Function withFallback

packages/language-service/src/ts_plugin.ts:38–46

(
    fileName: string,
    cb: (ls: ts.LanguageService | LanguageService) => Result | undefined,
  )

  const ngLS = new LanguageService(project, tsLS, config);

  function withFallback<Result>(
    fileName: string,
    cb: (ls: ts.LanguageService | LanguageService) => Result | undefined,
  ): Result | undefined {
    if (angularOnly || !isTypeScriptFile(fileName)) {
      return cb(ngLS);
    }
    return cb(tsLS) ?? cb(ngLS);
  }

  function getSyntacticDiagnostics(fileName: string): ts.DiagnosticWithLocation[] {
    if (!angularOnly && isTypeScriptFile(fileName)) {