Method watch

lib/Compiler.js:530–540

* Returns a compiler watcher. * @param {WatchOptions} watchOptions the watcher's options * @param {Callback<Stats>} handler signals when the call finishes * @returns {Watching | undefined} a compiler watcher

(watchOptions, handler)

	 * @returns {Watching | undefined} a compiler watcher
	 */
	watch(watchOptions, handler) {
		if (this.running) {
			handler(new ConcurrentCompilationError());
			return;
		}

		this.running = true;
		this.watchMode = true;
		this.watching = new Watching(this, watchOptions, handler);
		return this.watching;
	}

	/**
	 * Processes the provided stat.