From 6f7934054c21388b8f14ba07a558632f3455a2df Mon Sep 17 00:00:00 2001
From: Endel Dreyer <endel.dreyer@gmail.com>
Date: Tue, 26 Feb 2019 11:49:11 -0300
Subject: [PATCH 1/2] implement Array.prototype.findIndex. closes #456

---
 src/LuaLib.ts                   |  1 +
 src/LuaTransformer.ts           |  2 ++
 src/lualib/ArrayFindIndex.ts    | 17 +++++++++++++++++
 test/unit/lualib/lualib.spec.ts | 17 +++++++++++++++++
 4 files changed, 37 insertions(+)
 create mode 100644 src/lualib/ArrayFindIndex.ts

diff --git a/src/LuaLib.ts b/src/LuaLib.ts
index 864d438f6..3db60196c 100644
--- a/src/LuaLib.ts
+++ b/src/LuaLib.ts
@@ -6,6 +6,7 @@ export enum LuaLibFeature {
     ArrayEvery = "ArrayEvery",
     ArrayFilter = "ArrayFilter",
     ArrayForEach = "ArrayForEach",
+    ArrayFindIndex = "ArrayFindIndex",
     ArrayIndexOf = "ArrayIndexOf",
     ArrayMap = "ArrayMap",
     ArrayPush = "ArrayPush",
diff --git a/src/LuaTransformer.ts b/src/LuaTransformer.ts
index 7d7420ca6..238289a07 100644
--- a/src/LuaTransformer.ts
+++ b/src/LuaTransformer.ts
@@ -3724,6 +3724,8 @@ export class LuaTransformer {
                 );
             case "forEach":
                 return this.transformLuaLibFunction(LuaLibFeature.ArrayForEach, node, caller, ...params);
+            case "findIndex":
+                return this.transformLuaLibFunction(LuaLibFeature.ArrayFindIndex, node, caller, ...params);
             case "indexOf":
                 return this.transformLuaLibFunction(LuaLibFeature.ArrayIndexOf, node, caller, ...params);
             case "map":
diff --git a/src/lualib/ArrayFindIndex.ts b/src/lualib/ArrayFindIndex.ts
new file mode 100644
index 000000000..82866c251
--- /dev/null
+++ b/src/lualib/ArrayFindIndex.ts
@@ -0,0 +1,17 @@
+function __TS__ArrayFindIndex<T>(
+    arr: T[],
+    callbackFn: (this: void, element: T, index?: number, array?: T[]) => boolean
+): number {
+    const len = arr.length;
+    if (len === 0) {
+        return -1;
+    }
+
+    for (let i = 0; i < len; i++) {
+        if (callbackFn(arr[i], i, arr)) {
+            return i;
+        }
+    }
+
+    return -1;
+}
diff --git a/test/unit/lualib/lualib.spec.ts b/test/unit/lualib/lualib.spec.ts
index be87d1084..3c666c2dc 100644
--- a/test/unit/lualib/lualib.spec.ts
+++ b/test/unit/lualib/lualib.spec.ts
@@ -21,6 +21,23 @@ export class LuaLibTests
         Expect(result).toBe(JSON.stringify(expected));
     }
 
+    @TestCase([0, 2, 4, 8], 10, -1)
+    @TestCase([0, 2, 4, 8], 4, 2)
+    @TestCase([0, 2, 4, 8], 8, 3)
+    @Test("findIndex")
+    public findIndex(inp: number[], searchEl: number, expected: number): void
+    {
+        const result = util.transpileAndExecute(
+            `let arrTest = ${JSON.stringify(inp)};
+            return JSONStringify(arrTest.findIndex((elem, index) => {
+                return elem === ${searchEl};
+            }));`
+        );
+
+        // Assert
+        Expect(result).toBe(expected);
+    }
+
     @TestCase([], "x => x")
     @TestCase([0, 1, 2, 3], "x => x")
     @TestCase([0, 1, 2, 3], "x => x*2")

From 858b8435ecd2886f6857e3fb9703e472c425fcf1 Mon Sep 17 00:00:00 2001
From: Endel Dreyer <endel.dreyer@gmail.com>
Date: Tue, 26 Feb 2019 12:23:24 -0300
Subject: [PATCH 2/2] refactor findIndex method, add more test cases

---
 src/lualib/ArrayFindIndex.ts    |  8 +-------
 test/unit/lualib/lualib.spec.ts | 22 +++++++++++++++++++---
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/lualib/ArrayFindIndex.ts b/src/lualib/ArrayFindIndex.ts
index 82866c251..b60190c09 100644
--- a/src/lualib/ArrayFindIndex.ts
+++ b/src/lualib/ArrayFindIndex.ts
@@ -2,16 +2,10 @@ function __TS__ArrayFindIndex<T>(
     arr: T[],
     callbackFn: (this: void, element: T, index?: number, array?: T[]) => boolean
 ): number {
-    const len = arr.length;
-    if (len === 0) {
-        return -1;
-    }
-
-    for (let i = 0; i < len; i++) {
+    for (let i = 0, len = arr.length; i < len; i++) {
         if (callbackFn(arr[i], i, arr)) {
             return i;
         }
     }
-
     return -1;
 }
diff --git a/test/unit/lualib/lualib.spec.ts b/test/unit/lualib/lualib.spec.ts
index 3c666c2dc..83b98aba2 100644
--- a/test/unit/lualib/lualib.spec.ts
+++ b/test/unit/lualib/lualib.spec.ts
@@ -21,11 +21,11 @@ export class LuaLibTests
         Expect(result).toBe(JSON.stringify(expected));
     }
 
+    @TestCase([], 3, -1)
     @TestCase([0, 2, 4, 8], 10, -1)
-    @TestCase([0, 2, 4, 8], 4, 2)
     @TestCase([0, 2, 4, 8], 8, 3)
-    @Test("findIndex")
-    public findIndex(inp: number[], searchEl: number, expected: number): void
+    @Test("array.findIndex[value]")
+    public findIndexByValue(inp: number[], searchEl: number, expected: number): void
     {
         const result = util.transpileAndExecute(
             `let arrTest = ${JSON.stringify(inp)};
@@ -38,6 +38,22 @@ export class LuaLibTests
         Expect(result).toBe(expected);
     }
 
+    @TestCase([0, 2, 4, 8], 3, 8)
+    @TestCase([0, 2, 4, 8], 1, 2)
+    @Test("array.findIndex[index]")
+    public findIndexByIndex(inp: number[], expected: number, value: number): void
+    {
+        const result = util.transpileAndExecute(
+            `let arrTest = ${JSON.stringify(inp)};
+            return JSONStringify(arrTest.findIndex((elem, index, arr) => {
+                return index === ${expected} && arr[${expected}] === ${value};
+            }));`
+        );
+
+        // Assert
+        Expect(result).toBe(expected);
+    }
+
     @TestCase([], "x => x")
     @TestCase([0, 1, 2, 3], "x => x")
     @TestCase([0, 1, 2, 3], "x => x*2")