Function loadTsconfigFromExtends

src/tsconfig-loader.ts:171–212

* Intended to be called only from loadTsconfig. * Parameters don't have defaults because they should use the same as loadTsconfig.

(
  configFilePath: string,
  extendedConfigValue: string,
  // eslint-disable-next-line no-shadow
  existsSync: (path: string) => boolean,
  readFileSync: (filename: string) => string
)

 * Parameters don't have defaults because they should use the same as loadTsconfig.
 */
function loadTsconfigFromExtends(
  configFilePath: string,
  extendedConfigValue: string,
  // eslint-disable-next-line no-shadow
  existsSync: (path: string) => boolean,
  readFileSync: (filename: string) => string
): Tsconfig {
  if (
    typeof extendedConfigValue === "string" &&
    extendedConfigValue.indexOf(".json") === -1
  ) {
    extendedConfigValue += ".json";
  }
  const currentDir = path.dirname(configFilePath);
  let extendedConfigPath = path.join(currentDir, extendedConfigValue);
  if (
    extendedConfigValue.indexOf("/") !== -1 &&
    extendedConfigValue.indexOf(".") !== -1 &&
    !existsSync(extendedConfigPath)
  ) {
    extendedConfigPath = path.join(
      currentDir,
      "node_modules",
      extendedConfigValue
    );
  }

  const config =
    loadTsconfig(extendedConfigPath, existsSync, readFileSync) || {};

  // baseUrl should be interpreted as relative to extendedConfigPath,
  // but we need to update it so it is relative to the original tsconfig being loaded
  if (config.compilerOptions?.baseUrl) {
    const extendsDir = path.dirname(extendedConfigValue);
    config.compilerOptions.baseUrl = path.join(
      extendsDir,
      config.compilerOptions.baseUrl
    );
  }

  return config;
}

function mergeTsconfigs(
  base: Tsconfig | undefined,