readConfigFileAndSetRootDir.ts

/**
 * 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 * as path from 'path';
import {pathToFileURL} from 'url';
import * as fs from 'graceful-fs';
import type {Config} from '@jest/types';
// @ts-ignore: vendored
import jsonlint from './vendor/jsonlint';
import {JEST_CONFIG_EXT_JSON, PACKAGE_JSON} from './constants';

// Read the configuration and set its `rootDir`
// 1. If it's a `package.json` file, we look into its "jest" property
// 2. For any other file, we just require it. If we receive an 'ERR_REQUIRE_ESM'
//    from node, perform a dynamic import instead.
export default async function readConfigFileAndSetRootDir(
  configPath: Config.Path,
): Promise<Config.InitialOptions> {
  const isJSON = configPath.endsWith(JEST_CONFIG_EXT_JSON);
  let configObject;

  try {
    configObject = require(configPath);
  } catch (error) {
    if (error.code === 'ERR_REQUIRE_ESM') {
      try {
        const configUrl = pathToFileURL(configPath);

        // node `import()` supports URL, but TypeScript doesn't know that
        const importedConfig = await import(configUrl.href);

        if (!importedConfig.default) {
          throw new Error(
            `Jest: Failed to load mjs config file ${configPath} - did you use a default export?`,
          );
        }

        configObject = importedConfig.default;
      } catch (innerError) {
        if (innerError.message === 'Not supported') {
          throw new Error(
            `Jest: Your version of Node does not support dynamic import - please enable it or use a .cjs file extension for file ${configPath}`,
          );
        }

        throw innerError;
      }
    } else if (isJSON) {
      throw new Error(
        `Jest: Failed to parse config file ${configPath}\n` +
          `  ${jsonlint.errors(fs.readFileSync(configPath, 'utf8'))}`,
      );
    } else {
      throw error;
    }
  }

  if (configPath.endsWith(PACKAGE_JSON)) {
    // Event if there's no "jest" property in package.json we will still use
    // an empty object.
    configObject = configObject.jest || {};
  }

  if (configObject.rootDir) {
    // We don't touch it if it has an absolute path specified
    if (!path.isAbsolute(configObject.rootDir)) {
      // otherwise, we'll resolve it relative to the file's __dirname
      configObject.rootDir = path.resolve(
        path.dirname(configPath),
        configObject.rootDir,
      );
    }
  } else {
    // If rootDir is not there, we'll set it to this file's __dirname
    configObject.rootDir = path.dirname(configPath);
  }

  return configObject;
}