Method invalidate

lib/Server.js:3468–3511

* @param {import("webpack-dev-middleware").Callback=} callback callback

(callback = () => {})

   * @param {import("webpack-dev-middleware").Callback=} callback callback
   */
  invalidate(callback = () => {}) {
    // In plugin mode the host owns `compiler.watch()`, so the middleware has no
    // `watching` of its own — invalidate the host's watching(s) directly to
    // trigger a rebuild (each child's own `watching` for a `MultiCompiler`).
    if (this.isPlugin) {
      const compilers =
        /** @type {MultiCompiler} */ (this.compiler).compilers ||
        /** @type {Compiler[]} */ ([this.compiler]);

      /** @type {NonNullable<Compiler["watching"]>[]} */
      const watchings = [];

      for (const compiler of compilers) {
        if (compiler.watching) {
          watchings.push(compiler.watching);
        }
      }

      if (watchings.length === 0) {
        callback();
        return;
      }

      let pending = watchings.length;

      const onInvalidated = () => {
        pending -= 1;

        if (pending === 0) {
          callback();
        }
      };

      for (const watching of watchings) {
        watching.invalidate(onInvalidated);
      }

      return;
    }

    if (this.middleware) {
      this.middleware.invalidate(callback);
    }
  }

  /**
   * @returns {Promise<void>}