feat: add support for v8 code coverage (#8596)

Author: SimenB

TestUtils.ts

@@ -16,6 +16,7 @@ const DEFAULT_GLOBAL_CONFIG: Config.GlobalConfig = {
   collectCoverageFrom: [],
   collectCoverageOnlyFrom: null,
   coverageDirectory: 'coverage',
+  coverageProvider: 'babel',
   coverageReporters: [],
   coverageThreshold: {global: {}},
   detectLeaks: false,

docs/CLI.md

@@ -152,6 +152,16 @@ Alias: `-c`. The path to a Jest config file specifying how to find and execute t
 
 Alias: `--collectCoverage`. Indicates that test coverage information should be collected and reported in the output. Optionally pass `<boolean>` to override option set in configuration.
 
+### `--coverageProvider=<provider>`
+
+Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default) or `v8`.
+
+Note that using `v8` is considered experimental. This uses V8's builtin code coverage rather than one based on Babel and comes with a few caveats
+
+1. Your node version must include `vm.compileFunction`, which was introduced in [node 10.10](https://nodejs.org/dist/latest-v12.x/docs/api/vm.html#vm_vm_compilefunction_code_params_options)
+1. Tests needs to run in Node test environment (support for `jsdom` is in the works, see [#9315](https://github.com/facebook/jest/issues/9315))
+1. V8 has way better data in the later versions, so using the latest versions of node (v13 at the time of this writing) will yield better results
+
 ### `--debug`
 
 Print debugging info about your Jest config.

docs/Configuration.md

@@ -185,6 +185,16 @@ An array of regexp pattern strings that are matched against all file paths befor
 
 These pattern strings match against the full path. Use the `<rootDir>` string token to include the path to your project's root directory to prevent it from accidentally ignoring all of your files in different environments that may have different root directories. Example: `["<rootDir>/build/", "<rootDir>/node_modules/"]`.
 
+### `coverageProvider` [string]
+
+Indicates which provider should be used to instrument code for coverage. Allowed values are `babel` (default) or `v8`.
+
+Note that using `v8` is considered experimental. This uses V8's builtin code coverage rather than one based on Babel and comes with a few caveats
+
+1. Your node version must include `vm.compileFunction`, which was introduced in [node 10.10](https://nodejs.org/dist/latest-v12.x/docs/api/vm.html#vm_vm_compilefunction_code_params_options)
+1. Tests needs to run in Node test environment (support for `jsdom` is in the works, see [#9315](https://github.com/facebook/jest/issues/9315))
+1. V8 has way better data in the later versions, so using the latest versions of node (v13 at the time of this writing) will yield better results
+
 ### `coverageReporters` [array\<string>]
 
 Default: `["json", "lcov", "text", "clover"]`

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

@@ -84,6 +84,7 @@ exports[`--showConfig outputs config info and exits 1`] = `
     "collectCoverage": false,
     "collectCoverageFrom": [],
     "coverageDirectory": "<<REPLACED_ROOT_DIR>>/coverage",
+    "coverageProvider": "babel",
     "coverageReporters": [
       "json",
       "text",

e2e/__tests__/v8Coverage.test.ts

@@ -0,0 +1,46 @@
+/**
+ * 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.
+ */
+
+import * as path from 'path';
+import {onNodeVersions} from '@jest/test-utils';
+import runJest from '../runJest';
+
+const DIR = path.resolve(__dirname, '../v8-coverage');
+
+onNodeVersions('>=10', () => {
+  test('prints coverage', () => {
+    const sourcemapDir = path.join(DIR, 'no-sourcemap');
+    const {stdout, exitCode} = runJest(
+      sourcemapDir,
+      ['--coverage', '--coverage-provider', 'v8'],
+      {
+        stripAnsi: true,
+      },
+    );
+
+    expect(exitCode).toBe(0);
+    expect(
+      '\n' +
+        stdout
+          .split('\n')
+          .map(s => s.trimRight())
+          .join('\n') +
+        '\n',
+    ).toEqual(`
+  console.log __tests__/Thing.test.js:10
+    42
+
+----------|---------|----------|---------|---------|-------------------
+File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
+----------|---------|----------|---------|---------|-------------------
+All files |     100 |      100 |     100 |     100 |
+ Thing.js |     100 |      100 |     100 |     100 |
+ x.css    |     100 |      100 |     100 |     100 |
+----------|---------|----------|---------|---------|-------------------
+`);
+  });
+});

e2e/v8-coverage/no-sourcemap/Thing.js

@@ -0,0 +1,10 @@
+/**
+ * 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.
+ */
+
+require('./x.css');
+
+module.exports = 42;

e2e/v8-coverage/no-sourcemap/__tests__/Thing.test.js

@@ -0,0 +1,11 @@
+/**
+ * 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 Thing = require('../Thing');
+
+console.log(Thing);
+test.todo('whatever');

e2e/v8-coverage/no-sourcemap/cssTransform.js

@@ -0,0 +1,11 @@
+/**
+ * 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 = {
+  getCacheKey: () => 'cssTransform',
+  process: () => 'module.exports = {};',
+};

e2e/v8-coverage/no-sourcemap/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "no-sourcemap",
+  "version": "1.0.0",
+  "jest": {
+    "testEnvironment": "node",
+    "transform": {
+      "^.+\\.[jt]sx?$": "babel-jest",
+      "^.+\\.css$": "<rootDir>/cssTransform.js"
+    }
+  }
+}