Do not elide any imports or exports in preserve-exact

microsoft · andrewbranch · Sep 8, 2021 · May 7, 2021 · May 7, 2021 · May 7, 2021
commit a755070e45a5aef610d03f452e7c8e34395fc131
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
@@ -46,6 +46,7 @@ namespace ts {
         const strictNullChecks = getStrictOptionValue(compilerOptions, "strictNullChecks");
         const languageVersion = getEmitScriptTarget(compilerOptions);
         const moduleKind = getEmitModuleKind(compilerOptions);
+        const { importsNotUsedAsValues } = compilerOptions;
 
         // Save the previous transformation hooks.
         const previousOnEmitNode = context.onEmitNode;
@@ -2802,7 +2803,7 @@ namespace ts {
         }
 
         /**
-         * Visits an import declaration, eliding it if it is not referenced and `importsNotUsedAsValues` is not 'preserve'.
+         * Visits an import declaration, eliding it if it is not referenced and `importsNotUsedAsValues` is not 'preserve' or 'preserve-exact'.
          *
          * @param node The import declaration node.
          */
@@ -2820,8 +2821,9 @@ namespace ts {
             // Elide the declaration if the import clause was elided.
             const importClause = visitNode(node.importClause, visitImportClause, isImportClause);
             return importClause ||
-                compilerOptions.importsNotUsedAsValues === ImportsNotUsedAsValues.Preserve ||
-                compilerOptions.importsNotUsedAsValues === ImportsNotUsedAsValues.Error
+                importsNotUsedAsValues === ImportsNotUsedAsValues.Preserve ||
+                importsNotUsedAsValues === ImportsNotUsedAsValues.PreserveExact ||
+                importsNotUsedAsValues === ImportsNotUsedAsValues.Error
                 ? factory.updateImportDeclaration(
                     node,
                     /*decorators*/ undefined,
@@ -2832,13 +2834,14 @@ namespace ts {
         }
 
         /**
-         * Visits an import clause, eliding it if it is not referenced.
+         * Visits an import clause, eliding it if it is not referenced and `importsNotUsedAsValues` is not 'preserve-exact'.
          *
          * @param node The import clause node.
          */
         function visitImportClause(node: ImportClause): VisitResult<ImportClause> {
-            if (node.isTypeOnly) {
-                return undefined;
+            Debug.assert(!node.isTypeOnly);
+            if (importsNotUsedAsValues === ImportsNotUsedAsValues.PreserveExact) {
+                return node;
             }
             // Elide the import clause if we elide both its name and its named bindings.
             const name = resolver.isReferencedAliasDeclaration(node) ? node.name : undefined;
@@ -2888,7 +2891,7 @@ namespace ts {
 
         /**
          * Visits an export declaration, eliding it if it does not contain a clause that resolves
-         * to a value.
+         * to a value and if `importsNotUsedAsValues` is not 'preserve-exact'.
          *
          * @param node The export declaration node.
          */
@@ -2897,7 +2900,7 @@ namespace ts {
                 return undefined;
             }
 
-            if (!node.exportClause || isNamespaceExport(node.exportClause)) {
+            if (!node.exportClause || isNamespaceExport(node.exportClause) || importsNotUsedAsValues === ImportsNotUsedAsValues.PreserveExact) {
                 // never elide `export <whatever> from <whereever>` declarations -
                 // they should be kept for sideffects/untyped exports, even when the
                 // type checker doesn't know about any exports
@@ -2980,7 +2983,7 @@ namespace ts {
             if (isExternalModuleImportEqualsDeclaration(node)) {
                 const isReferenced = resolver.isReferencedAliasDeclaration(node);
                 // If the alias is unreferenced but we want to keep the import, replace with 'import "mod"'.
-                if (!isReferenced && compilerOptions.importsNotUsedAsValues === ImportsNotUsedAsValues.Preserve) {
+                if (!isReferenced && importsNotUsedAsValues === ImportsNotUsedAsValues.Preserve) {
                     return setOriginalNode(
                         setTextRange(
                             factory.createImportDeclaration(

diff --git a/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.errors.txt b/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.errors.txt
@@ -0,0 +1,35 @@
+tests/cases/conformance/externalModules/typeOnly/d.ts(1,1): error TS1203: Export assignment cannot be used when targeting ECMAScript modules. Consider using 'export default' or another module format instead.
+tests/cases/conformance/externalModules/typeOnly/e.ts(1,1): error TS1202: Import assignment cannot be used when targeting ECMAScript modules. Consider using 'import * as ns from "mod"', 'import {a} from "mod"', 'import d from "mod"', or another module format instead.
+tests/cases/conformance/externalModules/typeOnly/e.ts(2,1): error TS1202: Import assignment cannot be used when targeting ECMAScript modules. Consider using 'import * as ns from "mod"', 'import {a} from "mod"', 'import d from "mod"', or another module format instead.
+
+
+==== tests/cases/conformance/externalModules/typeOnly/a.ts (0 errors) ====
+    export default {};
+    export const b = 0;
+    export const c = 1;
+
+==== tests/cases/conformance/externalModules/typeOnly/b.ts (0 errors) ====
+    import a, { b, c } from "./a";
+
+==== tests/cases/conformance/externalModules/typeOnly/c.ts (0 errors) ====
+    import * as a from "./a";
+
+==== tests/cases/conformance/externalModules/typeOnly/d.ts (1 errors) ====
+    export = {};
+    ~~~~~~~~~~~~
+!!! error TS1203: Export assignment cannot be used when targeting ECMAScript modules. Consider using 'export default' or another module format instead.
+
+==== tests/cases/conformance/externalModules/typeOnly/e.ts (2 errors) ====
+    import D = require("./d");
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS1202: Import assignment cannot be used when targeting ECMAScript modules. Consider using 'import * as ns from "mod"', 'import {a} from "mod"', 'import d from "mod"', or another module format instead.
+    import DD = require("./d");
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS1202: Import assignment cannot be used when targeting ECMAScript modules. Consider using 'import * as ns from "mod"', 'import {a} from "mod"', 'import d from "mod"', or another module format instead.
+    DD;
+
+==== tests/cases/conformance/externalModules/typeOnly/f.ts (0 errors) ====
+    import type a from "./a";
+    import { b, c } from "./a";
+    b;
+
diff --git a/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.js b/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.js
@@ -0,0 +1,43 @@
+//// [tests/cases/conformance/externalModules/typeOnly/importsNotUsedAsValues_preserve-exact.ts] ////
+
+//// [a.ts]
+export default {};
+export const b = 0;
+export const c = 1;
+
+//// [b.ts]
+import a, { b, c } from "./a";
+
+//// [c.ts]
+import * as a from "./a";
+
+//// [d.ts]
+export = {};
+
+//// [e.ts]
+import D = require("./d");
+import DD = require("./d");
+DD;
+
+//// [f.ts]
+import type a from "./a";
+import { b, c } from "./a";
+b;
+
+
+//// [a.js]
+export default {};
+export var b = 0;
+export var c = 1;
+//// [b.js]
+import a, { b, c } from "./a";
+//// [c.js]
+import * as a from "./a";
+//// [d.js]
+export {};
+//// [e.js]
+DD;
+export {};
+//// [f.js]
+import { b, c } from "./a";
+b;
diff --git a/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.symbols b/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.symbols
@@ -0,0 +1,42 @@
+=== tests/cases/conformance/externalModules/typeOnly/a.ts ===
+export default {};
+export const b = 0;
+>b : Symbol(b, Decl(a.ts, 1, 12))
+
+export const c = 1;
+>c : Symbol(c, Decl(a.ts, 2, 12))
+
+=== tests/cases/conformance/externalModules/typeOnly/b.ts ===
+import a, { b, c } from "./a";
+>a : Symbol(a, Decl(b.ts, 0, 6))
+>b : Symbol(b, Decl(b.ts, 0, 11))
+>c : Symbol(c, Decl(b.ts, 0, 14))
+
+=== tests/cases/conformance/externalModules/typeOnly/c.ts ===
+import * as a from "./a";
+>a : Symbol(a, Decl(c.ts, 0, 6))
+
+=== tests/cases/conformance/externalModules/typeOnly/d.ts ===
+export = {};
+No type information for this code.
+No type information for this code.=== tests/cases/conformance/externalModules/typeOnly/e.ts ===
+import D = require("./d");
+>D : Symbol(D, Decl(e.ts, 0, 0))
+
+import DD = require("./d");
+>DD : Symbol(DD, Decl(e.ts, 0, 26))
+
+DD;
+>DD : Symbol(DD, Decl(e.ts, 0, 26))
+
+=== tests/cases/conformance/externalModules/typeOnly/f.ts ===
+import type a from "./a";
+>a : Symbol(a, Decl(f.ts, 0, 6))
+
+import { b, c } from "./a";
+>b : Symbol(b, Decl(f.ts, 1, 8))
+>c : Symbol(c, Decl(f.ts, 1, 11))
+
+b;
+>b : Symbol(b, Decl(f.ts, 1, 8))
+
diff --git a/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.types b/tests/baselines/reference/importsNotUsedAsValues_preserve-exact.types
@@ -0,0 +1,47 @@
+=== tests/cases/conformance/externalModules/typeOnly/a.ts ===
+export default {};
+>{} : {}
+
+export const b = 0;
+>b : 0
+>0 : 0
+
+export const c = 1;
+>c : 1
+>1 : 1
+
+=== tests/cases/conformance/externalModules/typeOnly/b.ts ===
+import a, { b, c } from "./a";
+>a : {}
+>b : 0
+>c : 1
+
+=== tests/cases/conformance/externalModules/typeOnly/c.ts ===
+import * as a from "./a";
+>a : typeof a
+
+=== tests/cases/conformance/externalModules/typeOnly/d.ts ===
+export = {};
+>{} : {}
+
+=== tests/cases/conformance/externalModules/typeOnly/e.ts ===
+import D = require("./d");
+>D : {}
+
+import DD = require("./d");
+>DD : {}
+
+DD;
+>DD : {}
+
+=== tests/cases/conformance/externalModules/typeOnly/f.ts ===
+import type a from "./a";
+>a : any
+
+import { b, c } from "./a";
+>b : 0
+>c : 1
+
+b;
+>b : 0
+
diff --git a/tests/cases/conformance/externalModules/typeOnly/importsNotUsedAsValues_preserve-exact.ts b/tests/cases/conformance/externalModules/typeOnly/importsNotUsedAsValues_preserve-exact.ts
@@ -0,0 +1,26 @@
+// @importsNotUsedAsValues: preserve-exact
+// @module: esnext
+
+// @Filename: a.ts
+export default {};
+export const b = 0;
+export const c = 1;
+
+// @Filename: b.ts
+import a, { b, c } from "./a";
+
+// @Filename: c.ts
+import * as a from "./a";
+
+// @Filename: d.ts
+export = {};
+
+// @Filename: e.ts
+import D = require("./d");
+import DD = require("./d");
+DD;
+
+// @Filename: f.ts
+import type a from "./a";
+import { b, c } from "./a";
+b;