chore: use for..of instead of forEach (#14517)

Author: SimenB

.eslintrc.cjs

@@ -595,6 +595,7 @@ module.exports = {
     yoda: 'off',
 
     'unicorn/explicit-length-check': 'error',
+    'unicorn/no-array-for-each': 'error',
     'unicorn/no-negated-condition': 'error',
     'unicorn/prefer-default-parameters': 'error',
     'unicorn/prefer-includes': 'error',

e2e/MockStdinWatchPlugin.js

@@ -20,7 +20,7 @@ class MockStdinWatchPlugin {
   apply(jestHooks) {
     jestHooks.onTestRunComplete(() => {
       const {keys} = this._config.input.shift();
-      keys.forEach(key => this._stdin.emit('data', key));
+      for (const key of keys) this._stdin.emit('data', key);
     });
   }
 }

e2e/Utils.ts

@@ -128,7 +128,7 @@ export const writeFiles = (
   files: {[filename: string]: string},
 ) => {
   fs.mkdirSync(directory, {recursive: true});
-  Object.keys(files).forEach(fileOrPath => {
+  for (const fileOrPath of Object.keys(files)) {
     const dirname = path.dirname(fileOrPath);
 
     if (dirname !== '/') {
@@ -138,15 +138,15 @@ export const writeFiles = (
       path.resolve(directory, ...fileOrPath.split('/')),
       dedent(files[fileOrPath]),
     );
-  });
+  }
 };
 
 export const writeSymlinks = (
   directory: string,
   symlinks: {[existingFile: string]: string},
 ) => {
   fs.mkdirSync(directory, {recursive: true});
-  Object.keys(symlinks).forEach(fileOrPath => {
+  for (const fileOrPath of Object.keys(symlinks)) {
     const symLinkPath = symlinks[fileOrPath];
     const dirname = path.dirname(symLinkPath);
 
@@ -158,7 +158,7 @@ export const writeSymlinks = (
       path.resolve(directory, ...symLinkPath.split('/')),
       'junction',
     );
-  });
+  }
 };
 
 const NUMBER_OF_TESTS_TO_FORCE_USING_WORKERS = 25;

e2e/__tests__/coverageRemapping.test.ts

@@ -27,11 +27,11 @@ it('maps code coverage against original source', () => {
   const coverageMap = JSON.parse(readFileSync(coverageMapFile, 'utf-8'));
 
   // reduce absolute paths embedded in the coverage map to just filenames
-  Object.keys(coverageMap).forEach(filename => {
+  for (const filename of Object.keys(coverageMap)) {
     coverageMap[filename].path = path.basename(coverageMap[filename].path);
     delete coverageMap[filename].hash;
     coverageMap[path.basename(filename)] = coverageMap[filename];
     delete coverageMap[filename];
-  });
+  }
   expect(coverageMap).toMatchSnapshot();
 });

e2e/__tests__/coverageTransformInstrumented.test.ts

@@ -27,11 +27,11 @@ it('code coverage for transform instrumented code', () => {
   const coverageMap = JSON.parse(readFileSync(coverageMapFile, 'utf-8'));
 
   // reduce absolute paths embedded in the coverage map to just filenames
-  Object.keys(coverageMap).forEach(filename => {
+  for (const filename of Object.keys(coverageMap)) {
     coverageMap[filename].path = path.basename(coverageMap[filename].path);
     delete coverageMap[filename].hash;
     coverageMap[path.basename(filename)] = coverageMap[filename];
     delete coverageMap[filename];
-  });
+  }
   expect(coverageMap).toMatchSnapshot();
 });

e2e/__tests__/errorOnDeprecated.test.ts

@@ -31,7 +31,7 @@ const SHOULD_NOT_PASS_IN_JEST = new Set([
   'spyOnProperty.test.js',
 ]);
 
-testFiles.forEach(testFile => {
+for (const testFile of testFiles) {
   test(`${testFile} errors in errorOnDeprecated mode`, () => {
     const result = runJest('error-on-deprecated', [
       testFile,
@@ -42,9 +42,9 @@ testFiles.forEach(testFile => {
 
     expect(rest).toMatchSnapshot();
   });
-});
+}
 
-testFiles.forEach(testFile => {
+for (const testFile of testFiles) {
   const shouldPass = SHOULD_NOT_PASS_IN_JEST.has(testFile);
 
   const expectation = `${testFile} ${shouldPass ? 'errors' : 'passes'}`;
@@ -54,4 +54,4 @@ testFiles.forEach(testFile => {
     const result = runJest('error-on-deprecated', [testFile]);
     expect(result.exitCode).toBe(shouldPass ? 1 : 0);
   });
-});
+}

e2e/__tests__/snapshot.test.ts

@@ -70,19 +70,19 @@ const getSnapshotOfCopy = () => {
 
 describe('Snapshot', () => {
   const cleanup = () => {
-    [
+    for (const file of [
       snapshotFile,
       secondSnapshotFile,
       snapshotOfCopy,
       copyOfTestPath,
       snapshotEscapeFile,
       snapshotEscapeRegexFile,
       snapshotEscapeSubstitutionFile,
-    ].forEach(file => {
+    ]) {
       if (fileExists(file)) {
         fs.unlinkSync(file);
       }
-    });
+    }
     if (fileExists(snapshotDir)) {
       fs.rmdirSync(snapshotDir);
     }

e2e/__tests__/summaryThreshold.test.ts

@@ -7,7 +7,7 @@
 
 import runJest from '../runJest';
 
-['default', 'summary'].forEach(reporter => {
+for (const reporter of ['default', 'summary']) {
   describe(`${reporter} reporter`, () => {
     test('prints failure messages when total number of test suites is over summaryThreshold', () => {
       const {exitCode, stderr} = runJest('summary-threshold', [
@@ -26,4 +26,4 @@ import runJest from '../runJest';
       );
     });
   });
-});
+}

e2e/__tests__/transform.test.ts

@@ -199,9 +199,9 @@ describe('transformer caching', () => {
     const loggedFiles = stdout.split('\n');
 
     // Verify any lines logged are _just_ the file we care about
-    loggedFiles.forEach(line => {
+    for (const line of loggedFiles) {
       expect(line).toBe(transformedFile);
-    });
+    }
 
     // We run with 2 workers, so the file should be transformed twice
     expect(loggedFiles).toHaveLength(2);

e2e/__tests__/watchModeOnlyFailed.test.ts

@@ -41,9 +41,9 @@ test('can press "f" to run only failed tests', () => {
   const results = extractSummaries(stderr);
 
   expect(results).toHaveLength(2);
-  results.forEach(({rest, summary}) => {
+  for (const {rest, summary} of results) {
     expect(rest).toMatchSnapshot('test results');
     expect(summary).toMatchSnapshot('test summary');
-  });
+  }
   expect(exitCode).toBe(0);
 });