Class Logger

packages/angular_devkit/core/src/logger/logger.ts:33–174

export type LogLevel = 'debug' | 'info' | 'warn' | 'error' | 'fatal';

export class Logger extends Observable<LogEntry> implements LoggerApi {
  protected readonly _subject: Subject<LogEntry> = new Subject<LogEntry>();
  protected _metadata: LoggerMetadata;

  private _obs: Observable<LogEntry> = EMPTY;
  private _subscription: Subscription | null = null;

  protected get _observable() {
    return this._obs;
  }
  protected set _observable(v: Observable<LogEntry>) {
    if (this._subscription) {
      this._subscription.unsubscribe();
    }
    this._obs = v;
    if (this.parent) {
      this._subscription = this.subscribe(
        (value: LogEntry) => {
          if (this.parent) {
            this.parent._subject.next(value);
          }
        },
        (error: Error) => {
          if (this.parent) {
            this.parent._subject.error(error);
          }
        },
        () => {
          if (this._subscription) {
            this._subscription.unsubscribe();
          }
          this._subscription = null;
        },
      );
    }
  }

  constructor(
    public readonly name: string,
    public readonly parent: Logger | null = null,
  ) {
    super();

    const path: string[] = [];
    let p = parent;
    while (p) {
      path.push(p.name);
      p = p.parent;
    }
    this._metadata = { name, path };
    this._observable = this._subject.asObservable();
    if (this.parent && this.parent._subject) {
      // When the parent completes, complete us as well.
      this.parent._subject.subscribe(undefined, undefined, () => this.complete());
    }
  }

  asApi(): LoggerApi {