Ignore rootDir to determine the cache key of transformed files in babel-jest

CHANGELOG.md

@@ -7,6 +7,7 @@
 - `[expect]`: Improve report when matcher fails, part 9 ([#7940](https://github.com/facebook/jest/pull/7940))
 - `[pretty-format]` Support `React.memo` ([#7891](https://github.com/facebook/jest/pull/7891))
 - `[jest-config]` Print error information on preset normalization error ([#7935](https://github.com/facebook/jest/pull/7935))
+- `[babel-jest]` Ignore `rootDir` to determine the cache key of transformed files ([#7947](https://github.com/facebook/jest/pull/7947))
 
 ### Fixes
 

e2e/__tests__/__snapshots__/transform.test.js.snap

@@ -6,7 +6,7 @@ FAIL __tests__/ignoredFile.test.js
 
     babel-jest: Babel ignores __tests__/ignoredFile.test.js - make sure to include the file in Jest's transformIgnorePatterns as well.
 
-      at loadBabelConfig (../../../packages/babel-jest/build/index.js:132:13)
+      at loadBabelConfig (../../../packages/babel-jest/build/index.js:142:13)
 `;
 
 exports[`babel-jest instruments only specific files and collects coverage 1`] = `

packages/babel-jest/package.json

@@ -17,6 +17,7 @@
     "babel-plugin-istanbul": "^5.1.0",
     "babel-preset-jest": "^24.1.0",
     "chalk": "^2.4.2",
+    "jest-regex-util": "^24.0.0",
     "slash": "^2.0.0"
   },
   "devDependencies": {

packages/babel-jest/src/__tests__/index.ts

@@ -25,6 +25,10 @@ const mockConfig = {
   moduleFileExtensions: [],
 };
 
+afterEach(() => {
+  jest.unmock('@babel/core');
+});
+
 test(`Returns source string with inline maps when no transformOptions is passed`, () => {
   const result = babelJest.process(
     sourceString,
@@ -39,3 +43,39 @@ test(`Returns source string with inline maps when no transformOptions is passed`
   expect(result.map.sources).toEqual(['dummy_path.js']);
   expect(JSON.stringify(result.map.sourcesContent)).toMatch('customMultiply');
 });
+
+test('getCacheKey does not depend on the rootDir', () => {
+  const getCacheKeyArgs = rootDir => {
+    const config = {
+      cwd: rootDir,
+      rootDir,
+    };
+
+    return [
+      '// Some code',
+      `${rootDir}/foo/bar.js`,
+      JSON.stringify(config),
+      {config, instrument: true, rootDir: config.rootDir},
+    ];
+  };
+
+  jest.mock('@babel/core');
+
+  require('@babel/core').loadPartialConfig = options => ({
+    babelrc: `${options.cwd}/foo/.babelrc`,
+    config: `${options.cwd}/babel.config.js`,
+    options: {
+      cwd: options.cwd,
+      someOtherOption: `${options.cwd}/foo`,
+    },
+  });
+
+  const cacheKeyForRoot1 = babelJest.getCacheKey(
+    ...getCacheKeyArgs('/root1/dir'),
+  );
+  const cacheKeyForRoot2 = babelJest.getCacheKey(
+    ...getCacheKeyArgs('/root2/dir'),
+  );
+
+  expect(cacheKeyForRoot1).toEqual(cacheKeyForRoot2);
+});

packages/babel-jest/src/index.ts

@@ -17,6 +17,7 @@ import {
   transformSync as babelTransform,
 } from '@babel/core';
 import chalk from 'chalk';
+import {escapeStrForRegex} from 'jest-regex-util';
 import slash from 'slash';
 
 const THIS_FILE = fs.readFileSync(__filename);
@@ -63,32 +64,57 @@ const createTransformer = (
     return babelConfig;
   }
 
+  const rootDirRegExpCache: {[rootDir: string]: RegExp} = Object.create(null);
+
+  function getRootDirRegExp(rootDir: Config.Path): RegExp {
+    if (!rootDirRegExpCache[rootDir]) {
+      rootDirRegExpCache[rootDir] = new RegExp(
+        `^${escapeStrForRegex(rootDir)}(?=${escapeStrForRegex(path.sep)}|$)`,
+      );
+    }
+
+    return rootDirRegExpCache[rootDir];
+  }
+
+  function getCacheKeyForBabelOptions(
+    babelOptions: PartialConfig,
+    rootDir: Config.Path,
+  ) {
+    const rootDirRegExp = getRootDirRegExp(rootDir);
+
+    // Not pretty but not coupled to a specific signature of the
+    // babel options to relativize paths
+    return JSON.stringify(babelOptions.options, (_key, value) => {
+      if (typeof value === 'string') {
+        return value.replace(rootDirRegExp, '<rootDir>');
+      }
+      return value;
+    });
+  }
+
   return {
     canInstrument: true,
     getCacheKey(
       fileData,
       filename,
-      configString,
+      _configString,
       {config, instrument, rootDir},
     ) {
       const babelOptions = loadBabelConfig(config.cwd, filename);
-      const configPath = [
-        babelOptions.config || '',
-        babelOptions.babelrc || '',
-      ];
+      const configPath = [babelOptions.config, babelOptions.babelrc].map(
+        configPath => configPath && path.relative(rootDir, configPath),
+      );
 
       return crypto
         .createHash('md5')
         .update(THIS_FILE)
         .update('\0', 'utf8')
-        .update(JSON.stringify(babelOptions.options))
+        .update(getCacheKeyForBabelOptions(babelOptions, rootDir))
         .update('\0', 'utf8')
         .update(fileData)
         .update('\0', 'utf8')
         .update(path.relative(rootDir, filename))
         .update('\0', 'utf8')
-        .update(configString)
-        .update('\0', 'utf8')
         .update(configPath.join(''))
         .update('\0', 'utf8')
         .update(instrument ? 'instrument' : '')

packages/babel-jest/tsconfig.json

@@ -7,6 +7,7 @@
   // TODO: include `babel-preset-jest` if it's ever in TS even though we don't care about its types
   "references": [
     {"path": "../jest-transform"},
-    {"path": "../jest-types"}
+    {"path": "../jest-types"},
+    {"path": "../jest-regex-util"}
   ]
 }