add mapCoverage to CLI, switch off by default

dangerfile.js

@@ -51,7 +51,9 @@ const raiseIssueAboutPaths = (
 };
 
 const newJsFiles = danger.git.created_files.filter(path => path.endsWith('js'));
-const isSourceFile = path => includes(path, '/src/');
+const isSourceFile = path => 
+  includes(path, '/src/') &&
+  !includes(path, '__tests__');
 
 // New JS files should have the FB copyright header + flow
 const facebookLicenseHeaderComponents = [

docs/Configuration.md

@@ -154,14 +154,18 @@ Note that, if you specify a global reference value (like an object or array) her
 
 ##### available in Jest **19.0.0+**
 
-Default: `true`
-
-If you have [transformers](#transform-object-string-string) configured that emit
-source maps, Jest will use them to map code coverage against the original source
-code when writing [reports](#coveragereporters-array-string) and checking
-[thresholds](#coveragethreshold-object). This can be resource-intensive. If Jest
-consumes large amounts of memory while calculating coverage, try setting this
-option to `false`.
+Default: `false`
+
+If you have [transformers](#transform-object-string-string) configured that emit source maps, Jest will use them to map code coverage against the original source code when writing [reports](#coveragereporters-array-string) and checking [thresholds](#coveragethreshold-object). This can be resource-intensive. If Jest is taking a long time to calculate coverage at the end of a test run, try setting this option to `false`.
+
+Both inline source maps and source maps returned directly from a transformer are supported. Source map URLs are not supported because Jest may not be able to locate them. To return source maps from a transformer, the `process` function can return an object like the following. The sourceMap property may either be an object, or a string of JSON.
+
+```js
+return {
+  content: 'the code',
+  sourceMap: 'the source map',
+};
+```
 
 ### `moduleFileExtensions` [array<string>]
 Default: `["js", "json", "jsx", "node"]`

integration_tests/__tests__/__snapshots__/coverage-remapping-test.js.snap

@@ -1,4 +1,4 @@
-exports[`test maps code coverage against original source 1`] = `
+exports[`maps code coverage against original source 1`] = `
 Object {
   "covered.ts": Object {
     "b": Object {

integration_tests/__tests__/coverage-remapping-test.js

@@ -19,7 +19,7 @@ skipOnWindows.suite();
 it('maps code coverage against original source', () => {
   const dir = path.resolve(__dirname, '../coverage-remapping');
   run('npm install', dir);
-  runJest(dir, ['--coverage', '--no-cache']);
+  runJest(dir, ['--coverage', '--mapCoverage', '--no-cache']);
 
   const coverageMapFile = path.join(
     __dirname,

packages/jest-cli/src/cli/args.js

@@ -147,6 +147,12 @@ const options = {
       'leaks. Use together with `--runInBand` and `--expose-gc` in node.',
     type: 'boolean',
   },
+  mapCoverage: {
+    description:
+      'Maps code coverage reports against original source code when ' +
+      'transformers supply source maps.',
+    type: 'boolean',
+  },
   maxWorkers: {
     alias: 'w',
     description:

packages/jest-config/src/defaults.js

@@ -32,7 +32,7 @@ module.exports = ({
   haste: {
     providesModuleNodeModules: [],
   },
-  mapCoverage: true,
+  mapCoverage: false,
   moduleDirectories: ['node_modules'],
   moduleFileExtensions: [
     'js',

packages/jest-config/src/setFromArgv.js

@@ -13,6 +13,10 @@ function setFromArgv(config, argv) {
     config.collectCoverage = true;
   }
 
+  if (argv.mapCoverage) {
+    config.mapCoverage = true;
+  }
+
   if (argv.verbose) {
     config.verbose = argv.verbose;
   }

packages/jest-config/src/validConfig.js

@@ -45,7 +45,7 @@ module.exports = ({
   },
   logHeapUsage: true,
   logTransformErrors: true,
-  mapCoverage: true,
+  mapCoverage: false,
   moduleDirectories: ['node_modules'],
   moduleFileExtensions: ['js', 'json', 'jsx', 'node'],
   moduleLoader: '<rootDir>',

packages/jest-runtime/src/__tests__/__snapshots__/transform-test.js.snap

@@ -4,7 +4,15 @@ exports[`transform does not instrument with source map if mapCoverage config opt
 `;
 
 exports[`transform instruments with source map if preprocessor inlines it 1`] = `
-"({\\"Object.<anonymous>\\":function(module,exports,require,__dirname,__filename,global,jest){/* istanbul ignore next */var cov_25u22311x4 = function () {var path = \\"/fruits/banana.js\\",hash = \\"5dc8e485e00fed337d9101d8fac0e5dd5a88b834\\",global = new Function('return this')(),gcv = \\"__coverage__\\",coverageData = { path: \\"/fruits/banana.js\\", statementMap: { \\"0\\": { start: { line: 1, column: 12 }, end: { line: 1, column: 24 } } }, fnMap: {}, branchMap: { \\"0\\": { loc: { start: { line: 1, column: 12 }, end: { line: 1, column: 24 } }, type: \\"cond-expr\\", locations: [{ start: { line: 1, column: 19 }, end: { line: 1, column: 20 } }, { start: { line: 1, column: 23 }, end: { line: 1, column: 24 } }] } }, s: { \\"0\\": 0 }, f: {}, b: { \\"0\\": [0, 0] }, _coverageSchema: \\"332fd63041d2c1bcb487cc26dd0d5f7d97098a6c\\" },coverage = global[gcv] || (global[gcv] = {});if (coverage[path] && coverage[path].hash === hash) {return coverage[path];}coverageData.hash = hash;return coverage[path] = coverageData;}();var value = /* istanbul ignore next */(++cov_25u22311x4.s[0], true ? /* istanbul ignore next */(++cov_25u22311x4.b[0][0], 1) : /* istanbul ignore next */(++cov_25u22311x4.b[0][1], 0));
+"({\\"Object.<anonymous>\\":function(module,exports,require,__dirname,__filename,global,jest){/**
+ * Copyright (c) 2016-present, Facebook, Inc. All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict'; /* istanbul ignore next */var cov_25u22311x4 = function () {var path = '/fruits/banana.js',hash = '0f286c0a1633c0df1abca7c94242aff8823cbbc3',global = new Function('return this')(),gcv = '__coverage__',coverageData = { path: '/fruits/banana.js', statementMap: { '0': { start: { line: 9, column: 12 }, end: { line: 9, column: 24 } } }, fnMap: {}, branchMap: { '0': { loc: { start: { line: 9, column: 12 }, end: { line: 9, column: 24 } }, type: 'cond-expr', locations: [{ start: { line: 9, column: 19 }, end: { line: 9, column: 20 } }, { start: { line: 9, column: 23 }, end: { line: 9, column: 24 } }] } }, s: { '0': 0 }, f: {}, b: { '0': [0, 0] }, _coverageSchema: '332fd63041d2c1bcb487cc26dd0d5f7d97098a6c' },coverage = global[gcv] || (global[gcv] = {});if (coverage[path] && coverage[path].hash === hash) {return coverage[path];}coverageData.hash = hash;return coverage[path] = coverageData;}();
+var value = /* istanbul ignore next */(++cov_25u22311x4.s[0], true ? /* istanbul ignore next */(++cov_25u22311x4.b[0][0], 1) : /* istanbul ignore next */(++cov_25u22311x4.b[0][1], 0));
 ;global.__coverage__['/fruits/banana.js'].inputSourceMapPath = '/cache/jest-transform-cache-test/ab/banana_ab.map';
 }});"
 `;

packages/jest-runtime/src/__tests__/transform-test.js

@@ -230,6 +230,10 @@ describe('transform', () => {
   });
 
   it('instruments with source map if preprocessor supplies it', () => {
+    if (skipOnWindows.test()) { //snapshot has file paths
+      return;
+    }
+
     config = Object.assign(config, {
       collectCoverage: true,
       mapCoverage: true,
@@ -256,6 +260,10 @@ describe('transform', () => {
   });
 
   it('instruments with source map if preprocessor inlines it', () => {
+    if (skipOnWindows.test()) { //snapshot has file paths
+      return;
+    }
+
     const realFS = require('fs');
 
     config = Object.assign(config, {