feat(jest-config): Allow using esbuild-register as TS loader

Signed-off-by: Matthew Peveler <[email protected]>

docs/Configuration.md

@@ -57,7 +57,7 @@ export default async (): Promise<Config> => {
 
 :::tip
 
-To read TypeScript configuration files Jest requires [`ts-node`](https://npmjs.com/package/ts-node). Make sure it is installed in your project.
+To read TypeScript configuration files Jest by default requires [`ts-node`](https://npmjs.com/package/ts-node). You can override this behavior by adding a `@jest-config-loader` docblock at the top of the file. Currently, [`ts-node`](https://npmjs.com/package/ts-node) and [`esbuild-register`](https://npmjs.com/package/esbuild-register) is supported. Make sure `ts-node` or the loader you specify is installed.
 
 :::
 

e2e/__tests__/readInitialOptions.test.ts

@@ -64,9 +64,21 @@ describe('readInitialOptions', () => {
     expect(config).toEqual({jestConfig: 'package.json', rootDir});
     expect(configPath).toEqual(configFile);
   });
-  test('should read a jest.config.ts file', async () => {
-    const configFile = resolveFixture('ts-config', 'jest.config.ts');
-    const rootDir = resolveFixture('ts-config');
+  test('should read a jest.config.ts file with ts-node', async () => {
+    const configFile = resolveFixture('ts-node-config', 'jest.config.ts');
+    const rootDir = resolveFixture('ts-node-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'jest.config.ts', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+  test('should read a jest.config.ts file with esbuild-register', async () => {
+    const configFile = resolveFixture(
+      'ts-esbuild-register-config',
+      'jest.config.ts',
+    );
+    const rootDir = resolveFixture('ts-esbuild-register-config');
     const {config, configPath} = await proxyReadInitialOptions(undefined, {
       cwd: rootDir,
     });

e2e/read-initial-options/ts-esbuild-register-config/jest.config.ts

@@ -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.
+ *
+ * @jest-config-loader esbuild-register
+ */
+export default {
+  jestConfig: 'jest.config.ts',
+};

packages/jest-config/package.json

@@ -18,12 +18,16 @@
   },
   "peerDependencies": {
     "@types/node": "*",
+    "esbuild-register": ">=3.1.0",
     "ts-node": ">=9.0.0"
   },
   "peerDependenciesMeta": {
     "@types/node": {
       "optional": true
     },
+    "esbuild-register": {
+      "optional": true
+    },
     "ts-node": {
       "optional": true
     }
@@ -39,6 +43,7 @@
     "glob": "^7.1.3",
     "graceful-fs": "^4.2.9",
     "jest-circus": "workspace:^",
+    "jest-docblock": "workspace:^",
     "jest-environment-node": "workspace:^",
     "jest-get-type": "workspace:^",
     "jest-regex-util": "workspace:^",
@@ -57,6 +62,8 @@
     "@types/graceful-fs": "^4.1.3",
     "@types/micromatch": "^4.0.1",
     "@types/parse-json": "^4.0.0",
+    "esbuild": "^0.15.0",
+    "esbuild-register": "^3.1.0",
     "semver": "^7.3.5",
     "ts-node": "^10.5.0",
     "typescript": "^4.8.2"

packages/jest-config/src/readConfigFileAndSetRootDir.ts

@@ -9,15 +9,21 @@ import * as path from 'path';
 import * as fs from 'graceful-fs';
 import parseJson = require('parse-json');
 import stripJsonComments = require('strip-json-comments');
-import type {Service} from 'ts-node';
 import type {Config} from '@jest/types';
+import {extract, parse} from 'jest-docblock';
 import {interopRequireDefault, requireOrImportModule} from 'jest-util';
 import {
   JEST_CONFIG_EXT_JSON,
   JEST_CONFIG_EXT_TS,
   PACKAGE_JSON,
 } from './constants';
 
+interface TsLoader {
+  enabled: (bool: boolean) => void;
+}
+
+type TsLoaderModule = 'ts-node' | 'esbuild-register';
+
 // Read the configuration and set its `rootDir`
 // 1. If it's a `package.json` file, we look into its "jest" property
 // 2. If it's a `jest.config.ts` file, we use `ts-node` to transpile & require it
@@ -82,7 +88,19 @@ const loadTSConfigFile = async (
   configPath: string,
 ): Promise<Config.InitialOptions> => {
   // Get registered TypeScript compiler instance
-  const registeredCompiler = await getRegisteredCompiler();
+  const docblockPragmas = parse(extract(fs.readFileSync(configPath, 'utf8')));
+  const tsLoader = docblockPragmas['jest-config-loader'] || 'ts-node';
+  if (Array.isArray(tsLoader)) {
+    throw new Error(
+      `You can only define a single test environment through docblocks, got "${tsLoader.join(
+        ', ',
+      )}"`,
+    );
+  }
+
+  const registeredCompiler = await getRegisteredCompiler(
+    tsLoader as TsLoaderModule,
+  );
 
   registeredCompiler.enabled(true);
 
@@ -98,30 +116,50 @@ const loadTSConfigFile = async (
   return configObject;
 };
 
-let registeredCompilerPromise: Promise<Service>;
+let registeredCompilerPromise: Promise<TsLoader>;
 
-function getRegisteredCompiler() {
+function getRegisteredCompiler(loader: TsLoaderModule) {
   // Cache the promise to avoid multiple registrations
-  registeredCompilerPromise = registeredCompilerPromise ?? registerTsNode();
+  registeredCompilerPromise =
+    registeredCompilerPromise ?? registerTsLoader(loader);
   return registeredCompilerPromise;
 }
 
-async function registerTsNode(): Promise<Service> {
+async function registerTsLoader(loader: TsLoaderModule): Promise<TsLoader> {
   try {
     // Register TypeScript compiler instance
-    const tsNode = await import('ts-node');
-    return tsNode.register({
-      compilerOptions: {
-        module: 'CommonJS',
-      },
-      moduleTypes: {
-        '**': 'cjs',
-      },
-    });
+    if (loader === 'ts-node') {
+      const tsLoader = await import('ts-node');
+      return tsLoader.register({
+        compilerOptions: {
+          module: 'CommonJS',
+        },
+        moduleTypes: {
+          '**': 'cjs',
+        },
+      });
+    } else if (loader === 'esbuild-register') {
+      const tsLoader = await import('esbuild-register/dist/node');
+      let instance: {unregister: () => void} | undefined;
+      return {
+        enabled: (bool: boolean) => {
+          if (bool) {
+            instance = tsLoader.register({
+              target: `node${process.version.slice(1)}`,
+            });
+          } else {
+            instance?.unregister();
+          }
+        },
+      };
+    }
+    throw new Error(
+      `Jest: '${loader}' is not a valid TypeScript configuration loader.`,
+    );
   } catch (e: any) {
     if (e.code === 'ERR_MODULE_NOT_FOUND') {
       throw new Error(
-        `Jest: 'ts-node' is required for the TypeScript configuration files. Make sure it is installed\nError: ${e.message}`,
+        `Jest: '${loader}' is required for the TypeScript configuration files. Make sure it is installed\nError: ${e.message}`,
       );
     }
 

packages/jest-config/tsconfig.json

@@ -10,6 +10,7 @@
   // jest-test-sequencer, but that is just `require.resolve`d, so no real use
   // for their types
   "references": [
+    {"path": "../jest-docblock"},
     {"path": "../jest-environment-node"},
     {"path": "../jest-get-type"},
     {"path": "../jest-regex-util"},