fix(jest-runtime): correctly report V8 coverage with resetModules: true

CHANGELOG.md

@@ -11,6 +11,7 @@
 - `[@jest/expect-utils]` Fix deep equality of ImmutableJS OrderedMaps ([#12763](https://github.com/facebook/jest/pull/12899))
 - `[jest-docblock]` Handle multiline comments in parseWithComments ([#12845](https://github.com/facebook/jest/pull/12845))
 - `[jest-mock]` Improve `spyOn` error messages ([#12901](https://github.com/facebook/jest/pull/12901))
+- `[jest-runtime]` Correctly report V8 coverage with `resetModules: true` ([#12912](https://github.com/facebook/jest/pull/12912))
 - `[jest-worker]` Make `JestWorkerFarm` helper type to include methods of worker module that take more than one argument ([#12839](https://github.com/facebook/jest/pull/12839))
 
 ### Chore & Maintenance

e2e/__tests__/__snapshots__/coverageProviderV8.test.ts.snap

@@ -85,3 +85,23 @@ All files |     100 |      100 |     100 |     100 |
  x.css    |     100 |      100 |     100 |     100 |                   
 ----------|---------|----------|---------|---------|-------------------"
 `;
+
+exports[`reports coverage with \`resetModules\` 1`] = `
+"  console.log
+    this will print
+
+      at log (module.js:11:11)
+
+  console.log
+    this will print
+
+      at log (module.js:11:11)
+
+--------------|---------|----------|---------|---------|-------------------
+File          | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+--------------|---------|----------|---------|---------|-------------------
+All files     |   59.37 |    33.33 |   33.33 |   59.37 |                   
+ module.js    |   79.16 |       50 |      50 |   79.16 | 14-16,19-20       
+ uncovered.js |       0 |        0 |       0 |       0 | 1-8               
+--------------|---------|----------|---------|---------|-------------------"
+`;

e2e/__tests__/coverageProviderV8.test.ts

@@ -37,6 +37,19 @@ test('prints coverage with empty sourcemaps', () => {
   expect(stdout).toMatchSnapshot();
 });
 
+test('reports coverage with `resetModules`', () => {
+  const sourcemapDir = path.join(DIR, 'with-resetModules');
+
+  const {stdout, exitCode} = runJest(
+    sourcemapDir,
+    ['--coverage', '--coverage-provider', 'v8'],
+    {stripAnsi: true},
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stdout).toMatchSnapshot();
+});
+
 test('prints correct coverage report, if a CJS module is put under test without transformation', () => {
   const sourcemapDir = path.join(DIR, 'cjs-native-without-sourcemap');
 

e2e/coverage-provider-v8/with-resetModules/__tests__/test.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+test('dummy', () => {
+  const {value} = require('../module');
+  expect(value).toBe('abc');
+});
+
+test('reset dummy', () => {
+  const {value} = require('../module');
+  expect(value).toBe('abc');
+});

e2e/coverage-provider-v8/with-resetModules/module.js

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+const value = 'abc';
+
+function covered() {
+  console.log('this will print');
+}
+
+function uncovered() {
+  console.log('this will not');
+}
+
+if (value !== 'abc') {
+  uncovered();
+}
+
+covered();
+
+module.exports = {value};

e2e/coverage-provider-v8/with-resetModules/package.json

@@ -0,0 +1,8 @@
+{
+  "jest": {
+    "collectCoverageFrom": [
+      "*.js"
+    ],
+    "resetModules": true
+  }
+}

e2e/coverage-provider-v8/with-resetModules/uncovered.js

@@ -0,0 +1,8 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+module.exports = {};

packages/jest-runtime/src/index.ts

@@ -221,6 +221,7 @@ export default class Runtime {
   private readonly _fileTransformsMutex: Map<string, Promise<void>>;
   private _v8CoverageInstrumenter: CoverageInstrumenter | undefined;
   private _v8CoverageResult: V8Coverage | undefined;
+  private _v8CoverageSources: Map<string, RuntimeTransformResult> | undefined;
   private readonly _transitiveShouldMock: Map<string, boolean>;
   private _unmockList: RegExp | undefined;
   private readonly _virtualMocks: Map<string, boolean>;
@@ -1155,6 +1156,18 @@ export default class Runtime {
     this._cjsNamedExports.clear();
     this._moduleMockRegistry.clear();
     this._cacheFS.clear();
+
+    if (
+      this._coverageOptions.collectCoverage &&
+      this._coverageOptions.coverageProvider === 'v8' &&
+      this._v8CoverageSources
+    ) {
+      this._v8CoverageSources = new Map([
+        ...this._v8CoverageSources,
+        ...this._fileTransforms,
+      ]);
+    }
+
     this._fileTransforms.clear();
 
     if (this._environment) {
@@ -1182,25 +1195,30 @@ export default class Runtime {
 
   async collectV8Coverage(): Promise<void> {
     this._v8CoverageInstrumenter = new CoverageInstrumenter();
+    this._v8CoverageSources = new Map();
 
     await this._v8CoverageInstrumenter.startInstrumenting();
   }
 
   async stopCollectingV8Coverage(): Promise<void> {
-    if (!this._v8CoverageInstrumenter) {
+    if (!this._v8CoverageInstrumenter || !this._v8CoverageSources) {
       throw new Error('You need to call `collectV8Coverage` first.');
     }
     this._v8CoverageResult =
       await this._v8CoverageInstrumenter.stopInstrumenting();
+    this._v8CoverageSources = new Map([
+      ...this._v8CoverageSources,
+      ...this._fileTransforms,
+    ]);
   }
 
   getAllCoverageInfoCopy(): JestEnvironment['global']['__coverage__'] {
     return deepCyclicCopy(this._environment.global.__coverage__);
   }
 
   getAllV8CoverageInfoCopy(): V8CoverageResult {
-    if (!this._v8CoverageResult) {
-      throw new Error('You need to `stopCollectingV8Coverage` first');
+    if (!this._v8CoverageResult || !this._v8CoverageSources) {
+      throw new Error('You need to call `stopCollectingV8Coverage` first.');
     }
 
     return this._v8CoverageResult
@@ -1210,11 +1228,11 @@ export default class Runtime {
         res =>
           // TODO: will this work on windows? It might be better if `shouldInstrument` deals with it anyways
           res.url.startsWith(this._config.rootDir) &&
-          this._fileTransforms.has(res.url) &&
+          this._v8CoverageSources!.has(res.url) &&
           shouldInstrument(res.url, this._coverageOptions, this._config),
       )
       .map(result => {
-        const transformedFile = this._fileTransforms.get(result.url);
+        const transformedFile = this._v8CoverageSources!.get(result.url);
 
         return {
           codeTransformResult: transformedFile,
@@ -1307,6 +1325,7 @@ export default class Runtime {
     this._fileTransformsMutex.clear();
     this.jestObjectCaches.clear();
 
+    this._v8CoverageSources?.clear();
     this._v8CoverageResult = [];
     this._v8CoverageInstrumenter = undefined;
     this._moduleImplementation = undefined;