Function readConfiguration

packages/compiler-cli/src/perform_compile.ts:75–181

(
  project: string,
  existingOptions?: api.CompilerOptions,
  host: ConfigurationHost = getFileSystem(),
)

}

export function readConfiguration(
  project: string,
  existingOptions?: api.CompilerOptions,
  host: ConfigurationHost = getFileSystem(),
): ParsedConfiguration {
  try {
    const fs = getFileSystem();

    const readConfigFile = (configFile: string) =>
      ts.readConfigFile(configFile, (file) => host.readFile(host.resolve(file)));
    const readAngularCompilerOptions = (
      configFile: string,
      parentOptions: NgCompilerOptions = {},
    ): NgCompilerOptions => {
      const {config, error} = readConfigFile(configFile);

      if (error) {
        // Errors are handled later on by 'parseJsonConfigFileContent'
        return parentOptions;
      }

      // Note: In Google, `angularCompilerOptions` are stored in `bazelOptions`.
      // This function typically doesn't run for actual Angular compilations, but
      // tooling like Tsurge, or schematics may leverage this helper, so we account
      // for this here.
      const angularCompilerOptions =
        config.angularCompilerOptions ?? config.bazelOptions?.angularCompilerOptions;

      // we are only interested into merging 'angularCompilerOptions' as
      // other options like 'compilerOptions' are merged by TS
      let existingNgCompilerOptions = {...angularCompilerOptions, ...parentOptions};
      if (!config.extends) {
        return existingNgCompilerOptions;
      }

      const extendsPaths: string[] =
        typeof config.extends === 'string' ? [config.extends] : config.extends;

      // Call readAngularCompilerOptions recursively to merge NG Compiler options
      // Reverse the array so the overrides happen from right to left.
      return [...extendsPaths].reverse().reduce((prevOptions, extendsPath) => {
        const extendedConfigPath = getExtendedConfigPath(configFile, extendsPath, host, fs);

        return extendedConfigPath === null
          ? prevOptions
          : readAngularCompilerOptions(extendedConfigPath, prevOptions);
      }, existingNgCompilerOptions);
    };

    const {projectFile, basePath} = calcProjectFileAndBasePath(project, host);
    const configFileName = host.resolve(host.pwd(), projectFile);
    const {config, error} = readConfigFile(projectFile);

    if (error) {
      return {
        project,
        errors: [error],
        rootNames: [],