposableRegistry) private readonly disposableRegistry: Disposable[],
         @inject(IWorkspaceService) private readonly workspaceService: IWorkspaceService,
-        @inject(IPlatformService) private readonly platformService: IPlatformService) {
+        @inject(IPlatformService) private readonly platformService: IPlatformService,
+        @inject(IPythonExecutionFactory) private readonly pythonExecFactory: IPythonExecutionFactory) {
         this.didCreate = new EventEmitter<void>();
         disposableRegistry.push(this);
     }
@@ -28,7 +33,7 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
         return this.didCreate.event;
     }
     public dispose() {
-        this.clearTimer();
+        this.clearTimers();
     }
     @traceVerbose('Register Intepreter Watcher')
     public async register(resource: Uri | undefined): Promise<void> {
@@ -55,18 +60,36 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
     @traceVerbose('Intepreter Watcher change handler')
     protected createHandler(e: Uri) {
         this.didCreate.fire();
-        // On Windows, creation of environments are slow, hence lets notify again after 10 seconds.
-        this.clearTimer();
 
-        this.timer = setTimeout(() => {
-            this.timer = undefined;
-            this.didCreate.fire();
-        }, 10000);
+        // On Windows, creation of environments are very slow, hence lets notify again after
+        // the python executable is accessible (i.e. when we can launch the process).
+        this.notifyCreationWhenReady(e.fsPath).ignoreErrors();
     }
-    private clearTimer() {
-        if (this.timer) {
-            clearTimeout(this.timer);
-            this.timer = undefined;
+    protected async notifyCreationWhenReady(pythonPath: string) {
+        const isValid = await this.isValidExecutable(pythonPath);
+        if (isValid) {
+            this.timers.delete(pythonPath);
+            return this.didCreate.fire();
+        }
+        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
+        if (counter > (maxTimeToWaitForEnvCreation / timeToPollForEnvCreation)) {
+            this.timers.delete(pythonPath);
+            return;
         }
+
+        const timer = setTimeout(() => {
+            this.didCreate.fire();
+            this.notifyCreationWhenReady(pythonPath).ignoreErrors();
+        }, timeToPollForEnvCreation);
+        this.timers.set(pythonPath, { timer, counter });
+    }
+    private clearTimers() {
+        this.timers.forEach(item => clearTimeout(item.timer));
+        this.timers.clear();
+    }
+    private async isValidExecutable(pythonPath: string): Promise<boolean> {
+        const execService = await this.pythonExecFactory.create({ pythonPath });
+        const info = await execService.getInterpreterInformation().catch(() => undefined);
+        return info !== undefined;
     }
 }
diff --git a/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts b/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
index ccb7e5ded248..026704ad4415 100644
--- a/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
+++ b/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
@@ -12,6 +12,7 @@ import { Disposable, FileSystemWatcher, Uri, WorkspaceFolder } from 'vscode';
 import { WorkspaceService } from '../../../client/common/application/workspace';
 import { isUnitTestExecution } from '../../../client/common/constants';
 import { PlatformService } from '../../../client/common/platform/platformService';
+import { PythonExecutionFactory } from '../../../client/common/process/pythonExecutionFactory';
 import { sleep } from '../../../client/common/utils/async';
 import { noop } from '../../../client/common/utils/misc';
 import { OSType } from '../../../client/common/utils/platform';
@@ -36,7 +37,8 @@ suite('Interpreters - Workspace VirtualEnv Watcher Service', () => {
     async function checkForFileChanges(os: OSType, resource: Uri | undefined, hasWorkspaceFolder: boolean) {
         const workspaceService = mock(WorkspaceService);
         const platformService = mock(PlatformService);
-        const watcher = new WorkspaceVirtualEnvWatcherService([], instance(workspaceService), instance(platformService));
+        const execFactory = mock(PythonExecutionFactory);
+        const watcher = new WorkspaceVirtualEnvWatcherService([], instance(workspaceService), instance(platformService), instance(execFactory));
 
         when(platformService.isWindows).thenReturn(os === OSType.Windows);
         when(platformService.isLinux).thenReturn(os === OSType.Linux);
@@ -80,7 +82,8 @@ suite('Interpreters - Workspace VirtualEnv Watcher Service', () => {
     async function ensureFileChanesAreHandled(os: OSType) {
         const workspaceService = mock(WorkspaceService);
         const platformService = mock(PlatformService);
-        const watcher = new WorkspaceVirtualEnvWatcherService(disposables, instance(workspaceService), instance(platformService));
+        const execFactory = mock(PythonExecutionFactory);
+        const watcher = new WorkspaceVirtualEnvWatcherService(disposables, instance(workspaceService), instance(platformService), instance(execFactory));
 
         when(platformService.isWindows).thenReturn(os === OSType.Windows);
         when(platformService.isLinux).thenReturn(os === OSType.Linux);

From b598a12630dec61d9510e5ca96f1e47a8f1c0858 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 14:20:00 -0700
Subject: [PATCH 02/16] Use separate urls for querying and downloading

---
 .../languageServer/languageServerPackageRepository.ts    | 9 +++++----
 src/client/common/nuget/azureBlobStoreNugetRepository.ts | 9 +++++----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/client/activation/languageServer/languageServerPackageRepository.ts b/src/client/activation/languageServer/languageServerPackageRepository.ts
index 710cc5d07a88..a4f38f1ed085 100644
--- a/src/client/activation/languageServer/languageServerPackageRepository.ts
+++ b/src/client/activation/languageServer/languageServerPackageRepository.ts
@@ -7,7 +7,8 @@ import { inject, injectable } from 'inversify';
 import { AzureBlobStoreNugetRepository } from '../../common/nuget/azureBlobStoreNugetRepository';
 import { IServiceContainer } from '../../ioc/types';
 
-const azureBlobStorageAccount = 'https://pvsc.azureedge.net';
+const azureBlobStorageAccount = 'https://pvsc.blob.core.windows.net';
+const azureCDNBlobStorageAccount = 'https://pvsc.azureedge.net';
 
 export enum LanguageServerDownloadChannel {
     stable = 'stable',
@@ -24,20 +25,20 @@ export enum LanguageServerPackageStorageContainers {
 @injectable()
 export class StableLanguageServerPackageRepository extends AzureBlobStoreNugetRepository {
     constructor(@inject(IServiceContainer) serviceContainer: IServiceContainer) {
-        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.stable);
+        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.stable, azureCDNBlobStorageAccount);
     }
 }
 
 @injectable()
 export class BetaLanguageServerPackageRepository extends AzureBlobStoreNugetRepository {
     constructor(@inject(IServiceContainer) serviceContainer: IServiceContainer) {
-        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.beta);
+        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.beta, azureCDNBlobStorageAccount);
     }
 }
 
 @injectable()
 export class DailyLanguageServerPackageRepository extends AzureBlobStoreNugetRepository {
     constructor(@inject(IServiceContainer) serviceContainer: IServiceContainer) {
-        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.daily);
+        super(serviceContainer, azureBlobStorageAccount, LanguageServerPackageStorageContainers.daily, azureCDNBlobStorageAccount);
     }
 }
diff --git a/src/client/common/nuget/azureBlobStoreNugetRepository.ts b/src/client/common/nuget/azureBlobStoreNugetRepository.ts
index 89e9a408079f..f3f995a4d7d3 100644
--- a/src/client/common/nuget/azureBlobStoreNugetRepository.ts
+++ b/src/client/common/nuget/azureBlobStoreNugetRepository.ts
@@ -15,14 +15,15 @@ import { INugetRepository, INugetService, NugetPackage } from './types';
 export class AzureBlobStoreNugetRepository implements INugetRepository {
     constructor(@inject(IServiceContainer) private readonly serviceContainer: IServiceContainer,
         @unmanaged() protected readonly azureBlobStorageAccount: string,
-        @unmanaged() protected readonly azureBlobStorageContainer: string) { }
+        @unmanaged() protected readonly azureBlobStorageContainer: string,
+        @unmanaged() protected readonly azureCDNBlobStorageAccount: string) { }
     public async getPackages(packageName: string): Promise<NugetPackage[]> {
-        return this.listPackages(this.azureBlobStorageAccount, this.azureBlobStorageContainer, packageName);
+        return this.listPackages(this.azureBlobStorageAccount, this.azureBlobStorageContainer, packageName, this.azureCDNBlobStorageAccount);
     }
 
     @captureTelemetry(PYTHON_LANGUAGE_SERVER_LIST_BLOB_STORE_PACKAGES)
     @traceVerbose('Listing Nuget Packages')
-    public listPackages(azureBlobStorageAccount: string, azureBlobStorageContainer: string, packageName: string) {
+    protected listPackages(azureBlobStorageAccount: string, azureBlobStorageContainer: string, packageName: string, azureCDNBlobStorageAccount: string) {
         // tslint:disable-next-line:no-require-imports
         const az = require('azure-storage') as typeof azStorageTypes;
         const blobStore = az.createBlobServiceAnonymous(azureBlobStorageAccount);
@@ -39,7 +40,7 @@ export class AzureBlobStoreNugetRepository implements INugetRepository {
                     resolve(result.entries.map(item => {
                         return {
                             package: item.name,
-                            uri: `${azureBlobStorageAccount}/${azureBlobStorageContainer}/${item.name}`,
+                            uri: `${azureCDNBlobStorageAccount}/${azureBlobStorageContainer}/${item.name}`,
                             version: nugetService.getVersionFromPackageFileName(item.name)
                         };
                     }));

From 9b940ef2e72b5fdb039f0b248d4db8dcbabe7ddc Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 14:29:07 -0700
Subject: [PATCH 03/16] Fix tests

---
 .../languageServer/languageServerPackageService.test.ts      | 5 ++++-
 src/test/common/nuget/azureBobStoreRepository.test.ts        | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/test/activation/languageServer/languageServerPackageService.test.ts b/src/test/activation/languageServer/languageServerPackageService.test.ts
index 677f03cfdadb..490e9c6e1bbb 100644
--- a/src/test/activation/languageServer/languageServerPackageService.test.ts
+++ b/src/test/activation/languageServer/languageServerPackageService.test.ts
@@ -21,6 +21,9 @@ import { PlatformService } from '../../../client/common/platform/platformService
 import { IPlatformService } from '../../../client/common/platform/types';
 import { IServiceContainer } from '../../../client/ioc/types';
 
+const azureBlobStorageAccount = 'https://pvsc.blob.core.windows.net';
+const azureCDNBlobStorageAccount = 'https://pvsc.azureedge.net';
+
 suite('Language Server Package Service', () => {
     let serviceContainer: typeMoq.IMock<IServiceContainer>;
     setup(() => {
@@ -76,7 +79,7 @@ suite('Language Server Package Service', () => {
         const platformService = new PlatformService();
         serviceContainer.setup(c => c.get(typeMoq.It.isValue(IPlatformService))).returns(() => platformService);
         const defaultStorageChannel = LanguageServerPackageStorageContainers.stable;
-        const nugetRepo = new AzureBlobStoreNugetRepository(serviceContainer.object, 'https://pvsc.azureedge.net', defaultStorageChannel);
+        const nugetRepo = new AzureBlobStoreNugetRepository(serviceContainer.object, azureBlobStorageAccount, defaultStorageChannel, azureCDNBlobStorageAccount);
         serviceContainer.setup(c => c.get(typeMoq.It.isValue(INugetRepository))).returns(() => nugetRepo);
         const lsPackageService = new LanguageServerPackageService(serviceContainer.object);
         const packageName = lsPackageService.getNugetPackageName();
diff --git a/src/test/common/nuget/azureBobStoreRepository.test.ts b/src/test/common/nuget/azureBobStoreRepository.test.ts
index dbc81768f77f..ab3224591493 100644
--- a/src/test/common/nuget/azureBobStoreRepository.test.ts
+++ b/src/test/common/nuget/azureBobStoreRepository.test.ts
@@ -15,6 +15,9 @@ import { PlatformService } from '../../../client/common/platform/platformService
 import { IPlatformService } from '../../../client/common/platform/types';
 import { IServiceContainer } from '../../../client/ioc/types';
 
+const azureBlobStorageAccount = 'https://pvsc.blob.core.windows.net';
+const azureCDNBlobStorageAccount = 'https://pvsc.azureedge.net';
+
 suite('Nuget Azure Storage Repository', () => {
     let serviceContainer: typeMoq.IMock<IServiceContainer>;
     let httpClient: typeMoq.IMock<IHttpClient>;
@@ -29,7 +32,7 @@ suite('Nuget Azure Storage Repository', () => {
         serviceContainer.setup(c => c.get(typeMoq.It.isValue(INugetService))).returns(() => nugetService.object);
         const defaultStorageChannel = LanguageServerPackageStorageContainers.stable;
 
-        repo = new AzureBlobStoreNugetRepository(serviceContainer.object, 'https://pvsc.azureedge.net', defaultStorageChannel);
+        repo = new AzureBlobStoreNugetRepository(serviceContainer.object, azureBlobStorageAccount, defaultStorageChannel, azureCDNBlobStorageAccount);
     });
 
     test('Get all packages', async function () {

From a1e248604ec0978cd2f9cbc64f0b3428846f61e6 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 14:51:51 -0700
Subject: [PATCH 04/16] Fix tests

---
 .../languageServer/languageServerPackageRepository.unit.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/activation/languageServer/languageServerPackageRepository.unit.test.ts b/src/test/activation/languageServer/languageServerPackageRepository.unit.test.ts
index 19bea10475da..6121dd59f46e 100644
--- a/src/test/activation/languageServer/languageServerPackageRepository.unit.test.ts
+++ b/src/test/activation/languageServer/languageServerPackageRepository.unit.test.ts
@@ -35,7 +35,7 @@ suite('Language Server Download Channels', () => {
         }
         const instance = new class extends classToCreate {
             constructor() { super(serviceContainer.object); }
-            public get storageAccount() { return this.azureBlobStorageAccount; }
+            public get storageAccount() { return this.azureCDNBlobStorageAccount; }
             public get storageContainer() { return this.azureBlobStorageContainer; }
         }();
 

From 332fead0306a47d16e6e15656bd869aa49ef1ef7 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 15:49:41 -0700
Subject: [PATCH 05/16] Fire notification immediately

---
 .../workspaceVirtualEnvWatcherService.ts      | 23 +++++++++----------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
index 75181f901158..8d099ebebc68 100644
--- a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
+++ b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
@@ -7,15 +7,15 @@ import { inject, injectable } from 'inversify';
 import * as path from 'path';
 import { Disposable, Event, EventEmitter, FileSystemWatcher, RelativePattern, Uri } from 'vscode';
 import { IWorkspaceService } from '../../../common/application/types';
+import '../../../common/extensions';
 import { Logger, traceVerbose } from '../../../common/logger';
 import { IPlatformService } from '../../../common/platform/types';
 import { IPythonExecutionFactory } from '../../../common/process/types';
 import { IDisposableRegistry } from '../../../common/types';
-import { debounce } from '../../../common/utils/decorators';
 import { IInterpreterWatcher } from '../../contracts';
 
 const maxTimeToWaitForEnvCreation = 60_000;
-const timeToPollForEnvCreation = 5_000;
+const timeToPollForEnvCreation = 2_000;
 
 @injectable()
 export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, Disposable {
@@ -56,31 +56,30 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
             this.fsWatchers.push(fsWatcher);
         }
     }
-    @debounce(2000)
     @traceVerbose('Intepreter Watcher change handler')
-    protected createHandler(e: Uri) {
+    protected async createHandler(e: Uri) {
         this.didCreate.fire();
-
         // On Windows, creation of environments are very slow, hence lets notify again after
         // the python executable is accessible (i.e. when we can launch the process).
         this.notifyCreationWhenReady(e.fsPath).ignoreErrors();
     }
     protected async notifyCreationWhenReady(pythonPath: string) {
+        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
         const isValid = await this.isValidExecutable(pythonPath);
         if (isValid) {
-            this.timers.delete(pythonPath);
-            return this.didCreate.fire();
+            if (counter > 0) {
+                this.didCreate.fire();
+            }
+            return this.timers.delete(pythonPath);
         }
-        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
         if (counter > (maxTimeToWaitForEnvCreation / timeToPollForEnvCreation)) {
+            // Send notification before we give up trying.
+            this.didCreate.fire();
             this.timers.delete(pythonPath);
             return;
         }
 
-        const timer = setTimeout(() => {
-            this.didCreate.fire();
-            this.notifyCreationWhenReady(pythonPath).ignoreErrors();
-        }, timeToPollForEnvCreation);
+        const timer = setTimeout(() => this.notifyCreationWhenReady(pythonPath).ignoreErrors(), timeToPollForEnvCreation);
         this.timers.set(pythonPath, { timer, counter });
     }
     private clearTimers() {

From 48e24e2d322bb78d6df441345d70e7e92d595fc4 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 13:49:40 -0700
Subject: [PATCH 06/16] Speed up interpreter detection

---
 .../services/cacheableLocatorService.ts       |  2 +
 .../workspaceVirtualEnvWatcherService.ts      | 51 ++++++++++++++-----
 ...spaceVirtualEnvWatcherService.unit.test.ts |  7 ++-
 3 files changed, 44 insertions(+), 16 deletions(-)

diff --git a/src/client/interpreter/locators/services/cacheableLocatorService.ts b/src/client/interpreter/locators/services/cacheableLocatorService.ts
index ca5a35ddd387..ecac28ee6d33 100644
--- a/src/client/interpreter/locators/services/cacheableLocatorService.ts
+++ b/src/client/interpreter/locators/services/cacheableLocatorService.ts
@@ -7,6 +7,7 @@ import { injectable, unmanaged } from 'inversify';
 import * as md5 from 'md5';
 import { Disposable, Uri } from 'vscode';
 import { IWorkspaceService } from '../../../common/application/types';
+import '../../../common/extensions';
 import { Logger } from '../../../common/logger';
 import { IDisposableRegistry, IPersistentStateFactory } from '../../../common/types';
 import { createDeferred, Deferred } from '../../../common/utils/async';
@@ -60,6 +61,7 @@ export abstract class CacheableLocatorService implements IInterpreterLocatorServ
             watcher.onDidCreate(() => {
                 Logger.verbose(`Interpreter Watcher change handler for ${this.cacheKeyPrefix}`);
                 this.promisesPerResource.delete(cacheKey);
+                this.getInterpreters(resource).ignoreErrors();
             }, this, disposableRegisry);
         });
     }
diff --git a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
index 7217150d392a..75181f901158 100644
--- a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
+++ b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
@@ -9,18 +9,23 @@ import { Disposable, Event, EventEmitter, FileSystemWatcher, RelativePattern, Ur
 import { IWorkspaceService } from '../../../common/application/types';
 import { Logger, traceVerbose } from '../../../common/logger';
 import { IPlatformService } from '../../../common/platform/types';
+import { IPythonExecutionFactory } from '../../../common/process/types';
 import { IDisposableRegistry } from '../../../common/types';
 import { debounce } from '../../../common/utils/decorators';
 import { IInterpreterWatcher } from '../../contracts';
 
+const maxTimeToWaitForEnvCreation = 60_000;
+const timeToPollForEnvCreation = 5_000;
+
 @injectable()
 export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, Disposable {
-    private readonly didCreate;
-    private timer?: NodeJS.Timer;
+    private readonly didCreate: EventEmitter<void>;
+    private timers = new Map<string, { timer: NodeJS.Timer; counter: number }>();
     private fsWatchers: FileSystemWatcher[] = [];
     constructor(@inject(IDisposableRegistry) private readonly disposableRegistry: Disposable[],
         @inject(IWorkspaceService) private readonly workspaceService: IWorkspaceService,
-        @inject(IPlatformService) private readonly platformService: IPlatformService) {
+        @inject(IPlatformService) private readonly platformService: IPlatformService,
+        @inject(IPythonExecutionFactory) private readonly pythonExecFactory: IPythonExecutionFactory) {
         this.didCreate = new EventEmitter<void>();
         disposableRegistry.push(this);
     }
@@ -28,7 +33,7 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
         return this.didCreate.event;
     }
     public dispose() {
-        this.clearTimer();
+        this.clearTimers();
     }
     @traceVerbose('Register Intepreter Watcher')
     public async register(resource: Uri | undefined): Promise<void> {
@@ -55,18 +60,36 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
     @traceVerbose('Intepreter Watcher change handler')
     protected createHandler(e: Uri) {
         this.didCreate.fire();
-        // On Windows, creation of environments are slow, hence lets notify again after 10 seconds.
-        this.clearTimer();
 
-        this.timer = setTimeout(() => {
-            this.timer = undefined;
-            this.didCreate.fire();
-        }, 10000);
+        // On Windows, creation of environments are very slow, hence lets notify again after
+        // the python executable is accessible (i.e. when we can launch the process).
+        this.notifyCreationWhenReady(e.fsPath).ignoreErrors();
     }
-    private clearTimer() {
-        if (this.timer) {
-            clearTimeout(this.timer);
-            this.timer = undefined;
+    protected async notifyCreationWhenReady(pythonPath: string) {
+        const isValid = await this.isValidExecutable(pythonPath);
+        if (isValid) {
+            this.timers.delete(pythonPath);
+            return this.didCreate.fire();
+        }
+        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
+        if (counter > (maxTimeToWaitForEnvCreation / timeToPollForEnvCreation)) {
+            this.timers.delete(pythonPath);
+            return;
         }
+
+        const timer = setTimeout(() => {
+            this.didCreate.fire();
+            this.notifyCreationWhenReady(pythonPath).ignoreErrors();
+        }, timeToPollForEnvCreation);
+        this.timers.set(pythonPath, { timer, counter });
+    }
+    private clearTimers() {
+        this.timers.forEach(item => clearTimeout(item.timer));
+        this.timers.clear();
+    }
+    private async isValidExecutable(pythonPath: string): Promise<boolean> {
+        const execService = await this.pythonExecFactory.create({ pythonPath });
+        const info = await execService.getInterpreterInformation().catch(() => undefined);
+        return info !== undefined;
     }
 }
diff --git a/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts b/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
index ccb7e5ded248..026704ad4415 100644
--- a/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
+++ b/src/test/interpreters/locators/workspaceVirtualEnvWatcherService.unit.test.ts
@@ -12,6 +12,7 @@ import { Disposable, FileSystemWatcher, Uri, WorkspaceFolder } from 'vscode';
 import { WorkspaceService } from '../../../client/common/application/workspace';
 import { isUnitTestExecution } from '../../../client/common/constants';
 import { PlatformService } from '../../../client/common/platform/platformService';
+import { PythonExecutionFactory } from '../../../client/common/process/pythonExecutionFactory';
 import { sleep } from '../../../client/common/utils/async';
 import { noop } from '../../../client/common/utils/misc';
 import { OSType } from '../../../client/common/utils/platform';
@@ -36,7 +37,8 @@ suite('Interpreters - Workspace VirtualEnv Watcher Service', () => {
     async function checkForFileChanges(os: OSType, resource: Uri | undefined, hasWorkspaceFolder: boolean) {
         const workspaceService = mock(WorkspaceService);
         const platformService = mock(PlatformService);
-        const watcher = new WorkspaceVirtualEnvWatcherService([], instance(workspaceService), instance(platformService));
+        const execFactory = mock(PythonExecutionFactory);
+        const watcher = new WorkspaceVirtualEnvWatcherService([], instance(workspaceService), instance(platformService), instance(execFactory));
 
         when(platformService.isWindows).thenReturn(os === OSType.Windows);
         when(platformService.isLinux).thenReturn(os === OSType.Linux);
@@ -80,7 +82,8 @@ suite('Interpreters - Workspace VirtualEnv Watcher Service', () => {
     async function ensureFileChanesAreHandled(os: OSType) {
         const workspaceService = mock(WorkspaceService);
         const platformService = mock(PlatformService);
-        const watcher = new WorkspaceVirtualEnvWatcherService(disposables, instance(workspaceService), instance(platformService));
+        const execFactory = mock(PythonExecutionFactory);
+        const watcher = new WorkspaceVirtualEnvWatcherService(disposables, instance(workspaceService), instance(platformService), instance(execFactory));
 
         when(platformService.isWindows).thenReturn(os === OSType.Windows);
         when(platformService.isLinux).thenReturn(os === OSType.Linux);

From 99640aad927b33e9b448bf284bf038d1a54d93a4 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 15:49:41 -0700
Subject: [PATCH 07/16] Fire notification immediately

---
 .../workspaceVirtualEnvWatcherService.ts      | 23 +++++++++----------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
index 75181f901158..8d099ebebc68 100644
--- a/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
+++ b/src/client/interpreter/locators/services/workspaceVirtualEnvWatcherService.ts
@@ -7,15 +7,15 @@ import { inject, injectable } from 'inversify';
 import * as path from 'path';
 import { Disposable, Event, EventEmitter, FileSystemWatcher, RelativePattern, Uri } from 'vscode';
 import { IWorkspaceService } from '../../../common/application/types';
+import '../../../common/extensions';
 import { Logger, traceVerbose } from '../../../common/logger';
 import { IPlatformService } from '../../../common/platform/types';
 import { IPythonExecutionFactory } from '../../../common/process/types';
 import { IDisposableRegistry } from '../../../common/types';
-import { debounce } from '../../../common/utils/decorators';
 import { IInterpreterWatcher } from '../../contracts';
 
 const maxTimeToWaitForEnvCreation = 60_000;
-const timeToPollForEnvCreation = 5_000;
+const timeToPollForEnvCreation = 2_000;
 
 @injectable()
 export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, Disposable {
@@ -56,31 +56,30 @@ export class WorkspaceVirtualEnvWatcherService implements IInterpreterWatcher, D
             this.fsWatchers.push(fsWatcher);
         }
     }
-    @debounce(2000)
     @traceVerbose('Intepreter Watcher change handler')
-    protected createHandler(e: Uri) {
+    protected async createHandler(e: Uri) {
         this.didCreate.fire();
-
         // On Windows, creation of environments are very slow, hence lets notify again after
         // the python executable is accessible (i.e. when we can launch the process).
         this.notifyCreationWhenReady(e.fsPath).ignoreErrors();
     }
     protected async notifyCreationWhenReady(pythonPath: string) {
+        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
         const isValid = await this.isValidExecutable(pythonPath);
         if (isValid) {
-            this.timers.delete(pythonPath);
-            return this.didCreate.fire();
+            if (counter > 0) {
+                this.didCreate.fire();
+            }
+            return this.timers.delete(pythonPath);
         }
-        const counter = this.timers.has(pythonPath) ? this.timers.get(pythonPath)!.counter + 1 : 0;
         if (counter > (maxTimeToWaitForEnvCreation / timeToPollForEnvCreation)) {
+            // Send notification before we give up trying.
+            this.didCreate.fire();
             this.timers.delete(pythonPath);
             return;
         }
 
-        const timer = setTimeout(() => {
-            this.didCreate.fire();
-            this.notifyCreationWhenReady(pythonPath).ignoreErrors();
-        }, timeToPollForEnvCreation);
+        const timer = setTimeout(() => this.notifyCreationWhenReady(pythonPath).ignoreErrors(), timeToPollForEnvCreation);
         this.timers.set(pythonPath, { timer, counter });
     }
     private clearTimers() {

From 97bce590c5b3d4f09149bc695928f3dfe2e09569 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Wed, 31 Oct 2018 16:24:47 -0700
Subject: [PATCH 08/16] Update label

---
 .../diagnostics/checks/invalidPythonPathInDebugger.ts           | 2 +-
 src/client/interpreter/display/index.ts                         | 2 +-
 src/test/interpreters/display.unit.test.ts                      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/client/application/diagnostics/checks/invalidPythonPathInDebugger.ts b/src/client/application/diagnostics/checks/invalidPythonPathInDebugger.ts
index 643ea97ed586..1e31ca4f6fcd 100644
--- a/src/client/application/diagnostics/checks/invalidPythonPathInDebugger.ts
+++ b/src/client/application/diagnostics/checks/invalidPythonPathInDebugger.ts
@@ -16,7 +16,7 @@ import { DiagnosticCodes } from '../constants';
 import { DiagnosticCommandPromptHandlerServiceId, MessageCommandPrompt } from '../promptHandler';
 import { DiagnosticScope, IDiagnostic, IDiagnosticHandlerService, IInvalidPythonPathInDebuggerService } from '../types';
 
-const InvalidPythonPathInDebuggerMessage = 'You need to select a Python interpreter before you start debugging.\n\nTip: click on "Select Python Environment" in the status bar.';
+const InvalidPythonPathInDebuggerMessage = 'You need to select a Python interpreter before you start debugging.\n\nTip: click on "Select Python Interpreter" in the status bar.';
 
 export class InvalidPythonPathInDebuggerDiagnostic extends BaseDiagnostic {
     constructor() {
diff --git a/src/client/interpreter/display/index.ts b/src/client/interpreter/display/index.ts
index bba7dc3bd39e..281ad604f940 100644
--- a/src/client/interpreter/display/index.ts
+++ b/src/client/interpreter/display/index.ts
@@ -47,7 +47,7 @@ export class InterpreterDisplay implements IInterpreterDisplay {
         } else {
             this.statusBar.tooltip = '';
             this.statusBar.color = 'yellow';
-            this.statusBar.text = '$(alert) Select Python Environment';
+            this.statusBar.text = '$(alert) Select Python Interpreter';
         }
         this.statusBar.show();
     }
diff --git a/src/test/interpreters/display.unit.test.ts b/src/test/interpreters/display.unit.test.ts
index e3ca5f4f1f8c..8b08756d7814 100644
--- a/src/test/interpreters/display.unit.test.ts
+++ b/src/test/interpreters/display.unit.test.ts
@@ -136,7 +136,7 @@ suite('Interpreters Display', () => {
         await interpreterDisplay.refresh(resource);
 
         statusBar.verify(s => s.color = TypeMoq.It.isValue('yellow'), TypeMoq.Times.once());
-        statusBar.verify(s => s.text = TypeMoq.It.isValue('$(alert) Select Python Environment'), TypeMoq.Times.once());
+        statusBar.verify(s => s.text = TypeMoq.It.isValue('$(alert) Select Python Interpreter'), TypeMoq.Times.once());
     });
     test('Ensure we try to identify the active workspace when a resource is not provided ', async () => {
         const workspaceFolder = Uri.file('x');

From 299909cba90b8f941f4d80d6103a692d31fb6829 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 09:38:23 -0700
Subject: [PATCH 09/16] Add progress display

---
 .../activation/interpreterDataService.ts      |  2 +-
 .../languageServerFolderService.ts            |  4 +-
 .../common/application/applicationShell.ts    |  6 +-
 src/client/common/application/types.ts        | 27 +++++++-
 src/client/common/editor.ts                   |  2 +-
 src/client/common/envFileParser.ts            |  8 ++-
 src/client/common/installer/channelManager.ts |  4 +-
 src/client/common/utils/async.ts              |  9 +++
 src/client/common/utils/localize.ts           |  4 ++
 .../extension/configProviders/baseProvider.ts |  2 +-
 src/client/extension.ts                       | 13 ++--
 src/client/interpreter/contracts.ts           | 15 ++++-
 .../interpreter/display/progressDisplay.ts    | 46 +++++++++++++
 src/client/interpreter/interpreterService.ts  |  3 +-
 src/client/interpreter/locators/index.ts      | 14 +++-
 .../interpreter/locators/progressService.ts   | 65 +++++++++++++++++++
 .../services/cacheableLocatorService.ts       |  8 ++-
 src/client/interpreter/serviceRegistry.ts     |  7 ++
 src/client/typeFormatters/dispatcher.ts       |  4 +-
 src/client/unittests/unittest/helper.ts       |  2 +-
 20 files changed, 218 insertions(+), 27 deletions(-)
 create mode 100644 src/client/interpreter/display/progressDisplay.ts
 create mode 100644 src/client/interpreter/locators/progressService.ts

diff --git a/src/client/activation/interpreterDataService.ts b/src/client/activation/interpreterDataService.ts
index daa595ebf383..1e082bb171d5 100644
--- a/src/client/activation/interpreterDataService.ts
+++ b/src/client/activation/interpreterDataService.ts
@@ -40,7 +40,7 @@ export class InterpreterDataService {
     }
 
     const cacheKey = `InterpreterData-${interpreterPath}`;
-    let interpreterData = this.context.globalState.get(cacheKey) as InterpreterData;
+    let interpreterData = this.context.globalState.get<InterpreterData>(cacheKey);
     let interpreterChanged = false;
     if (interpreterData) {
       // Check if interpreter executable changed
diff --git a/src/client/activation/languageServer/languageServerFolderService.ts b/src/client/activation/languageServer/languageServerFolderService.ts
index 20e88669462d..57be87a36c50 100644
--- a/src/client/activation/languageServer/languageServerFolderService.ts
+++ b/src/client/activation/languageServer/languageServerFolderService.ts
@@ -65,8 +65,8 @@ export class LanguageServerFolderService implements ILanguageServerFolderService
         if (dirs.length === 0) {
             return;
         }
-        const sortedDirs = dirs.sort((a, b) => a.version.compare(b.version));
-        return sortedDirs[sortedDirs.length - 1];
+        dirs.sort((a, b) => a.version.compare(b.version));
+        return dirs[dirs.length - 1];
     }
     public async getExistingLanguageServerDirectories(): Promise<FolderVersionPair[]> {
         const fs = this.serviceContainer.get<IFileSystem>(IFileSystem);
diff --git a/src/client/common/application/applicationShell.ts b/src/client/common/application/applicationShell.ts
index e956becd2204..a66e5c4e9594 100644
--- a/src/client/common/application/applicationShell.ts
+++ b/src/client/common/application/applicationShell.ts
@@ -6,7 +6,7 @@
 const opn = require('opn');
 
 import { injectable } from 'inversify';
-import { CancellationToken, Disposable, InputBoxOptions, MessageItem, MessageOptions, OpenDialogOptions, QuickPickItem, QuickPickOptions, SaveDialogOptions, StatusBarAlignment, StatusBarItem, Uri, window, WorkspaceFolder, WorkspaceFolderPickOptions } from 'vscode';
+import { CancellationToken, Disposable, InputBoxOptions, MessageItem, MessageOptions, OpenDialogOptions, Progress, ProgressOptions, QuickPickItem, QuickPickOptions, SaveDialogOptions, StatusBarAlignment, StatusBarItem, Uri, window, WorkspaceFolder, WorkspaceFolderPickOptions } from 'vscode';
 import { IApplicationShell } from './types';
 
 @injectable()
@@ -67,5 +67,7 @@ export class ApplicationShell implements IApplicationShell {
     public showWorkspaceFolderPick(options?: WorkspaceFolderPickOptions): Thenable<WorkspaceFolder | undefined> {
         return window.showWorkspaceFolderPick(options);
     }
-
+    public withProgress<R>(options: ProgressOptions, task: (progress: Progress<{ message?: string; increment?: number }>, token: CancellationToken) => Thenable<R>): Thenable<R> {
+        return window.withProgress<R>(options, task);
+    }
 }
diff --git a/src/client/common/application/types.ts b/src/client/common/application/types.ts
index 1e045842ed99..070c4a6e0f67 100644
--- a/src/client/common/application/types.ts
+++ b/src/client/common/application/types.ts
@@ -7,9 +7,9 @@
 import {
     Breakpoint, BreakpointsChangeEvent, CancellationToken, ConfigurationChangeEvent, DebugConfiguration, DebugConfigurationProvider, DebugConsole, DebugSession, DebugSessionCustomEvent, Disposable,
     Event, FileSystemWatcher, GlobPattern, InputBoxOptions, MessageItem,
-    MessageOptions, OpenDialogOptions, QuickPickItem, QuickPickOptions, SaveDialogOptions, StatusBarAlignment, StatusBarItem,
-    Terminal, TerminalOptions, TextDocument, TextDocumentShowOptions, TextEditor, TextEditorEdit, TextEditorOptionsChangeEvent, TextEditorSelectionChangeEvent,
-    TextEditorViewColumnChangeEvent, Uri, ViewColumn, WorkspaceConfiguration, WorkspaceEdit, WorkspaceFolder, WorkspaceFolderPickOptions, WorkspaceFoldersChangeEvent
+    MessageOptions, OpenDialogOptions, Progress, ProgressOptions, QuickPickItem, QuickPickOptions, SaveDialogOptions,
+    StatusBarAlignment, StatusBarItem, Terminal, TerminalOptions, TextDocument, TextDocumentShowOptions, TextEditor, TextEditorEdit,
+    TextEditorOptionsChangeEvent, TextEditorSelectionChangeEvent, TextEditorViewColumnChangeEvent, Uri, ViewColumn, WorkspaceConfiguration, WorkspaceEdit, WorkspaceFolder, WorkspaceFolderPickOptions, WorkspaceFoldersChangeEvent
 } from 'vscode';
 
 export const IApplicationShell = Symbol('IApplicationShell');
@@ -248,6 +248,27 @@ export interface IApplicationShell {
      * @return A promise that resolves to the workspace folder or `undefined`.
      */
     showWorkspaceFolderPick(options?: WorkspaceFolderPickOptions): Thenable<WorkspaceFolder | undefined>;
+
+    /**
+     * Show progress in the editor. Progress is shown while running the given callback
+     * and while the promise it returned isn't resolved nor rejected. The location at which
+     * progress should show (and other details) is defined via the passed [`ProgressOptions`](#ProgressOptions).
+     *
+     * @param task A callback returning a promise. Progress state can be reported with
+     * the provided [progress](#Progress)-object.
+     *
+     * To report discrete progress, use `increment` to indicate how much work has been completed. Each call with
+     * a `increment` value will be summed up and reflected as overall progress until 100% is reached (a value of
+     * e.g. `10` accounts for `10%` of work done).
+     * Note that currently only `ProgressLocation.Notification` is capable of showing discrete progress.
+     *
+     * To monitor if the operation has been cancelled by the user, use the provided [`CancellationToken`](#CancellationToken).
+     * Note that currently only `ProgressLocation.Notification` is supporting to show a cancel button to cancel the
+     * long running operation.
+     *
+     * @return The thenable the task-callback returned.
+     */
+    withProgress<R>(options: ProgressOptions, task: (progress: Progress<{ message?: string; increment?: number }>, token: CancellationToken) => Thenable<R>): Thenable<R>;
 }
 
 export const ICommandManager = Symbol('ICommandManager');
diff --git a/src/client/common/editor.ts b/src/client/common/editor.ts
index 8f70a2714f48..696b3b90fe63 100644
--- a/src/client/common/editor.ts
+++ b/src/client/common/editor.ts
@@ -158,7 +158,7 @@ function getTextEditsInternal(before: string, diffs: [number, string][], startLi
     let line = startLine;
     let character = 0;
     if (line > 0) {
-        const beforeLines = <string[]>before.split(/\r?\n/g);
+        const beforeLines = before.split(/\r?\n/g);
         beforeLines.filter((l, i) => i < line).forEach(l => character += l.length + NEW_LINE_LENGTH);
     }
     const edits: Edit[] = [];
diff --git a/src/client/common/envFileParser.ts b/src/client/common/envFileParser.ts
index 18ac1655ee51..52d2234c21b8 100644
--- a/src/client/common/envFileParser.ts
+++ b/src/client/common/envFileParser.ts
@@ -9,7 +9,7 @@ function parseEnvironmentVariables(contents: string): EnvironmentVariables | und
         return undefined;
     }
 
-    const env = {} as EnvironmentVariables;
+    const env: EnvironmentVariables = {};
     contents.split('\n').forEach(line => {
         const match = line.match(/^\s*([\w\.\-]+)\s*=\s*(.*)?\s*$/);
         if (match !== null) {
@@ -40,7 +40,9 @@ export function parseEnvFile(envFile: string, mergeWithProcessEnvVars: boolean =
 export function mergeEnvVariables(targetEnvVars: EnvironmentVariables, sourceEnvVars: EnvironmentVariables = process.env): EnvironmentVariables {
     const service = new EnvironmentVariablesService(new PathUtils(IS_WINDOWS));
     service.mergeVariables(sourceEnvVars, targetEnvVars);
-    service.appendPythonPath(targetEnvVars, sourceEnvVars.PYTHONPATH);
+    if (sourceEnvVars.PYTHONPATH) {
+        service.appendPythonPath(targetEnvVars, sourceEnvVars.PYTHONPATH);
+    }
     return targetEnvVars;
 }
 
@@ -57,6 +59,6 @@ export function mergePythonPath(env: EnvironmentVariables, currentPythonPath: st
         return env;
     }
     const service = new EnvironmentVariablesService(new PathUtils(IS_WINDOWS));
-    service.appendPythonPath(env, currentPythonPath!);
+    service.appendPythonPath(env, currentPythonPath);
     return env;
 }
diff --git a/src/client/common/installer/channelManager.ts b/src/client/common/installer/channelManager.ts
index 7c5780d9152e..d145f6216b10 100644
--- a/src/client/common/installer/channelManager.ts
+++ b/src/client/common/installer/channelManager.ts
@@ -41,13 +41,13 @@ export class InstallationChannelManager implements IInstallationChannelManager {
     }
 
     public async getInstallationChannels(resource?: Uri): Promise<IModuleInstaller[]> {
-        let installers = this.serviceContainer.getAll<IModuleInstaller>(IModuleInstaller);
+        const installers = this.serviceContainer.getAll<IModuleInstaller>(IModuleInstaller);
         const supportedInstallers: IModuleInstaller[] = [];
         if (installers.length === 0) {
             return [];
         }
         // group by priority and pick supported from the highest priority
-        installers = installers.sort((a, b) => b.priority - a.priority);
+        installers.sort((a, b) => b.priority - a.priority);
         let currentPri = installers[0].priority;
         for (const mi of installers) {
             if (mi.priority !== currentPri) {
diff --git a/src/client/common/utils/async.ts b/src/client/common/utils/async.ts
index ed7d6b4869cf..9c5c53dc7892 100644
--- a/src/client/common/utils/async.ts
+++ b/src/client/common/utils/async.ts
@@ -64,3 +64,12 @@ class DeferredImpl<T> implements Deferred<T> {
 export function createDeferred<T>(scope: any = null): Deferred<T> {
     return new DeferredImpl<T>(scope);
 }
+
+export function createDeferredFrom<T>(...promises: Promise<T>[]): Deferred<T> {
+    const deferred = createDeferred<T>();
+    Promise.all(promises)
+        .then(deferred.resolve.bind(deferred))
+        .catch(deferred.reject.bind(deferred));
+
+    return deferred;
+}
diff --git a/src/client/common/utils/localize.ts b/src/client/common/utils/localize.ts
index 107a1c0a0d51..b3a5a5bad690 100644
--- a/src/client/common/utils/localize.ts
+++ b/src/client/common/utils/localize.ts
@@ -14,6 +14,10 @@ export namespace LanguageServiceSurveyBanner {
     export const bannerLabelNo = localize('LanguageServiceSurveyBanner.bannerLabelNo', 'No, thanks');
 }
 
+export namespace Interpreters {
+    export const refreshing = localize('Interpreters.RefreshingInterpreters', 'Refreshing Python Interpreters');
+}
+
 export namespace DataScience {
     export const historyTitle = localize('DataScience.historyTitle', 'Python Interactive');
     export const badWebPanelFormatString = localize('DataScience.badWebPanelFormatString', '<html><body><h1>{0} is not a valid file name</h1></body></html>');
diff --git a/src/client/debugger/extension/configProviders/baseProvider.ts b/src/client/debugger/extension/configProviders/baseProvider.ts
index 04d34d0a15fc..ad7a65769a07 100644
--- a/src/client/debugger/extension/configProviders/baseProvider.ts
+++ b/src/client/debugger/extension/configProviders/baseProvider.ts
@@ -68,7 +68,7 @@ export abstract class BaseConfigurationProvider implements DebugConfigurationPro
             debugConfiguration.cwd = workspaceFolder.fsPath;
         }
         if (typeof debugConfiguration.envFile !== 'string' && workspaceFolder) {
-            const envFile = workspaceFolder ? path.join(workspaceFolder.fsPath, '.env') : '';
+            const envFile = path.join(workspaceFolder.fsPath, '.env');
             debugConfiguration.envFile = envFile;
         }
         if (typeof debugConfiguration.stopOnEntry !== 'boolean') {
diff --git a/src/client/extension.ts b/src/client/extension.ts
index 1a609546f089..084608a018aa 100644
--- a/src/client/extension.ts
+++ b/src/client/extension.ts
@@ -41,7 +41,7 @@ import { registerTypes as debugConfigurationRegisterTypes } from './debugger/ext
 import { IDebugConfigurationProvider, IDebuggerBanner } from './debugger/extension/types';
 import { registerTypes as formattersRegisterTypes } from './formatters/serviceRegistry';
 import { IInterpreterSelector } from './interpreter/configuration/types';
-import { ICondaService, IInterpreterService, PythonInterpreter } from './interpreter/contracts';
+import { ICondaService, IInterpreterLocatorProgressService, IInterpreterService, InterpreterLocatorProgressHandler, PythonInterpreter } from './interpreter/contracts';
 import { registerTypes as interpretersRegisterTypes } from './interpreter/serviceRegistry';
 import { ServiceContainer } from './ioc/container';
 import { ServiceManager } from './ioc/serviceManager';
@@ -102,7 +102,8 @@ export async function activate(context: ExtensionContext): Promise<IExtensionApi
     serviceManager.get<ICodeExecutionManager>(ICodeExecutionManager).registerCommands();
     sendStartupTelemetry(activationDeferred.promise, serviceContainer).ignoreErrors();
 
-    interpreterManager.refresh()
+    const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
+    interpreterManager.refresh(workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders![0].uri : undefined)
         .catch(ex => console.error('Python Extension: interpreterManager.refresh', ex));
 
     const jupyterExtension = extensions.getExtension('donjayamanne.jupyter');
@@ -214,6 +215,9 @@ function initializeServices(context: ExtensionContext, serviceManager: ServiceMa
     const disposables = serviceManager.get<IDisposableRegistry>(IDisposableRegistry);
     const dispatcher = new DebugSessionEventDispatcher(handlers, DebugService.instance, disposables);
     dispatcher.registerEventHandlers();
+
+    serviceManager.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
+    serviceManager.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();
 }
 
 async function sendStartupTelemetry(activatedPromise: Promise<void>, serviceContainer: IServiceContainer) {
@@ -224,12 +228,13 @@ async function sendStartupTelemetry(activatedPromise: Promise<void>, serviceCont
         const terminalShellType = terminalHelper.identifyTerminalShell(terminalHelper.getTerminalShellPath());
         const condaLocator = serviceContainer.get<ICondaService>(ICondaService);
         const interpreterService = serviceContainer.get<IInterpreterService>(IInterpreterService);
+        const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
+        const mainWorkspaceUri = workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders![0].uri : undefined;
         const [condaVersion, interpreter, interpreters] = await Promise.all([
             condaLocator.getCondaVersion().then(ver => ver ? ver.raw : '').catch<string>(() => ''),
             interpreterService.getActiveInterpreter().catch<PythonInterpreter | undefined>(() => undefined),
-            interpreterService.getInterpreters().catch<PythonInterpreter[]>(() => [])
+            interpreterService.getInterpreters(mainWorkspaceUri).catch<PythonInterpreter[]>(() => [])
         ]);
-        const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
         const workspaceFolderCount = workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders!.length : 0;
         const pythonVersion = interpreter ? interpreter.version_info.join('.') : undefined;
         const interpreterType = interpreter ? interpreter.type : undefined;
diff --git a/src/client/interpreter/contracts.ts b/src/client/interpreter/contracts.ts
index e687ab557bd2..932b3abceb4c 100644
--- a/src/client/interpreter/contracts.ts
+++ b/src/client/interpreter/contracts.ts
@@ -28,6 +28,7 @@ export interface IVirtualEnvironmentsSearchPathProvider {
 export const IInterpreterLocatorService = Symbol('IInterpreterLocatorService');
 
 export interface IInterpreterLocatorService extends Disposable {
+    readonly onLocating: Event<Promise<PythonInterpreter[]>>;
     getInterpreters(resource?: Uri): Promise<PythonInterpreter[]>;
 }
 
@@ -83,7 +84,7 @@ export interface IInterpreterService {
     autoSetInterpreter(): Promise<void>;
     getActiveInterpreter(resource?: Uri): Promise<PythonInterpreter | undefined>;
     getInterpreterDetails(pythonPath: string, resoure?: Uri): Promise<undefined | PythonInterpreter>;
-    refresh(): Promise<void>;
+    refresh(resource: Uri | undefined): Promise<void>;
     initialize(): void;
     getDisplayName(interpreter: Partial<PythonInterpreter>): Promise<string>;
     shouldAutoSetInterpreter(): Promise<boolean>;
@@ -126,3 +127,15 @@ export const IInterpreterWatcherBuilder = Symbol('IInterpreterWatcherBuilder');
 export interface IInterpreterWatcherBuilder {
     getWorkspaceVirtualEnvInterpreterWatcher(resource: Uri | undefined): Promise<IInterpreterWatcher>;
 }
+
+export const InterpreterLocatorProgressHandler = Symbol('InterpreterLocatorProgressHandler');
+export interface InterpreterLocatorProgressHandler {
+    register(): void;
+}
+
+export const IInterpreterLocatorProgressService = Symbol('IInterpreterLocatorProgressService');
+export interface IInterpreterLocatorProgressService {
+    readonly onRefreshing: Event<void>;
+    readonly onRefreshed: Event<void>;
+    register(): void;
+}
diff --git a/src/client/interpreter/display/progressDisplay.ts b/src/client/interpreter/display/progressDisplay.ts
new file mode 100644
index 000000000000..07d0a1da6ddb
--- /dev/null
+++ b/src/client/interpreter/display/progressDisplay.ts
@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+'use strict';
+
+import { inject, injectable } from 'inversify';
+import { Disposable, ProgressLocation, ProgressOptions } from 'vscode';
+import { IApplicationShell } from '../../common/application/types';
+import { traceVerbose } from '../../common/logger';
+import { IDisposableRegistry } from '../../common/types';
+import { createDeferred, Deferred } from '../../common/utils/async';
+import { Interpreters } from '../../common/utils/localize';
+import { IInterpreterLocatorProgressService, InterpreterLocatorProgressHandler } from '../contracts';
+
+const progressOptions: ProgressOptions = { location: ProgressLocation.Window, title: Interpreters.refreshing() };
+
+@injectable()
+export class InterpreterLocatorProgressStatubarHandler implements InterpreterLocatorProgressHandler {
+    private deferred: Deferred<void> | undefined;
+    constructor(@inject(IApplicationShell) private readonly shell: IApplicationShell,
+        @inject(IInterpreterLocatorProgressService) private readonly progressService: IInterpreterLocatorProgressService,
+        @inject(IDisposableRegistry) private readonly disposables: Disposable[]) { }
+    public register() {
+        this.progressService.onRefreshing(() => this.showProgress(), this, this.disposables);
+        this.progressService.onRefreshed(() => this.hideProgress(), this, this.disposables);
+    }
+    @traceVerbose('Display locator refreshing progress')
+    private showProgress(): void {
+        if (!this.deferred) {
+            this.createProgress();
+        }
+    }
+    @traceVerbose('Hide locator refreshing progress')
+    private hideProgress(): void {
+        if (this.deferred) {
+            this.deferred.resolve();
+            this.deferred = undefined;
+        }
+    }
+    private createProgress() {
+        this.shell.withProgress(progressOptions, () => {
+            this.deferred = createDeferred();
+            return this.deferred.promise;
+        });
+    }
+}
diff --git a/src/client/interpreter/interpreterService.ts b/src/client/interpreter/interpreterService.ts
index 11e1ebeeff65..430e1c4140a4 100644
--- a/src/client/interpreter/interpreterService.ts
+++ b/src/client/interpreter/interpreterService.ts
@@ -81,7 +81,8 @@ export class InterpreterService implements Disposable, IInterpreterService {
             return;
         }
         // Always pick the highest version by default.
-        const pythonPath = interpretersInWorkspace.sort((a, b) => a.version! > b.version! ? 1 : -1)[0].path;
+        interpretersInWorkspace.sort((a, b) => a.version! > b.version! ? 1 : -1);
+        const pythonPath = interpretersInWorkspace[0].path;
         // Ensure this new environment is at the same level as the current workspace.
         // In windows the interpreter is under scripts/python.exe on linux it is under bin/python.
         // Meaning the sub directory must be either scripts, bin or other (but only one level deep).
diff --git a/src/client/interpreter/locators/index.ts b/src/client/interpreter/locators/index.ts
index 521b099a588a..b922b1376252 100644
--- a/src/client/interpreter/locators/index.ts
+++ b/src/client/interpreter/locators/index.ts
@@ -1,6 +1,6 @@
 import { inject, injectable } from 'inversify';
 import * as _ from 'lodash';
-import { Disposable, Uri } from 'vscode';
+import { Disposable, Event, EventEmitter, Uri } from 'vscode';
 import { IPlatformService } from '../../common/platform/types';
 import { IDisposableRegistry } from '../../common/types';
 import { IServiceContainer } from '../../ioc/types';
@@ -26,7 +26,6 @@ export class PythonInterpreterLocatorService implements IInterpreterLocatorServi
     private readonly disposables: Disposable[] = [];
     private readonly platform: IPlatformService;
     private readonly interpreterLocatorHelper: IInterpreterLocatorHelper;
-
     constructor(
         @inject(IServiceContainer) private serviceContainer: IServiceContainer
     ) {
@@ -34,6 +33,17 @@ export class PythonInterpreterLocatorService implements IInterpreterLocatorServi
         this.platform = serviceContainer.get<IPlatformService>(IPlatformService);
         this.interpreterLocatorHelper = serviceContainer.get<IInterpreterLocatorHelper>(IInterpreterLocatorHelper);
     }
+    /**
+     * This class should never emit events when we're locating.
+     * The events will be fired by the indivitual locators retrieved in `getLocators`.
+     *
+     * @readonly
+     * @type {Event<Promise<PythonInterpreter[]>>}
+     * @memberof PythonInterpreterLocatorService
+     */
+    public get onLocating(): Event<Promise<PythonInterpreter[]>> {
+        return new EventEmitter<Promise<PythonInterpreter[]>>().event;
+    }
 
     /**
      * Release any held resources.
diff --git a/src/client/interpreter/locators/progressService.ts b/src/client/interpreter/locators/progressService.ts
new file mode 100644
index 000000000000..cddec2f665c3
--- /dev/null
+++ b/src/client/interpreter/locators/progressService.ts
@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+'use strict';
+
+import { inject, injectable } from 'inversify';
+import { Disposable, Event, EventEmitter } from 'vscode';
+import { traceVerbose } from '../../common/logger';
+import { IDisposableRegistry } from '../../common/types';
+import { createDeferredFrom, Deferred } from '../../common/utils/async';
+import { noop } from '../../common/utils/misc';
+import { IServiceContainer } from '../../ioc/types';
+import { IInterpreterLocatorProgressService, IInterpreterLocatorService, PythonInterpreter } from '../contracts';
+
+@injectable()
+export class InterpreterLocatorProgressService implements IInterpreterLocatorProgressService {
+    private deferreds: Deferred<PythonInterpreter[]>[] = [];
+    private readonly refreshing = new EventEmitter<void>();
+    private readonly refreshed = new EventEmitter<void>();
+    private readonly locators: IInterpreterLocatorService[] = [];
+    constructor(@inject(IServiceContainer) serviceContainer: IServiceContainer,
+        @inject(IDisposableRegistry) private readonly disposables: Disposable[]) {
+        this.locators = serviceContainer.getAll<IInterpreterLocatorService>(IInterpreterLocatorService);
+    }
+
+    public get onRefreshing(): Event<void> {
+        return this.refreshing.event;
+    }
+    public get onRefreshed(): Event<void> {
+        return this.refreshed.event;
+    }
+    public register(): void {
+        this.locators.forEach(locator => {
+            locator.onLocating(this.handleProgress, this, this.disposables);
+        });
+    }
+    @traceVerbose('Detected refreshing of Interpreters')
+    private handleProgress(promise: Promise<PythonInterpreter[]>) {
+        this.deferreds.push(createDeferredFrom(promise));
+        this.notifyRefreshing();
+        this.checkProgress();
+    }
+    @traceVerbose('All locators have completed locating')
+    private notifyCompleted() {
+        this.refreshed.fire();
+    }
+    @traceVerbose('Notify locators are locating')
+    private notifyRefreshing() {
+        this.refreshing.fire();
+    }
+    @traceVerbose('Checking whether locactors have completed locating')
+    private checkProgress() {
+        if (this.areAllItemsCcomplete()) {
+            return this.notifyCompleted();
+        }
+        Promise.all(this.deferreds.map(item => item.promise))
+            .catch(noop)
+            .then(() => this.checkProgress())
+            .ignoreErrors();
+    }
+    private areAllItemsCcomplete() {
+        this.deferreds = this.deferreds.filter(item => !item.completed);
+        return this.deferreds.length === 0;
+    }
+}
diff --git a/src/client/interpreter/locators/services/cacheableLocatorService.ts b/src/client/interpreter/locators/services/cacheableLocatorService.ts
index ecac28ee6d33..7e2d8bed685b 100644
--- a/src/client/interpreter/locators/services/cacheableLocatorService.ts
+++ b/src/client/interpreter/locators/services/cacheableLocatorService.ts
@@ -5,7 +5,7 @@
 
 import { injectable, unmanaged } from 'inversify';
 import * as md5 from 'md5';
-import { Disposable, Uri } from 'vscode';
+import { Disposable, Event, EventEmitter, Uri } from 'vscode';
 import { IWorkspaceService } from '../../../common/application/types';
 import '../../../common/extensions';
 import { Logger } from '../../../common/logger';
@@ -19,11 +19,15 @@ export abstract class CacheableLocatorService implements IInterpreterLocatorServ
     private readonly promisesPerResource = new Map<string, Deferred<PythonInterpreter[]>>();
     private readonly handlersAddedToResource = new Set<string>();
     private readonly cacheKeyPrefix: string;
+    private readonly locating = new EventEmitter<Promise<PythonInterpreter[]>>();
     constructor(@unmanaged() name: string,
         @unmanaged() protected readonly serviceContainer: IServiceContainer,
         @unmanaged() private cachePerWorkspace: boolean = false) {
         this.cacheKeyPrefix = `INTERPRETERS_CACHE_v2_${name}`;
     }
+    public get onLocating(): Event<Promise<PythonInterpreter[]>> {
+        return this.locating.event;
+    }
     public abstract dispose();
     public async getInterpreters(resource?: Uri): Promise<PythonInterpreter[]> {
         const cacheKey = this.getCacheKey(resource);
@@ -42,6 +46,8 @@ export abstract class CacheableLocatorService implements IInterpreterLocatorServ
                     deferred!.resolve(items);
                 })
                 .catch(ex => deferred!.reject(ex));
+
+            this.locating.fire(deferred.promise);
         }
         if (deferred.completed) {
             return deferred.promise;
diff --git a/src/client/interpreter/serviceRegistry.ts b/src/client/interpreter/serviceRegistry.ts
index e3828d174dd2..12ea7771f6bd 100644
--- a/src/client/interpreter/serviceRegistry.ts
+++ b/src/client/interpreter/serviceRegistry.ts
@@ -17,6 +17,7 @@ import {
     IInterpreterDisplay,
     IInterpreterHelper,
     IInterpreterLocatorHelper,
+    IInterpreterLocatorProgressService,
     IInterpreterLocatorService,
     IInterpreterService,
     IInterpreterVersionService,
@@ -24,6 +25,7 @@ import {
     IInterpreterWatcherBuilder,
     IKnownSearchPathsForInterpreters,
     INTERPRETER_LOCATOR_SERVICE,
+    InterpreterLocatorProgressHandler,
     IPipEnvService,
     IShebangCodeLensProvider,
     IVirtualEnvironmentsSearchPathProvider,
@@ -33,12 +35,14 @@ import {
     WORKSPACE_VIRTUAL_ENV_SERVICE
 } from './contracts';
 import { InterpreterDisplay } from './display';
+import { InterpreterLocatorProgressStatubarHandler } from './display/progressDisplay';
 import { ShebangCodeLensProvider } from './display/shebangCodeLensProvider';
 import { InterpreterHelper } from './helpers';
 import { InterpreterService } from './interpreterService';
 import { InterpreterVersionService } from './interpreterVersion';
 import { InterpreterLocatorHelper } from './locators/helpers';
 import { PythonInterpreterLocatorService } from './locators/index';
+import { InterpreterLocatorProgressService } from './locators/progressService';
 import { CondaEnvFileService } from './locators/services/condaEnvFileService';
 import { CondaEnvService } from './locators/services/condaEnvService';
 import { CondaService } from './locators/services/condaService';
@@ -90,4 +94,7 @@ export function registerTypes(serviceManager: IServiceManager) {
     serviceManager.addSingleton<IInterpreterHelper>(IInterpreterHelper, InterpreterHelper);
     serviceManager.addSingleton<IInterpreterLocatorHelper>(IInterpreterLocatorHelper, InterpreterLocatorHelper);
     serviceManager.addSingleton<IInterpreterComparer>(IInterpreterComparer, InterpreterComparer);
+
+    serviceManager.addSingleton<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler, InterpreterLocatorProgressStatubarHandler);
+    serviceManager.addSingleton<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService, InterpreterLocatorProgressService);
 }
diff --git a/src/client/typeFormatters/dispatcher.ts b/src/client/typeFormatters/dispatcher.ts
index 0470b28c902d..86c22bc60d47 100644
--- a/src/client/typeFormatters/dispatcher.ts
+++ b/src/client/typeFormatters/dispatcher.ts
@@ -23,8 +23,8 @@ export class OnTypeFormattingDispatcher implements OnTypeFormattingEditProvider
     }
 
     public getTriggerCharacters(): { first: string; more: string[] } | undefined {
-        let keys = Object.keys(this.providers);
-        keys = keys.sort(); // Make output deterministic
+        const keys = Object.keys(this.providers);
+        keys.sort(); // Make output deterministic
 
         const first = keys.shift();
 
diff --git a/src/client/unittests/unittest/helper.ts b/src/client/unittests/unittest/helper.ts
index a97aed3102cf..f89c4c287b39 100644
--- a/src/client/unittests/unittest/helper.ts
+++ b/src/client/unittests/unittest/helper.ts
@@ -30,7 +30,7 @@ export class UnitTestHelper implements IUnitTestHelper {
         const testIds: string[] = [];
         if (testsToRun && testsToRun.testFolder) {
             // Get test ids of files in these folders.
-            testsToRun.testFolder.map(folder => {
+            testsToRun.testFolder.forEach(folder => {
                 tests.testFiles.forEach(f => {
                     if (f.fullPath.startsWith(folder.name)) {
                         testIds.push(f.nameToRun);

From b027087afdc87b77d5d1e0dc5be4234aa370c082 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 09:54:28 -0700
Subject: [PATCH 10/16] Fix vsc fakes

---
 src/test/vscode-mock.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/test/vscode-mock.ts b/src/test/vscode-mock.ts
index 714fc9304485..904083ce8cf2 100644
--- a/src/test/vscode-mock.ts
+++ b/src/test/vscode-mock.ts
@@ -68,6 +68,7 @@ mockedVSCode.DocumentLink = vscodeMocks.vscMockExtHostedTypes.DocumentLink;
 mockedVSCode.TextEdit = vscodeMocks.vscMockExtHostedTypes.TextEdit;
 mockedVSCode.WorkspaceEdit = vscodeMocks.vscMockExtHostedTypes.WorkspaceEdit;
 mockedVSCode.RelativePattern = vscodeMocks.vscMockExtHostedTypes.RelativePattern;
+mockedVSCode.ProgressLocation = vscodeMocks.vscMockExtHostedTypes.ProgressLocation;
 
 // This API is used in src/client/telemetry/telemetry.ts
 const extensions = TypeMoq.Mock.ofType<typeof vscode.extensions>();

From e2d2b3a12ef4230229f07ca76788fa17493d0d17 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 10:00:35 -0700
Subject: [PATCH 11/16] Fix tests

---
 package.nls.json        |  3 ++-
 src/client/extension.ts | 11 +++++++----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/package.nls.json b/package.nls.json
index 1894c63a689e..41ea12af7718 100644
--- a/package.nls.json
+++ b/package.nls.json
@@ -78,5 +78,6 @@
     "DataScience.jupyterNotSupported" : "Jupyter is not installed",
     "DataScience.jupyterNbConvertNotSupported" : "Jupyter nbconvert is not installed",
     "DataScience.importingFormat" : "Importing {0}",
-    "DataScience.startingJupyter" : "Starting Jupyter backend"
+    "DataScience.startingJupyter" : "Starting Jupyter backend",
+    "Interpreters.RefreshingInterpreters" : "Refreshing Python Interpreters"
 }
diff --git a/src/client/extension.ts b/src/client/extension.ts
index 084608a018aa..f74fed0342d9 100644
--- a/src/client/extension.ts
+++ b/src/client/extension.ts
@@ -164,6 +164,8 @@ export async function activate(context: ExtensionContext): Promise<IExtensionApi
     durations.endActivateTime = stopWatch.elapsedTime;
     activationDeferred.resolve();
 
+    intializeServicesPostActivation(serviceContainer);
+
     const api = { ready: activationDeferred.promise };
     // In test environment return the DI Container.
     if (isTestExecution()) {
@@ -215,11 +217,12 @@ function initializeServices(context: ExtensionContext, serviceManager: ServiceMa
     const disposables = serviceManager.get<IDisposableRegistry>(IDisposableRegistry);
     const dispatcher = new DebugSessionEventDispatcher(handlers, DebugService.instance, disposables);
     dispatcher.registerEventHandlers();
-
-    serviceManager.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
-    serviceManager.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();
 }
-
+function intializeServicesPostActivation(serviceContainer: ServiceContainer) {
+    // Display progress of interpreter refreshes only after extension has activated.
+    serviceContainer.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
+    serviceContainer.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();
+}
 async function sendStartupTelemetry(activatedPromise: Promise<void>, serviceContainer: IServiceContainer) {
     const logger = serviceContainer.get<ILogger>(ILogger);
     try {

From 1dae216ba5f44fcf90654442e48b663f8e7f2a88 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 10:16:36 -0700
Subject: [PATCH 12/16] Refactor

---
 src/client/extension.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/client/extension.ts b/src/client/extension.ts
index f74fed0342d9..12a1823d851a 100644
--- a/src/client/extension.ts
+++ b/src/client/extension.ts
@@ -219,6 +219,12 @@ function initializeServices(context: ExtensionContext, serviceManager: ServiceMa
     dispatcher.registerEventHandlers();
 }
 function intializeServicesPostActivation(serviceContainer: ServiceContainer) {
+    // Get latest interpreter list.
+    const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
+    const mainWorkspaceUri = workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders![0].uri : undefined;
+    const interpreterService = serviceContainer.get<IInterpreterService>(IInterpreterService);
+    interpreterService.getInterpreters(mainWorkspaceUri).ignoreErrors();
+
     // Display progress of interpreter refreshes only after extension has activated.
     serviceContainer.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
     serviceContainer.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();

From b0b5c66124aee51357872323cde0208687e3dd3c Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 10:18:18 -0700
Subject: [PATCH 13/16] Refactor

---
 src/client/extension.ts | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/src/client/extension.ts b/src/client/extension.ts
index 12a1823d851a..ed27592ab1e1 100644
--- a/src/client/extension.ts
+++ b/src/client/extension.ts
@@ -164,8 +164,6 @@ export async function activate(context: ExtensionContext): Promise<IExtensionApi
     durations.endActivateTime = stopWatch.elapsedTime;
     activationDeferred.resolve();
 
-    intializeServicesPostActivation(serviceContainer);
-
     const api = { ready: activationDeferred.promise };
     // In test environment return the DI Container.
     if (isTestExecution()) {
@@ -217,8 +215,7 @@ function initializeServices(context: ExtensionContext, serviceManager: ServiceMa
     const disposables = serviceManager.get<IDisposableRegistry>(IDisposableRegistry);
     const dispatcher = new DebugSessionEventDispatcher(handlers, DebugService.instance, disposables);
     dispatcher.registerEventHandlers();
-}
-function intializeServicesPostActivation(serviceContainer: ServiceContainer) {
+
     // Get latest interpreter list.
     const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
     const mainWorkspaceUri = workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders![0].uri : undefined;

From c27a619a4280ec839b6383f9d03bde9b27aff012 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 10:22:11 -0700
Subject: [PATCH 14/16] Refactor again

---
 src/client/extension.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/client/extension.ts b/src/client/extension.ts
index ed27592ab1e1..88f7cd240083 100644
--- a/src/client/extension.ts
+++ b/src/client/extension.ts
@@ -216,15 +216,15 @@ function initializeServices(context: ExtensionContext, serviceManager: ServiceMa
     const dispatcher = new DebugSessionEventDispatcher(handlers, DebugService.instance, disposables);
     dispatcher.registerEventHandlers();
 
+    // Display progress of interpreter refreshes only after extension has activated.
+    serviceContainer.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
+    serviceContainer.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();
+
     // Get latest interpreter list.
     const workspaceService = serviceContainer.get<IWorkspaceService>(IWorkspaceService);
     const mainWorkspaceUri = workspaceService.hasWorkspaceFolders ? workspaceService.workspaceFolders![0].uri : undefined;
     const interpreterService = serviceContainer.get<IInterpreterService>(IInterpreterService);
     interpreterService.getInterpreters(mainWorkspaceUri).ignoreErrors();
-
-    // Display progress of interpreter refreshes only after extension has activated.
-    serviceContainer.get<InterpreterLocatorProgressHandler>(InterpreterLocatorProgressHandler).register();
-    serviceContainer.get<IInterpreterLocatorProgressService>(IInterpreterLocatorProgressService).register();
 }
 async function sendStartupTelemetry(activatedPromise: Promise<void>, serviceContainer: IServiceContainer) {
     const logger = serviceContainer.get<ILogger>(ILogger);

From 012b3a2a49ba55d103222d88e98bea69ba7450e3 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 10:37:25 -0700
Subject: [PATCH 15/16] Changes to message

---
 package.nls.json                              | 41 ++++++++++---------
 src/client/common/utils/localize.ts           |  1 +
 .../interpreter/display/progressDisplay.ts    |  8 +++-
 3 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/package.nls.json b/package.nls.json
index 41ea12af7718..d1013d8101ff 100644
--- a/package.nls.json
+++ b/package.nls.json
@@ -59,25 +59,26 @@
     "LanguageServiceSurveyBanner.bannerMessage": "Can you please take 2 minutes to tell us how the Python Language Server is working for you?",
     "LanguageServiceSurveyBanner.bannerLabelYes": "Yes, take survey now",
     "LanguageServiceSurveyBanner.bannerLabelNo": "No, thanks",
-    "DataScience.unknownMimeType" : "Unknown mime type for data",
-    "DataScience.historyTitle" : "Python Interactive",
+    "DataScience.unknownMimeType": "Unknown mime type for data",
+    "DataScience.historyTitle": "Python Interactive",
     "DataScience.badWebPanelFormatString": "<html><body><h1>{0} is not a valid file name</h1></body></html>",
-    "DataScience.sessionDisposed" : "Cannot execute code, session has been disposed.",
-	"DataScience.exportDialogTitle" : "Export to Jupyter Notebook",
-	"DataScience.exportDialogFilter" : "Jupyter Notebooks",
-	"DataScience.exportDialogComplete" : "Notebook written to {0}",
-	"DataScience.exportDialogFailed" : "Failed to export notebook. {0}",
-    "DataScience.exportOpenQuestion" : "Open in browser",
-    "DataScience.collapseInputTooltip" : "Collapse input block",
-    "DataScience.importDialogTitle" : "Import Jupyter Notebook",
-    "DataScience.importDialogFilter" : "Jupyter Notebooks",
-    "DataScience.notebookCheckForImportYes" : "Import",
-    "DataScience.notebookCheckForImportNo" : "Later",
-    "DataScience.notebookCheckForImportDontAskAgain" : "Don't Ask Again",
-    "DataScience.notebookCheckForImportTitle" : "Do you want to import the Jupyter Notebook into Python code?",
-    "DataScience.jupyterNotSupported" : "Jupyter is not installed",
-    "DataScience.jupyterNbConvertNotSupported" : "Jupyter nbconvert is not installed",
-    "DataScience.importingFormat" : "Importing {0}",
-    "DataScience.startingJupyter" : "Starting Jupyter backend",
-    "Interpreters.RefreshingInterpreters" : "Refreshing Python Interpreters"
+    "DataScience.sessionDisposed": "Cannot execute code, session has been disposed.",
+    "DataScience.exportDialogTitle": "Export to Jupyter Notebook",
+    "DataScience.exportDialogFilter": "Jupyter Notebooks",
+    "DataScience.exportDialogComplete": "Notebook written to {0}",
+    "DataScience.exportDialogFailed": "Failed to export notebook. {0}",
+    "DataScience.exportOpenQuestion": "Open in browser",
+    "DataScience.collapseInputTooltip": "Collapse input block",
+    "DataScience.importDialogTitle": "Import Jupyter Notebook",
+    "DataScience.importDialogFilter": "Jupyter Notebooks",
+    "DataScience.notebookCheckForImportYes": "Import",
+    "DataScience.notebookCheckForImportNo": "Later",
+    "DataScience.notebookCheckForImportDontAskAgain": "Don't Ask Again",
+    "DataScience.notebookCheckForImportTitle": "Do you want to import the Jupyter Notebook into Python code?",
+    "DataScience.jupyterNotSupported": "Jupyter is not installed",
+    "DataScience.jupyterNbConvertNotSupported": "Jupyter nbconvert is not installed",
+    "DataScience.importingFormat": "Importing {0}",
+    "DataScience.startingJupyter": "Starting Jupyter backend",
+    "Interpreters.RefreshingInterpreters": "Refreshing Python Interpreters",
+    "Interpreters.LoadingInterpreters": "Loading Python Interpreters"
 }
diff --git a/src/client/common/utils/localize.ts b/src/client/common/utils/localize.ts
index b3a5a5bad690..86a87663dcad 100644
--- a/src/client/common/utils/localize.ts
+++ b/src/client/common/utils/localize.ts
@@ -15,6 +15,7 @@ export namespace LanguageServiceSurveyBanner {
 }
 
 export namespace Interpreters {
+    export const loading = localize('Interpreters.LoadingInterpreters', 'Loading Python Interpreters');
     export const refreshing = localize('Interpreters.RefreshingInterpreters', 'Refreshing Python Interpreters');
 }
 
diff --git a/src/client/interpreter/display/progressDisplay.ts b/src/client/interpreter/display/progressDisplay.ts
index 07d0a1da6ddb..e41d49c30580 100644
--- a/src/client/interpreter/display/progressDisplay.ts
+++ b/src/client/interpreter/display/progressDisplay.ts
@@ -12,11 +12,10 @@ import { createDeferred, Deferred } from '../../common/utils/async';
 import { Interpreters } from '../../common/utils/localize';
 import { IInterpreterLocatorProgressService, InterpreterLocatorProgressHandler } from '../contracts';
 
-const progressOptions: ProgressOptions = { location: ProgressLocation.Window, title: Interpreters.refreshing() };
-
 @injectable()
 export class InterpreterLocatorProgressStatubarHandler implements InterpreterLocatorProgressHandler {
     private deferred: Deferred<void> | undefined;
+    private isFirstTimeLoadingInterpreters = true;
     constructor(@inject(IApplicationShell) private readonly shell: IApplicationShell,
         @inject(IInterpreterLocatorProgressService) private readonly progressService: IInterpreterLocatorProgressService,
         @inject(IDisposableRegistry) private readonly disposables: Disposable[]) { }
@@ -38,6 +37,11 @@ export class InterpreterLocatorProgressStatubarHandler implements InterpreterLoc
         }
     }
     private createProgress() {
+        const progressOptions: ProgressOptions = {
+            location: ProgressLocation.Window,
+            title: this.isFirstTimeLoadingInterpreters ? Interpreters.loading() : Interpreters.refreshing()
+        };
+        this.isFirstTimeLoadingInterpreters = false;
         this.shell.withProgress(progressOptions, () => {
             this.deferred = createDeferred();
             return this.deferred.promise;

From 4938992db5674b1c820c9f7e035b55df375c369b Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@yahoo.com>
Date: Thu, 1 Nov 2018 11:54:50 -0700
Subject: [PATCH 16/16] Added tests

---
 .../display/progressDisplay.unit.test.ts      |  84 ++++++++++++++
 .../cacheableLocatorService.unit.test.ts      |  18 +++
 .../locators/progressService.unit.test.ts     | 109 ++++++++++++++++++
 3 files changed, 211 insertions(+)
 create mode 100644 src/test/interpreters/display/progressDisplay.unit.test.ts
 create mode 100644 src/test/interpreters/locators/progressService.unit.test.ts

diff --git a/src/test/interpreters/display/progressDisplay.unit.test.ts b/src/test/interpreters/display/progressDisplay.unit.test.ts
new file mode 100644
index 000000000000..1d09ee3d0be0
--- /dev/null
+++ b/src/test/interpreters/display/progressDisplay.unit.test.ts
@@ -0,0 +1,84 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+'use strict';
+
+// tslint:disable:no-any
+
+import { expect } from 'chai';
+import { anything, capture, instance, mock, when } from 'ts-mockito';
+import { CancellationToken, Disposable, Progress, ProgressOptions } from 'vscode';
+import { ApplicationShell } from '../../../client/common/application/applicationShell';
+import { Interpreters } from '../../../client/common/utils/localize';
+import { noop } from '../../../client/common/utils/misc';
+import { IInterpreterLocatorProgressService } from '../../../client/interpreter/contracts';
+import { InterpreterLocatorProgressStatubarHandler } from '../../../client/interpreter/display/progressDisplay';
+
+type ProgressTask<R> = (progress: Progress<{ message?: string; increment?: number }>, token: CancellationToken) => Thenable<R>;
+
+suite('Interpreters - Display Progress', () => {
+    let refreshingCallback: (e: void) => any | undefined;
+    let refreshedCallback: (e: void) => any | undefined;
+    const progressService: IInterpreterLocatorProgressService = {
+        onRefreshing(listener: (e: void) => any): Disposable {
+            refreshingCallback = listener;
+            return { dispose: noop };
+        },
+        onRefreshed(listener: (e: void) => any): Disposable {
+            refreshedCallback = listener;
+            return { dispose: noop };
+        },
+        register(): void {
+            noop();
+        }
+    };
+
+    test('Display loading message when refreshing interpreters for the first time', async () => {
+        const shell = mock(ApplicationShell);
+        const statusBar = new InterpreterLocatorProgressStatubarHandler(instance(shell), progressService, []);
+        when(shell.withProgress(anything(), anything())).thenResolve();
+
+        statusBar.register();
+        refreshingCallback(undefined);
+
+        const options = capture(shell.withProgress as any).last()[0] as ProgressOptions;
+        expect(options.title).to.be.equal(Interpreters.loading());
+    });
+
+    test('Display refreshing message when refreshing interpreters for the second time', async () => {
+        const shell = mock(ApplicationShell);
+        const statusBar = new InterpreterLocatorProgressStatubarHandler(instance(shell), progressService, []);
+        when(shell.withProgress(anything(), anything())).thenResolve();
+
+        statusBar.register();
+        refreshingCallback(undefined);
+
+        let options = capture(shell.withProgress as any).last()[0] as ProgressOptions;
+        expect(options.title).to.be.equal(Interpreters.loading());
+
+        refreshingCallback(undefined);
+
+        options = capture(shell.withProgress as any).last()[0] as ProgressOptions;
+        expect(options.title).to.be.equal(Interpreters.refreshing());
+    });
+
+    test('Progress message is hidden when loading has completed', async () => {
+        const shell = mock(ApplicationShell);
+        const statusBar = new InterpreterLocatorProgressStatubarHandler(instance(shell), progressService, []);
+        when(shell.withProgress(anything(), anything())).thenResolve();
+
+        statusBar.register();
+        refreshingCallback(undefined);
+
+        const options = capture(shell.withProgress as any).last()[0] as ProgressOptions;
+        const callback = capture(shell.withProgress as any).last()[1] as ProgressTask<void>;
+        const promise = callback(undefined as any, undefined as any);
+
+        expect(options.title).to.be.equal(Interpreters.loading());
+
+        refreshedCallback(undefined);
+        // Promise must resolve when refreshed callback is invoked.
+        // When promise resolves, the progress message is hidden by VSC.
+        await promise;
+    });
+});
diff --git a/src/test/interpreters/locators/cacheableLocatorService.unit.test.ts b/src/test/interpreters/locators/cacheableLocatorService.unit.test.ts
index 9851443aa019..1d0a210c26ca 100644
--- a/src/test/interpreters/locators/cacheableLocatorService.unit.test.ts
+++ b/src/test/interpreters/locators/cacheableLocatorService.unit.test.ts
@@ -145,6 +145,24 @@ suite('Interpreters - Cacheable Locator Service', () => {
             verify(mockedLocatorForVerification.getInterpretersImplementation()).twice();
             verify(mockedLocatorForVerification.cacheInterpreters()).twice();
         });
+        test('Ensure locating event is raised', async () => {
+            const mockedLocatorForVerification = mock(MockLocator);
+            const locator = new class extends Locator {
+                protected async getInterpreterWatchers(_resource: Uri | undefined): Promise<IInterpreterWatcher[]> {
+                    return [];
+                }
+            }('dummy', instance(serviceContainer), instance(mockedLocatorForVerification));
+
+            let locatingEventRaised = false;
+            locator.onLocating(() => locatingEventRaised = true);
+
+            when(mockedLocatorForVerification.getInterpretersImplementation()).thenResolve([1, 2] as any);
+            when(mockedLocatorForVerification.getCacheKey()).thenReturn('xyz');
+            when(mockedLocatorForVerification.getCachedInterpreters()).thenResolve();
+
+            await locator.getInterpreters();
+            expect(locatingEventRaised).to.be.equal(true, 'Locating Event not raised');
+        });
     });
     suite('Cache Key', () => {
         class Locator extends CacheableLocatorService {
diff --git a/src/test/interpreters/locators/progressService.unit.test.ts b/src/test/interpreters/locators/progressService.unit.test.ts
new file mode 100644
index 000000000000..6551f655e44a
--- /dev/null
+++ b/src/test/interpreters/locators/progressService.unit.test.ts
@@ -0,0 +1,109 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+'use strict';
+
+// tslint:disable:no-any max-classes-per-file max-func-body-length
+
+import { expect } from 'chai';
+import { anything, instance, mock, when } from 'ts-mockito';
+import { Disposable, Uri } from 'vscode';
+import { createDeferred } from '../../../client/common/utils/async';
+import { noop } from '../../../client/common/utils/misc';
+import { IInterpreterLocatorService, PythonInterpreter } from '../../../client/interpreter/contracts';
+import { InterpreterLocatorProgressService } from '../../../client/interpreter/locators/progressService';
+import { ServiceContainer } from '../../../client/ioc/container';
+import { sleep } from '../../core';
+
+suite('Interpreters - Locator Progress', () => {
+    class Locator implements IInterpreterLocatorService {
+        public locatingCallback?: (e: Promise<PythonInterpreter[]>) => any;
+        public onLocating(listener: (e: Promise<PythonInterpreter[]>) => any, thisArgs?: any, disposables?: Disposable[]): Disposable {
+            this.locatingCallback = listener;
+            return { dispose: noop };
+        }
+        public getInterpreters(resource?: Uri): Promise<PythonInterpreter[]> {
+            return Promise.resolve([]);
+        }
+        public dispose() {
+            noop();
+        }
+    }
+
+    test('Must raise refreshing event', async () => {
+        const serviceContainer = mock(ServiceContainer);
+        const locator = new Locator();
+        when(serviceContainer.getAll(anything())).thenReturn([locator]);
+        const progress = new InterpreterLocatorProgressService(instance(serviceContainer), []);
+        progress.register();
+
+        let refreshingInvoked = false;
+        progress.onRefreshing(() => refreshingInvoked = true);
+        let refreshedInvoked = false;
+        progress.onRefreshed(() => refreshedInvoked = true);
+
+        const locatingDeferred = createDeferred<PythonInterpreter[]>();
+        locator.locatingCallback!.bind(progress)(locatingDeferred.promise);
+        expect(refreshingInvoked).to.be.equal(true, 'Refreshing Not invoked');
+        expect(refreshedInvoked).to.be.equal(false, 'Refreshed invoked');
+    });
+    test('Must raise refreshed event', async () => {
+        const serviceContainer = mock(ServiceContainer);
+        const locator = new Locator();
+        when(serviceContainer.getAll(anything())).thenReturn([locator]);
+        const progress = new InterpreterLocatorProgressService(instance(serviceContainer), []);
+        progress.register();
+
+        let refreshingInvoked = false;
+        progress.onRefreshing(() => refreshingInvoked = true);
+        let refreshedInvoked = false;
+        progress.onRefreshed(() => refreshedInvoked = true);
+
+        const locatingDeferred = createDeferred<PythonInterpreter[]>();
+        locator.locatingCallback!.bind(progress)(locatingDeferred.promise);
+        locatingDeferred.resolve();
+
+        await sleep(10);
+        expect(refreshingInvoked).to.be.equal(true, 'Refreshing Not invoked');
+        expect(refreshedInvoked).to.be.equal(true, 'Refreshed not invoked');
+    });
+    test('Must raise refreshed event only when all locators have completed', async () => {
+        const serviceContainer = mock(ServiceContainer);
+        const locator1 = new Locator();
+        const locator2 = new Locator();
+        const locator3 = new Locator();
+        when(serviceContainer.getAll(anything())).thenReturn([locator1, locator2, locator3]);
+        const progress = new InterpreterLocatorProgressService(instance(serviceContainer), []);
+        progress.register();
+
+        let refreshingInvoked = false;
+        progress.onRefreshing(() => refreshingInvoked = true);
+        let refreshedInvoked = false;
+        progress.onRefreshed(() => refreshedInvoked = true);
+
+        const locatingDeferred1 = createDeferred<PythonInterpreter[]>();
+        locator1.locatingCallback!.bind(progress)(locatingDeferred1.promise);
+
+        const locatingDeferred2 = createDeferred<PythonInterpreter[]>();
+        locator2.locatingCallback!.bind(progress)(locatingDeferred2.promise);
+
+        const locatingDeferred3 = createDeferred<PythonInterpreter[]>();
+        locator3.locatingCallback!.bind(progress)(locatingDeferred3.promise);
+
+        locatingDeferred1.resolve();
+
+        await sleep(10);
+        expect(refreshingInvoked).to.be.equal(true, 'Refreshing Not invoked');
+        expect(refreshedInvoked).to.be.equal(false, 'Refreshed invoked');
+
+        locatingDeferred2.resolve();
+
+        await sleep(10);
+        expect(refreshedInvoked).to.be.equal(false, 'Refreshed invoked');
+
+        locatingDeferred3.resolve();
+
+        await sleep(10);
+        expect(refreshedInvoked).to.be.equal(true, 'Refreshed not invoked');
+    });
+});