Fix coverage reporter for uncovered files without transformers

CHANGELOG.md

@@ -6,7 +6,8 @@
 
 ### Fixes
 
-- `[jest-circus]` Fix type ellision of jest-runtime imports ([#9717](https://github.com/facebook/jest/pull/9717))
+- `[jest-circus]` Fix type elision of jest-runtime imports ([#9717](https://github.com/facebook/jest/pull/9717))
+- `[@jest/transform]` Fix coverage reporter for uncovered files without transformers, reverting ([#9460](https://github.com/facebook/jest/pull/9460)) ([#9724](https://github.com/facebook/jest/pull/9724))
 
 ### Chore & Maintenance
 

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

@@ -0,0 +1,10 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`produces code coverage for uncovered files without transformer 1`] = `
+---------------------|---------|----------|---------|---------|-------------------
+File                 | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
+---------------------|---------|----------|---------|---------|-------------------
+All files            |       0 |      100 |       0 |       0 |                   
+ some-random-file.js |       0 |      100 |       0 |       0 | 8,10,11           
+---------------------|---------|----------|---------|---------|-------------------
+`;

e2e/__tests__/coverageWithoutTransform.test.ts

@@ -0,0 +1,29 @@
+/**
+ * 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 {wrap} from 'jest-snapshot-serializer-raw';
+import {cleanup} from '../Utils';
+import runJest from '../runJest';
+
+const dir = path.resolve(__dirname, '../coverage-without-transform');
+const coverageDir = path.join(dir, 'coverage');
+
+beforeAll(() => {
+  cleanup(coverageDir);
+});
+
+afterAll(() => {
+  cleanup(coverageDir);
+});
+
+it('produces code coverage for uncovered files without transformer', () => {
+  const {exitCode, stdout} = runJest(dir, ['--coverage', '--no-cache']);
+
+  expect(exitCode).toBe(0);
+  expect(wrap(stdout)).toMatchSnapshot();
+});

e2e/coverage-without-transform/__tests__/test.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.
+ */
+
+it('dummy test', () => {
+  expect(1).toBe(1);
+});

e2e/coverage-without-transform/package.json

@@ -0,0 +1,7 @@
+{
+  "jest": {
+    "collectCoverageFrom": ["*.js"],
+    "transform": {},
+    "testEnvironment": "node"
+  }
+}

e2e/coverage-without-transform/some-random-file.js

@@ -0,0 +1,12 @@
+/**
+ * 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 = function doES6Stuff(testObj, multiplier) {
+  // eslint-disable-next-line no-unused-vars
+  const {someNumber, ...others} = testObj;
+  return someNumber * multiplier;
+};

packages/jest-transform/src/ScriptTransformer.ts

@@ -191,12 +191,8 @@ export default class ScriptTransformer {
     return transform;
   }
 
-  private _instrumentFile(
-    filename: Config.Path,
-    input: TransformedSource,
-    canMapToInput: boolean,
-  ): TransformedSource {
-    const result = babelTransform(input.code, {
+  private _instrumentFile(filename: Config.Path, content: string): string {
+    const result = babelTransform(content, {
       auxiliaryCommentBefore: ' istanbul ignore next ',
       babelrc: false,
       caller: {
@@ -214,27 +210,21 @@ export default class ScriptTransformer {
             cwd: this._config.rootDir,
             exclude: [],
             extension: false,
-            // Needed for correct coverage as soon as we start storing a source map of the instrumented code
-            inputSourceMap: input.map,
             useInlineSourceMaps: false,
           },
         ],
       ],
-      /**
-       * It's necessary to be able to map back to original source from the instrumented code.
-       * The inline map is needed for debugging functionality, and exposing it as a separate file is needed
-       * for mapping stack traces. It's convenient to use 'both' here and avoid extracting the source map.
-       *
-       * Previous behavior of emitting no map when we can't map back to original source is preserved.
-       */
-      sourceMaps: canMapToInput ? 'both' : false,
     });
 
-    if (result && result.code) {
-      return result as TransformResult;
+    if (result) {
+      const {code} = result;
+
+      if (code) {
+        return code;
+      }
     }
 
-    return {code: input.code};
+    return content;
   }
 
   private _getRealPath(filepath: Config.Path): Config.Path {
@@ -328,36 +318,17 @@ export default class ScriptTransformer {
       }
     }
 
-    // Apply instrumentation to the code if necessary, keeping the instrumented code and new map
-    let map = transformed.map;
     if (!transformWillInstrument && instrument) {
-      /**
-       * We can map the original source code to the instrumented code ONLY if
-       * - the process of transforming the code produced a source map e.g. ts-jest
-       * - we did not transform the source code
-       *
-       * Otherwise we cannot make any statements about how the instrumented code corresponds to the original code,
-       * and we should NOT emit any source maps
-       *
-       */
-      const shouldEmitSourceMaps = (!!transform && !!map) || !transform;
-      const instrumented = this._instrumentFile(
-        filename,
-        transformed,
-        shouldEmitSourceMaps,
-      );
-      code = instrumented.code;
-
-      if (instrumented.map) {
-        map = instrumented.map;
-      }
+      code = this._instrumentFile(filename, transformed.code);
     } else {
       code = transformed.code;
     }
 
-    if (map) {
+    if (transformed.map) {
       const sourceMapContent =
-        typeof map === 'string' ? map : JSON.stringify(map);
+        typeof transformed.map === 'string'
+          ? transformed.map
+          : JSON.stringify(transformed.map);
       writeCacheFile(sourceMapPath, sourceMapContent);
     } else {
       sourceMapPath = null;

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

@@ -78,7 +78,7 @@ exports[`ScriptTransformer transforms a file properly 1`] = `
 /* istanbul ignore next */
 function cov_25u22311x4() {
   var path = "/fruits/banana.js";
-  var hash = "3f8e915bed83285455a8a16aa04dc0cf5242d755";
+  var hash = "4be0f6184160be573fc43f7c2a5877c28b7ce249";
   var global = new Function("return this")();
   var gcv = "__coverage__";
   var coverageData = {
@@ -102,9 +102,8 @@ function cov_25u22311x4() {
     },
     f: {},
     b: {},
-    inputSourceMap: null,
     _coverageSchema: "1a1c01bbd47fc00a2c39e90264f33305004495a9",
-    hash: "3f8e915bed83285455a8a16aa04dc0cf5242d755"
+    hash: "4be0f6184160be573fc43f7c2a5877c28b7ce249"
   };
   var coverage = global[gcv] || (global[gcv] = {});
 
@@ -124,14 +123,13 @@ function cov_25u22311x4() {
 cov_25u22311x4();
 cov_25u22311x4().s[0]++;
 module.exports = "banana";
-//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImJhbmFuYS5qcyJdLCJuYW1lcyI6WyJtb2R1bGUiLCJleHBvcnRzIl0sIm1hcHBpbmdzIjoiOzs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7QUFBQUEsTUFBTSxDQUFDQyxPQUFQLEdBQWlCLFFBQWpCIiwic291cmNlc0NvbnRlbnQiOlsibW9kdWxlLmV4cG9ydHMgPSBcImJhbmFuYVwiOyJdfQ==
 `;
 
 exports[`ScriptTransformer transforms a file properly 2`] = `
 /* istanbul ignore next */
 function cov_23yvu8etmu() {
   var path = "/fruits/kiwi.js";
-  var hash = "8b5afd38d79008f13ebc229b89ef82b12ee9447a";
+  var hash = "7705dd5fcfbc884dcea7062944cfb8cc5d141d1a";
   var global = new Function("return this")();
   var gcv = "__coverage__";
   var coverageData = {
@@ -193,9 +191,8 @@ function cov_23yvu8etmu() {
       "0": 0
     },
     b: {},
-    inputSourceMap: null,
     _coverageSchema: "1a1c01bbd47fc00a2c39e90264f33305004495a9",
-    hash: "8b5afd38d79008f13ebc229b89ef82b12ee9447a"
+    hash: "7705dd5fcfbc884dcea7062944cfb8cc5d141d1a"
   };
   var coverage = global[gcv] || (global[gcv] = {});
 
@@ -221,7 +218,6 @@ module.exports = () => {
   cov_23yvu8etmu().s[1]++;
   return "kiwi";
 };
-//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbImtpd2kuanMiXSwibmFtZXMiOlsibW9kdWxlIiwiZXhwb3J0cyJdLCJtYXBwaW5ncyI6Ijs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7O0FBQUFBLE1BQU0sQ0FBQ0MsT0FBUCxHQUFpQixNQUFNO0FBQUE7QUFBQTtBQUFBO0FBQUE7QUFBTSxDQUE3QiIsInNvdXJjZXNDb250ZW50IjpbIm1vZHVsZS5leHBvcnRzID0gKCkgPT4gXCJraXdpXCI7Il19
 `;
 
 exports[`ScriptTransformer uses multiple preprocessors 1`] = `

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

@@ -535,96 +535,6 @@ describe('ScriptTransformer', () => {
     expect(writeFileAtomic.sync).toHaveBeenCalledTimes(1);
   });
 
-  it('should write a source map for the instrumented file when transformed', () => {
-    const transformerConfig = {
-      ...config,
-      transform: [['^.+\\.js$', 'preprocessor-with-sourcemaps']],
-    };
-    const scriptTransformer = new ScriptTransformer(transformerConfig);
-
-    const map = {
-      mappings: ';AAAA',
-      version: 3,
-    };
-
-    // A map from the original source to the instrumented output
-    /* eslint-disable sort-keys */
-    const instrumentedCodeMap = {
-      version: 3,
-      sources: ['banana.js'],
-      names: ['content'],
-      mappings: ';;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAAA,OAAO',
-      sourcesContent: ['content'],
-    };
-    /* eslint-enable */
-
-    require('preprocessor-with-sourcemaps').process.mockReturnValue({
-      code: 'content',
-      map,
-    });
-
-    const result = scriptTransformer.transform(
-      '/fruits/banana.js',
-      makeGlobalConfig({
-        collectCoverage: true,
-      }),
-    );
-    expect(result.sourceMapPath).toEqual(expect.any(String));
-    expect(writeFileAtomic.sync).toBeCalledTimes(2);
-    expect(writeFileAtomic.sync).toBeCalledWith(
-      result.sourceMapPath,
-      JSON.stringify(instrumentedCodeMap),
-      {
-        encoding: 'utf8',
-        fsync: false,
-      },
-    );
-
-    // Inline source map allows debugging of original source when running instrumented code
-    expect(result.code).toContain('//# sourceMappingURL');
-  });
-
-  it('should write a source map for the instrumented file when not transformed', () => {
-    const scriptTransformer = new ScriptTransformer(config);
-
-    // A map from the original source to the instrumented output
-    /* eslint-disable sort-keys */
-    const instrumentedCodeMap = {
-      version: 3,
-      sources: ['banana.js'],
-      names: ['module', 'exports'],
-      mappings:
-        ';;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;AAAAA,MAAM,CAACC,OAAP,GAAiB,QAAjB',
-      sourcesContent: ['module.exports = "banana";'],
-    };
-    /* eslint-enable */
-
-    require('preprocessor-with-sourcemaps').process.mockReturnValue({
-      code: 'content',
-      map: null,
-    });
-
-    const result = scriptTransformer.transform(
-      '/fruits/banana.js',
-      makeGlobalConfig({
-        collectCoverage: true,
-      }),
-    );
-    expect(result.sourceMapPath).toEqual(expect.any(String));
-    expect(writeFileAtomic.sync).toBeCalledTimes(2);
-    expect(writeFileAtomic.sync).toBeCalledWith(
-      result.sourceMapPath,
-      JSON.stringify(instrumentedCodeMap),
-      {
-        encoding: 'utf8',
-        fsync: false,
-      },
-    );
-
-    // Inline source map allows debugging of original source when running instrumented code
-    expect(result.code).toContain('//# sourceMappingURL');
-  });
-
   it('passes expected transform options to getCacheKey', () => {
     config = {...config, transform: [['^.+\\.js$', 'test_preprocessor']]};
     const scriptTransformer = new ScriptTransformer(config);