build(lint): enable no-array-for-each #6281

## Problem
Many bugs, and confusing behavior stem from developers using an async
function within a forEach. This is almost always not desired.
Additionally, `forEach` can lead to bloated implementations when other
methods like `some`, `find`, `reduce`, or `flatMap` are more applicable.

According to
https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/no-array-for-each.md
It is also faster with `for ... of`.

## Solution
- Add lint rule: https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/no-array-for-each.md
- Migrate existing cases with `eslint CLI --fix` (75% of cases).
- For remaining cases, mark as exception.

Author: Hweinstock

.eslintrc.js

@@ -158,6 +158,8 @@ module.exports = {
         'unicorn/prefer-reflect-apply': 'error',
         'unicorn/prefer-string-trim-start-end': 'error',
         'unicorn/prefer-type-error': 'error',
+        // Discourage `.forEach` because it can lead to accidental, incorrect use of async callbacks.
+        'unicorn/no-array-for-each': 'error',
         'security-node/detect-child-process': 'error',
 
         'header/header': [

packages/amazonq/src/inlineChat/controller/inlineChatController.ts

@@ -156,7 +156,9 @@ export class InlineChatController {
     }
 
     private async reset() {
-        this.listeners.forEach((listener) => listener.dispose())
+        for (const listener of this.listeners) {
+            listener.dispose()
+        }
         this.listeners = []
 
         this.task = undefined

packages/amazonq/src/inlineChat/output/computeDiff.ts

@@ -2,7 +2,7 @@
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
-import { type LinesOptions, diffLines, Change } from 'diff'
+import { type LinesOptions, diffLines } from 'diff'
 import * as vscode from 'vscode'
 import { InlineTask, TextDiff } from '../controller/inlineTask'
 
@@ -24,8 +24,7 @@ export function computeDiff(response: string, inlineTask: InlineTask, isPartialD
 
     const textDiff: TextDiff[] = []
     let startLine = selectedRange.start.line
-
-    diffs.forEach((part: Change) => {
+    for (const part of diffs) {
         const count = part.count ?? 0
         if (part.removed) {
             if (part.value !== '\n') {
@@ -49,7 +48,7 @@ export function computeDiff(response: string, inlineTask: InlineTask, isPartialD
             }
         }
         startLine += count
-    })
+    }
     inlineTask.diff = textDiff
     return textDiff
 }

packages/amazonq/test/e2e/amazonq/explore.test.ts

@@ -36,10 +36,10 @@ describe('Amazon Q Explore page', function () {
     it('should have correct button IDs', async () => {
         const features = ['featuredev', 'testgen', 'doc', 'review', 'gumby']
 
-        features.forEach((feature, index) => {
+        for (const [index, feature] of features.entries()) {
             const buttons = (tab.getStore().chatItems ?? [])[index].buttons ?? []
             assert.deepStrictEqual(buttons[0].id, `user-guide-${feature}`)
             assert.deepStrictEqual(buttons[1].id, `quick-start-${feature}`)
-        })
+        }
     })
 })

packages/amazonq/test/e2e/amazonq/welcome.test.ts

@@ -51,11 +51,11 @@ describe('Amazon Q Welcome page', function () {
             framework.createTab()
 
             let welcomeCount = 0
-            framework.getTabs().forEach((tab) => {
+            for (const tab of framework.getTabs()) {
                 if (tab.getStore().tabTitle === 'Welcome to Q') {
                     welcomeCount++
                 }
-            })
+            }
             // 3 welcome tabs
             assert.deepStrictEqual(welcomeCount, 3)
 

packages/amazonq/test/unit/codewhisperer/service/keyStrokeHandler.test.ts

@@ -212,7 +212,7 @@ describe('keyStrokeHandler', function () {
             ['function suggestedByIntelliSense():', DocumentChangedSource.Unknown],
         ]
 
-        cases.forEach((tuple) => {
+        for (const tuple of cases) {
             const input = tuple[0]
             const expected = tuple[1]
             it(`test input ${input} should return ${expected}`, function () {
@@ -221,7 +221,7 @@ describe('keyStrokeHandler', function () {
                 ).checkChangeSource()
                 assert.strictEqual(actual, expected)
             })
-        })
+        }
 
         function createFakeDocumentChangeEvent(str: string): ReadonlyArray<vscode.TextDocumentContentChangeEvent> {
             return [

packages/amazonq/test/unit/codewhisperer/util/crossFileContextUtil.test.ts

@@ -251,11 +251,11 @@ describe('crossFileContextUtil', function () {
             const actual = await crossFile.getCrossFileCandidates(editor)
 
             assert.ok(actual.length === 5)
-            actual.forEach((actualFile, index) => {
+            for (const [index, actualFile] of actual.entries()) {
                 const expectedFile = path.join(tempFolder, expectedFilePaths[index])
                 assert.strictEqual(normalize(expectedFile), normalize(actualFile))
                 assert.ok(areEqual(tempFolder, actualFile, expectedFile))
-            })
+            }
         })
     })
 
@@ -274,7 +274,7 @@ describe('crossFileContextUtil', function () {
             await closeAllEditors()
         })
 
-        fileExtLists.forEach((fileExt) => {
+        for (const fileExt of fileExtLists) {
             it('should be empty if userGroup is control', async function () {
                 const editor = await toTextEditor('content-1', `file-1.${fileExt}`, tempFolder)
                 await toTextEditor('content-2', `file-2.${fileExt}`, tempFolder, { preview: false })
@@ -287,7 +287,7 @@ describe('crossFileContextUtil', function () {
 
                 assert.ok(actual && actual.supplementalContextItems.length === 0)
             })
-        })
+        }
     })
 
     describe.skip('partial support - crossfile group', function () {
@@ -305,7 +305,7 @@ describe('crossFileContextUtil', function () {
             await closeAllEditors()
         })
 
-        fileExtLists.forEach((fileExt) => {
+        for (const fileExt of fileExtLists) {
             it('should be non empty if usergroup is Crossfile', async function () {
                 const editor = await toTextEditor('content-1', `file-1.${fileExt}`, tempFolder)
                 await toTextEditor('content-2', `file-2.${fileExt}`, tempFolder, { preview: false })
@@ -318,7 +318,7 @@ describe('crossFileContextUtil', function () {
 
                 assert.ok(actual && actual.supplementalContextItems.length !== 0)
             })
-        })
+        }
     })
 
     describe('full support', function () {
@@ -337,7 +337,7 @@ describe('crossFileContextUtil', function () {
             await closeAllEditors()
         })
 
-        fileExtLists.forEach((fileExt) => {
+        for (const fileExt of fileExtLists) {
             it(`supplemental context for file ${fileExt} should be non empty`, async function () {
                 sinon.stub(FeatureConfigProvider.instance, 'getProjectContextGroup').returns('control')
                 sinon
@@ -361,7 +361,7 @@ describe('crossFileContextUtil', function () {
 
                 assert.ok(actual && actual.supplementalContextItems.length !== 0)
             })
-        })
+        }
     })
 
     describe('splitFileToChunks', function () {

packages/amazonq/test/unit/codewhisperer/util/editorContext.test.ts

@@ -95,12 +95,12 @@ describe('editorContext', function () {
                 ['c', 'c'],
             ])
 
-            languageToExtension.forEach((extension, language) => {
+            for (const [language, extension] of languageToExtension.entries()) {
                 const editor = createMockTextEditor('', 'test.ipynb', language, 1, 17)
                 const actual = EditorContext.getFileRelativePath(editor)
                 const expected = 'test.' + extension
                 assert.strictEqual(actual, expected)
-            })
+            }
         })
 
         it('Should return relative path', async function () {

packages/amazonq/test/unit/codewhisperer/util/runtimeLanguageContext.test.ts

@@ -52,15 +52,15 @@ describe('runtimeLanguageContext', function () {
             await resetCodeWhispererGlobalVariables()
         })
 
-        cases.forEach((tuple) => {
+        for (const tuple of cases) {
             const languageId = tuple[0]
             const expected = tuple[1]
 
             it(`should ${expected ? '' : 'not'} support ${languageId}`, function () {
                 const actual = languageContext.isLanguageSupported(languageId)
                 assert.strictEqual(actual, expected)
             })
-        })
+        }
 
         describe('test isLanguageSupported with document as the argument', function () {
             const cases: [string, boolean][] = [
@@ -105,7 +105,7 @@ describe('runtimeLanguageContext', function () {
                 ['helloFoo.foo', false],
             ]
 
-            cases.forEach((tuple) => {
+            for (const tuple of cases) {
                 const fileName = tuple[0]
                 const expected = tuple[1]
 
@@ -114,7 +114,7 @@ describe('runtimeLanguageContext', function () {
                     const actual = languageContext.isLanguageSupported(doc)
                     assert.strictEqual(actual, expected)
                 })
-            })
+            }
         })
     })
 
@@ -148,14 +148,14 @@ describe('runtimeLanguageContext', function () {
             [undefined, 'plaintext'],
         ]
 
-        cases.forEach((tuple) => {
+        for (const tuple of cases) {
             const vscLanguageId = tuple[0]
             const expectedCwsprLanguageId = tuple[1]
             it(`given vscLanguage ${vscLanguageId} should return ${expectedCwsprLanguageId}`, function () {
                 const result = runtimeLanguageContext.getLanguageContext(vscLanguageId)
                 assert.strictEqual(result.language as string, expectedCwsprLanguageId)
             })
-        })
+        }
     })
 
     describe('normalizeLanguage', function () {

packages/amazonq/test/unit/codewhisperer/util/securityScanLanguageContext.test.ts

@@ -51,15 +51,15 @@ describe('securityScanLanguageContext', function () {
             await resetCodeWhispererGlobalVariables()
         })
 
-        cases.forEach((tuple) => {
+        for (const tuple of cases) {
             const languageId = tuple[0]
             const expected = tuple[1]
 
             it(`should ${expected ? '' : 'not'} support ${languageId}`, function () {
                 const actual = languageContext.isLanguageSupported(languageId)
                 assert.strictEqual(actual, expected)
             })
-        })
+        }
     })
 
     describe('normalizeLanguage', function () {