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 +1,101 @@
+/**
+ * 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 {readInitialOptions} from 'jest-config';
+
+function resolveFixture(...pathSegments: Array<string>) {
+  return path.resolve(__dirname, '..', 'read-initial-options', ...pathSegments);
+}
+
+describe(readInitialOptions.name, () => {
+  test('should read from the cwd by default', async () => {
+    const configFile = resolveFixture('js-config', 'jest.config.js');
+    const rootDir = resolveFixture('js-config');
+    jest.spyOn(process, 'cwd').mockReturnValue(rootDir);
+    const {config, configPath} = await readInitialOptions();
+    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 readInitialOptions(configFile);
+    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 readInitialOptions(configFile);
+    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 readInitialOptions(configFile);
+    expect(config).toEqual({jestConfig: 'jest.config.ts', 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 readInitialOptions(configFile);
+    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 readInitialOptions(configFile);
+    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',
+    );
+    jest.spyOn(process, 'cwd').mockReturnValue(resolveFixture('json-config'));
+    const {config, configPath} = await readInitialOptions(
+      resolveFixture('js-config', 'jest.config.js'),
+      {
+        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');
+    jest.spyOn(process, 'cwd').mockReturnValue(cwd);
+    const error: Error = await readInitialOptions().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');
+    jest.spyOn(process, 'cwd').mockReturnValue(cwd);
+    const {config, configPath} = await readInitialOptions(undefined, {
+      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/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/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-runner';
+import {readInitialOptions} from '../index';
+
+describe(readInitialOptions.name, () => {
+  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).toEqual(null);
+  });
+
+  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).toEqual(null);
+  });
+  // Note: actual file reading is tested in e2e test
+});

packages/jest-config/src/index.ts

@@ -43,56 +43,18 @@ export async function readConfig(
   projectIndex = Infinity,
   skipMultipleConfigError = false,
 ): Promise<ReadConfig> {
-  let rawOptions: Config.InitialOptions;
-  let configPath = null;
-
-  if (typeof packageRootOrConfig !== 'string') {
-    if (parentConfigDirname) {
-      rawOptions = packageRootOrConfig;
-      rawOptions.rootDir = rawOptions.rootDir
-        ? replaceRootDirInPath(parentConfigDirname, rawOptions.rootDir)
-        : parentConfigDirname;
-    } else {
-      throw new Error(
-        'Jest: Cannot use configuration as an object without a file path.',
-      );
-    }
-  } else if (isJSONString(argv.config)) {
-    // A JSON string was passed to `--config` argument and we can parse it
-    // and use as is.
-    let config;
-    try {
-      config = JSON.parse(argv.config);
-    } catch {
-      throw new Error(
-        'There was an error while parsing the `--config` argument as a JSON string.',
-      );
-    }
-
-    // NOTE: we might need to resolve this dir to an absolute path in the future
-    config.rootDir = config.rootDir || packageRootOrConfig;
-    rawOptions = config;
-    // A string passed to `--config`, which is either a direct path to the config
-    // or a path to directory containing `package.json`, `jest.config.js` or `jest.config.ts`
-  } else if (!skipArgvConfigOption && typeof argv.config == 'string') {
-    configPath = resolveConfigPath(
-      argv.config,
-      process.cwd(),
-      skipMultipleConfigError,
-    );
-    rawOptions = await readConfigFileAndSetRootDir(configPath);
-  } else {
-    // Otherwise just try to find config in the current rootDir.
-    configPath = resolveConfigPath(
+  const {config: initialOptions, configPath} = await readInitialOptions(
+    argv?.config,
+    {
       packageRootOrConfig,
-      process.cwd(),
+      parentConfigDirname,
+      readFromCwd: skipArgvConfigOption,
       skipMultipleConfigError,
-    );
-    rawOptions = await readConfigFileAndSetRootDir(configPath);
-  }
+    },
+  );
 
   const {options, hasDeprecationWarnings} = await normalize(
-    rawOptions,
+    initialOptions,
     argv,
     configPath,
     projectIndex,
@@ -267,6 +229,91 @@ This usually means that your ${chalk.bold(
   }
 };
 
+export interface ReadJestConfigOptions {
+  /**
+   * The package root or deserialized config (default is cwd)
+   */
+  packageRootOrConfig?: string | Config.InitialOptions;
+  /**
+   * When the `packageRootOrConfig` contains config, this parameter should
+   * contain the dirname of the parent config
+   */
+  parentConfigDirname?: null | string;
+  /**
+   * Indicates whether or not to read the specified config file from disk.
+   * When true, jest will read try to read config from the current working directory.
+   * (default is false)
+   */
+  readFromCwd?: boolean;
+  /**
+   * Indicates whether or not to ignore the error of jest finding multiple config files.
+   * (default is false)
+   */
+  skipMultipleConfigError?: boolean;
+}
+
+/**
+ * Reads the jest config, without validating them or filling it out with defaults.
+ * @param config The path to the file or serialized config.
+ * @param param1 Additional options
+ * @returns The raw initial config (not validated)
+ */
+export async function readInitialOptions(
+  config?: string,
+  {
+    packageRootOrConfig = process.cwd(),
+    parentConfigDirname = null,
+    readFromCwd = false,
+    skipMultipleConfigError = false,
+  }: ReadJestConfigOptions = {},
+): Promise<{config: Config.InitialOptions; configPath: string | null}> {
+  if (typeof packageRootOrConfig !== 'string') {
+    if (parentConfigDirname) {
+      const rawOptions = packageRootOrConfig;
+      rawOptions.rootDir = rawOptions.rootDir
+        ? replaceRootDirInPath(parentConfigDirname, rawOptions.rootDir)
+        : parentConfigDirname;
+      return {config: rawOptions, configPath: null};
+    } else {
+      throw new Error(
+        'Jest: Cannot use configuration as an object without a file path.',
+      );
+    }
+  } else if (isJSONString(config)) {
+    // A JSON string was passed to `--config` argument and we can parse it
+    // and use as is.
+    let initialOptions;
+    try {
+      initialOptions = JSON.parse(config);
+    } catch {
+      throw new Error(
+        'There was an error while parsing the `--config` argument as a JSON string.',
+      );
+    }
+
+    // NOTE: we might need to resolve this dir to an absolute path in the future
+    initialOptions.rootDir = initialOptions.rootDir || packageRootOrConfig;
+    return {config: initialOptions, configPath: null};
+    // A string passed to `--config`, which is either a direct path to the config
+    // or a path to directory containing `package.json`, `jest.config.js` or `jest.config.ts`
+  } else if (!readFromCwd && typeof config == 'string') {
+    const configPath = resolveConfigPath(
+      config,
+      process.cwd(),
+      skipMultipleConfigError,
+    );
+    return {config: await readConfigFileAndSetRootDir(configPath), configPath};
+  } else {
+    // Otherwise just try to find config in the current rootDir.
+    const configPath = resolveConfigPath(
+      packageRootOrConfig,
+      process.cwd(),
+      skipMultipleConfigError,
+    );
+    return {config: await readConfigFileAndSetRootDir(configPath), configPath};
+  }
+}
+
 // Possible scenarios:
 //  1. jest --config config.json
 //  2. jest --projects p1 p2