feat(config): add read initial options helper

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Features
 
+- `[jest-config]` Add `readInitialConfig` utility function ([#13356](https://github.com/facebook/jest/pull/13356))
 - `[jest-core]` Enable testResultsProcessor to be async ([#13343](https://github.com/facebook/jest/pull/13343))
 - `[expect, @jest/expect-utils]` Allow `isA` utility to take a type argument ([#13355](https://github.com/facebook/jest/pull/13355))
 

e2e/__tests__/readInitialOptions.test.ts

@@ -0,0 +1,148 @@
+/**
+ * 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 path = require('path');
+import execa = require('execa');
+import type {ReadJestConfigOptions, readInitialOptions} from 'jest-config';
+
+function resolveFixture(...pathSegments: Array<string>) {
+  return path.resolve(__dirname, '..', 'read-initial-options', ...pathSegments);
+}
+
+interface ProxyReadJestConfigOptions extends ReadJestConfigOptions {
+  cwd?: string;
+}
+
+/**
+ * These e2e tests are running via a child process, because we're running in a VM and are not allowed to `import` directly
+ * It also represents a more real-world example of how to run.
+ */
+async function proxyReadInitialOptions(
+  configFile?: string | undefined,
+  options?: ProxyReadJestConfigOptions,
+): ReturnType<typeof readInitialOptions> {
+  const {stdout} = await execa(
+    'node',
+    [
+      require.resolve('../read-initial-options/readOptions.js'),
+      configFile ?? '',
+      JSON.stringify(options),
+    ],
+    {cwd: options?.cwd},
+  );
+  return JSON.parse(stdout);
+}
+
+describe('readInitialOptions', () => {
+  test('should read from the cwd by default', async () => {
+    const configFile = resolveFixture('js-config', 'jest.config.js');
+    const rootDir = resolveFixture('js-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'jest.config.js', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+  test('should read a jest.config.js file', async () => {
+    const configFile = resolveFixture('js-config', 'jest.config.js');
+    const rootDir = resolveFixture('js-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'jest.config.js', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+  test('should read a package.json file', async () => {
+    const configFile = resolveFixture('pkg-config', 'package.json');
+    const rootDir = resolveFixture('pkg-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    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');
+    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.mjs file', async () => {
+    const configFile = resolveFixture('mjs-config', 'jest.config.mjs');
+    const rootDir = resolveFixture('mjs-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'jest.config.mjs', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+  test('should read a jest.config.json file', async () => {
+    const configFile = resolveFixture('json-config', 'jest.config.json');
+    const rootDir = resolveFixture('json-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'jest.config.json', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+  test('should read a jest config exporting an async function', async () => {
+    const configFile = resolveFixture('async-config', 'jest.config.js');
+    const rootDir = resolveFixture('async-config');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd: rootDir,
+    });
+    expect(config).toEqual({jestConfig: 'async-config', rootDir});
+    expect(configPath).toEqual(configFile);
+  });
+
+  test('should be able to skip config reading, instead read from cwd', async () => {
+    const expectedConfigFile = resolveFixture(
+      'json-config',
+      'jest.config.json',
+    );
+    const {config, configPath} = await proxyReadInitialOptions(
+      resolveFixture('js-config', 'jest.config.js'),
+      {
+        cwd: resolveFixture('json-config'),
+        readFromCwd: true,
+      },
+    );
+
+    expect(config).toEqual({
+      jestConfig: 'jest.config.json',
+      rootDir: path.dirname(expectedConfigFile),
+    });
+    expect(configPath).toEqual(expectedConfigFile);
+  });
+
+  test('should give an error when there are multiple config files', async () => {
+    const cwd = resolveFixture('multiple-config-files');
+    const error: Error = await proxyReadInitialOptions(undefined, {cwd}).catch(
+      error => error,
+    );
+    expect(error.message).toContain('Multiple configurations found');
+    expect(error.message).toContain('multiple-config-files/jest.config.js');
+    expect(error.message).toContain('multiple-config-files/jest.config.json');
+  });
+
+  test('should be able to ignore multiple config files error', async () => {
+    const cwd = resolveFixture('multiple-config-files');
+    const {config, configPath} = await proxyReadInitialOptions(undefined, {
+      cwd,
+      skipMultipleConfigError: true,
+    });
+    expect(config).toEqual({
+      jestConfig: 'jest.config.js',
+      rootDir: resolveFixture('multiple-config-files'),
+    });
+    expect(configPath).toEqual(
+      resolveFixture('multiple-config-files', 'jest.config.js'),
+    );
+  });
+});

e2e/read-initial-options/async-config/jest.config.js

@@ -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.
+ */
+module.exports = async function () {
+  return {
+    jestConfig: 'async-config',
+  };
+};

e2e/read-initial-options/js-config/jest.config.js

@@ -0,0 +1,9 @@
+/**
+ * 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 = {
+  jestConfig: 'jest.config.js',
+};

e2e/read-initial-options/json-config/jest.config.json

@@ -0,0 +1,3 @@
+{
+  "jestConfig": "jest.config.json"
+}

e2e/read-initial-options/mjs-config/jest.config.mjs

@@ -0,0 +1,9 @@
+/**
+ * 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.
+ */
+export default {
+  jestConfig: 'jest.config.mjs',
+};

e2e/read-initial-options/multiple-config-files/jest.config.js

@@ -0,0 +1,9 @@
+/**
+ * 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 = {
+  jestConfig: 'jest.config.js',
+};

e2e/read-initial-options/multiple-config-files/jest.config.json

@@ -0,0 +1,3 @@
+{
+  "jestConfig": "jest.config.json"
+}

e2e/read-initial-options/pkg-config/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "jestConfig": "package.json"
+  }
+}

e2e/read-initial-options/readOptions.js

@@ -0,0 +1,22 @@
+/**
+ * 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.
+ */
+const {readInitialOptions} = require('jest-config');
+async function readConfig() {
+  let config = process.argv[2];
+  let options = undefined;
+  if (config === '') {
+    config = undefined;
+  }
+  if (process.argv[3]) {
+    options = JSON.parse(process.argv[3]);
+  }
+  console.log(JSON.stringify(await readInitialOptions(config, options)));
+}
+readConfig().catch(err => {
+  console.error(err);
+  process.exitCode = 1;
+});

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

@@ -0,0 +1,9 @@
+/**
+ * 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.
+ */
+export default {
+  jestConfig: 'jest.config.ts',
+};

packages/jest-config/src/__tests__/readInitialOptions.test.ts

@@ -0,0 +1,30 @@
+/**
+ * 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 type {Config} from '@jest/types';
+import {readInitialOptions} from '../index';
+
+describe(readInitialOptions, () => {
+  test('should be able to use serialized jest config', async () => {
+    const inputConfig = {jestConfig: 'serialized'};
+    const {config, configPath} = await readInitialOptions(
+      JSON.stringify(inputConfig),
+    );
+    expect(config).toEqual({...inputConfig, rootDir: process.cwd()});
+    expect(configPath).toBeNull();
+  });
+
+  test('should allow deserialized options', async () => {
+    const inputConfig = {jestConfig: 'deserialized'};
+    const {config, configPath} = await readInitialOptions(undefined, {
+      packageRootOrConfig: inputConfig as Config.InitialOptions,
+      parentConfigDirname: process.cwd(),
+    });
+    expect(config).toEqual({...inputConfig, rootDir: process.cwd()});
+    expect(configPath).toBeNull();
+  });
+  // Note: actual file reading is tested in e2e test
+});