chore: migrate babel-jest to TypeScript

Author: SimenB

CHANGELOG.md

@@ -25,6 +25,7 @@
 - `[jest-watcher]`: Migrate to TypeScript ([#7843](https://github.com/facebook/jest/pull/7843))
 - `[jest-mock]`: Migrate to TypeScript ([#7847](https://github.com/facebook/jest/pull/7847), [#7850](https://github.com/facebook/jest/pull/7850))
 - `[jest-worker]`: Migrate to TypeScript ([#7853](https://github.com/facebook/jest/pull/7853))
+- `[babel-jest]`: Migrate to TypeScript
 
 ### Performance
 

packages/babel-jest/package.json

@@ -9,7 +9,9 @@
   },
   "license": "MIT",
   "main": "build/index.js",
+  "types": "build/index.d.ts",
   "dependencies": {
+    "@jest/types": "^24.1.0",
     "babel-plugin-istanbul": "^5.1.0",
     "babel-preset-jest": "^24.1.0",
     "chalk": "^2.4.2",

packages/babel-jest/src/__tests__/index.js renamed to packages/babel-jest/src/__tests__/index.ts

@@ -4,7 +4,9 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
-const babelJest = require('../index');
+
+import {Config, Transform} from '@jest/types';
+import babelJest from '../index';
 
 //Mock data for all the tests
 const sourceString = `
@@ -24,12 +26,16 @@ const mockConfig = {
 };
 
 test(`Returns source string with inline maps when no transformOptions is passed`, () => {
-  const result = babelJest.process(sourceString, 'dummy_path.js', mockConfig);
+  const result = babelJest.process(
+    sourceString,
+    'dummy_path.js',
+    (mockConfig as unknown) as Config.ProjectConfig,
+  ) as Transform.TransformedSource;
   expect(typeof result).toBe('object');
   expect(result.code).toBeDefined();
   expect(result.map).toBeDefined();
   expect(result.code).toMatch('//# sourceMappingURL');
   expect(result.code).toMatch('customMultiply');
-  expect(result.map.sources).toEqual(['dummy_path.js']);
-  expect(JSON.stringify(result.map.sourcesContent)).toMatch('customMultiply');
+  expect(result.map!.sources).toEqual(['dummy_path.js']);
+  expect(JSON.stringify(result.map!.sourcesContent)).toMatch('customMultiply');
 });

packages/babel-jest/src/index.js renamed to packages/babel-jest/src/index.ts

@@ -3,32 +3,31 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
- *
- * @flow
  */
 
-import type {Path, ProjectConfig} from 'types/Config';
-import type {
-  CacheKeyOptions,
-  Transformer,
-  TransformOptions,
-  TransformedSource,
-} from 'types/Transform';
-
 import crypto from 'crypto';
 import fs from 'fs';
 import path from 'path';
-import {transformSync as babelTransform, loadPartialConfig} from '@babel/core';
+import {Config, Transform} from '@jest/types';
+import {
+  transformSync as babelTransform,
+  loadPartialConfig,
+  TransformOptions,
+  PartialConfig,
+} from '@babel/core';
 import chalk from 'chalk';
 import slash from 'slash';
 
 const THIS_FILE = fs.readFileSync(__filename);
 const jestPresetPath = require.resolve('babel-preset-jest');
 const babelIstanbulPlugin = require.resolve('babel-plugin-istanbul');
 
-const createTransformer = (options: any): Transformer => {
+const createTransformer = (
+  options: TransformOptions = {},
+): Transform.Transformer => {
   options = {
     ...options,
+    // @ts-ignore: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/32955
     caller: {
       name: 'babel-jest',
       supportsStaticESM: false,
@@ -39,10 +38,13 @@ const createTransformer = (options: any): Transformer => {
     sourceMaps: 'both',
   };
 
+  // @ts-ignore: seems like this is removed. Is that true?
   delete options.cacheDirectory;
-  delete options.filename;
 
-  function loadBabelConfig(cwd, filename) {
+  function loadBabelConfig(
+    cwd: Config.Path,
+    filename: Config.Path,
+  ): PartialConfig {
     // `cwd` first to allow incoming options to override it
     const babelConfig = loadPartialConfig({cwd, ...options, filename});
 
@@ -63,9 +65,13 @@ const createTransformer = (options: any): Transformer => {
     canInstrument: true,
     getCacheKey(
       fileData: string,
-      filename: Path,
+      filename: Config.Path,
       configString: string,
-      {config, instrument, rootDir}: {config: ProjectConfig} & CacheKeyOptions,
+      {
+        config,
+        instrument,
+        rootDir,
+      }: {config: Config.ProjectConfig} & Transform.CacheKeyOptions,
     ): string {
       const babelOptions = loadBabelConfig(config.cwd, filename);
       const configPath = [
@@ -96,16 +102,16 @@ const createTransformer = (options: any): Transformer => {
     },
     process(
       src: string,
-      filename: Path,
-      config: ProjectConfig,
-      transformOptions?: TransformOptions,
-    ): string | TransformedSource {
+      filename: Config.Path,
+      config: Config.ProjectConfig,
+      transformOptions?: Transform.TransformOptions,
+    ): string | Transform.TransformedSource {
       const babelOptions = {...loadBabelConfig(config.cwd, filename).options};
 
       if (transformOptions && transformOptions.instrument) {
         babelOptions.auxiliaryCommentBefore = ' istanbul ignore next ';
         // Copied from jest-runtime transform.js
-        babelOptions.plugins = babelOptions.plugins.concat([
+        babelOptions.plugins = (babelOptions.plugins || []).concat([
           [
             babelIstanbulPlugin,
             {
@@ -119,10 +125,21 @@ const createTransformer = (options: any): Transformer => {
 
       const transformResult = babelTransform(src, babelOptions);
 
-      return transformResult || src;
+      if (transformResult && typeof transformResult.code === 'string') {
+        // @ts-ignore: why doesn't TS understand this?
+        return transformResult;
+      }
+
+      return src;
     },
   };
 };
 
-module.exports = createTransformer();
-(module.exports: any).createTransformer = createTransformer;
+const transformer = createTransformer();
+
+// FIXME: This is not part of the exported TS types. When fixed, remember to
+// move @types/babel__core to `dependencies` instead of `devDependencies`
+// (one fix is to use ESM, maybe for Jest 25?)
+transformer.createTransformer = createTransformer;
+
+export = transformer;

packages/babel-jest/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "build"
+  },
+  "references": [{"path": "../jest-types"}]
+}

packages/jest-types/src/Transform.ts

@@ -0,0 +1,58 @@
+/**
+ * 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 {Script} from 'vm';
+import {Path, ProjectConfig} from './Config';
+
+export type TransformedSource = {
+  code: string;
+  map?: // copied from https://github.com/DefinitelyTyped/DefinitelyTyped/blob/363cdf403a74e0372e87bbcd15eb1668f4c5230b/types/babel__core/index.d.ts#L371-L379
+  {
+    version: number;
+    sources: string[];
+    names: string[];
+    sourceRoot?: string;
+    sourcesContent?: string[];
+    mappings: string;
+    file: string;
+  } | null;
+};
+
+export type TransformResult = {
+  script: Script;
+  mapCoverage: boolean;
+  sourceMapPath?: string;
+};
+
+export type TransformOptions = {
+  instrument: boolean;
+};
+
+export type CacheKeyOptions = {
+  config: ProjectConfig;
+  instrument: boolean;
+  rootDir: string;
+};
+
+export type Transformer = {
+  canInstrument?: boolean;
+  createTransformer?: (options: any) => Transformer;
+
+  getCacheKey: (
+    fileData: string,
+    filePath: Path,
+    configStr: string,
+    options: CacheKeyOptions,
+  ) => string;
+
+  process: (
+    sourceText: string,
+    sourcePath: Path,
+    config: ProjectConfig,
+    options?: TransformOptions,
+  ) => string | TransformedSource;
+};

packages/jest-types/src/index.ts

@@ -10,5 +10,6 @@ import * as Console from './Console';
 import * as SourceMaps from './SourceMaps';
 import * as TestResult from './TestResult';
 import * as Mocks from './Mocks';
+import * as Transform from './Transform';
 
-export {Config, Console, SourceMaps, TestResult, Mocks};
+export {Config, Console, SourceMaps, TestResult, Mocks, Transform};