docs(loader): update Rule.use.parallel to include maxWorkers option (#12322)

* docs(loader): update Rule.use.parallel to include maxWorkers option

* Apply suggestion from @chenjiahan

* docs: fix

Author: chenjiahan

packages/rspack/src/config/types.ts

@@ -882,6 +882,15 @@ export type RuleSetLoaderWithOptions = {
 
 	loader: RuleSetLoader;
 
+	/**
+	 * Controls whether a given loader should run in worker threads for parallel execution. Loaders marked
+	 * with `parallel` are scheduled across multiple threads, reducing pressure on the main thread and improving
+	 * overall build performance.
+	 * - When set to `true`, the loader runs in a worker. Rspack automatically selects an appropriate number of
+	 * worker threads.
+	 * - When set to `{ maxWorkers }`, you can explicitly define the maximum number of workers to use.
+	 * - When set to `false` or omitted, the loader runs on the main thread.
+	 */
 	parallel?: boolean | { maxWorkers?: number };
 
 	options?: RuleSetLoaderOptions;

website/docs/en/config/module.mdx

@@ -2646,7 +2646,13 @@ export default {
 - **Type**: `boolean`
 - **Default:** `false`
 
-In version 1.3.1, the `Rule.use.parallel` configuration option was introduced. When enabled for corresponding loaders and `experiments.parallelLoader = true` is configured, the respective loaders will be executed in worker threads:
+Controls whether a given loader should run in worker threads for parallel execution. Loaders marked with `parallel` are scheduled across multiple threads, reducing pressure on the main thread and improving overall build performance.
+
+- When set to `true`, the loader runs in a worker. Rspack automatically selects an appropriate number of worker threads.
+- When set to `{ maxWorkers }`, you can explicitly define the maximum number of workers to use.
+- When set to `false` or omitted, the loader runs on the main thread.
+
+For example, enabling parallel execution for `less-loader`:
 
 ```js title="rspack.config.mjs"
 export default {
@@ -2672,13 +2678,13 @@ export default {
 };
 ```
 
-When multiple loaders in the current `Rule` are configured with `Rule.use.parallel = true`, Rspack will execute all loader tasks in the same worker until it encounters the next loader without the `parallel` flag or a Rust `builtin:` loader. This approach enhances loader parallel performance.
+When multiple loaders within the same rule have `parallel` enabled, Rspack executes them sequentially inside the same worker until it encounters a non-parallel loader or a Rust-implemented builtin loader. This preserves loader order while maximizing parallel efficiency.
 
-:::warning
+:::tip
 
-- This configuration only takes effect when [experiments.parallelLoader](/config/experiments#experimentsparallelloader) is enabled.
-- The loader configuration must comply with the [HTML structured clone algorithm](https://nodejs.org/api/worker_threads.html#portpostmessagevalue-transferlist), otherwise transmission will fail.
-- Currently, Rspack does not support most of the methods on `LoaderContext._compilation`, `LoaderContext._compiler`, `LoaderContext._module`.
+- This feature is experimental. It only takes effect when [experiments.parallelLoader](/config/experiments#experimentsparallelloader) is enabled.
+- The loader options must comply with the [HTML structured clone algorithm](https://nodejs.org/api/worker_threads.html#portpostmessagevalue-transferlist), otherwise transmission will fail.
+- In worker mode, most methods on `LoaderContext._compilation`, `LoaderContext._compiler`, `LoaderContext._module` are not supported.
 
 :::
 

website/docs/zh/config/module.mdx

@@ -2640,10 +2640,16 @@ export default {
 
 <ApiMeta addedVersion="1.3.1" />
 
-- **类型**: `boolean`
+- **类型**: `boolean | { maxWorkers?: number }`
 - **默认值:** `false`
 
-在 1.3.1 版本中支持了 `Rule.use.parallel` 配置项，当对对应 loader 开启并配置 `experiments.parallelLoader = true` 后，对应的 loader 会被发送到 worker threads 执行：
+用于将指定 loader 放入 worker threads 中并行执行，被标记为 `parallel` 的 loader 会通过多线程调度运行，从而减少主线程的负担并提升构建性能。
+
+- 设置为 `true` 时，loader 会在 worker 中执行，并由 Rspack 自动选择合适的线程数量。
+- 设置为 `{ maxWorkers }` 时，可以手动控制最大 worker 的数量。
+- 设置为 `false` 或省略时，该 loader 默认会在主线程中执行。
+
+例如，将 `less-loader` 配置为并行执行：
 
 ```js title="rspack.config.mjs"
 export default {
@@ -2669,13 +2675,13 @@ export default {
 };
 ```
 
-对于当前 `Rule` 中有多个 loader 同时配置了 `Rule.use.parallel = true`，rspack 会在同个 worker 中执行所有 loader 任务，直到下一个没有标记 `parallel` 的 loader 或下一个 loader 为一个 Rust 的 `builtin:` loader。这样做可以提升 loader 的并行性能。
+当同一条 Rule 下有多个 loader 开启了 `parallel` 选项，Rspack 会在同一个 worker 中按顺序依次运行这些 loader，直到遇到未启用 parallel 的 loader 或 Rust 实现的 builtin loader。这样可以在保证 loader 顺序的前提下最大化并行效率。
 
-:::warning
+:::tip
 
-- 只有开启 [experiments.parallelLoader](/config/experiments#experimentsparallelloader) 时该配置才会生效。
-- loader 的配置需要满足 [HTML structured clone algorithm](https://nodejs.org/api/worker_threads.html#portpostmessagevalue-transferlist)，否则会发送失败。
-- 目前 Rspack 不支持大多数 `LoaderContext._compilation`, `LoaderContext._compiler`, `LoaderContext._module` 上的方法。
+- 由于当前功能是实验性特性，只有开启 [experiments.parallelLoader](/config/experiments#experimentsparallelloader) 时该配置才会生效。
+- loader 的选项需要满足 [HTML structured clone algorithm](https://nodejs.org/api/worker_threads.html#portpostmessagevalue-transferlist)，否则会发送失败。
+- 目前 loader 在 worker 中不支持 `LoaderContext._compilation`, `LoaderContext._compiler`, `LoaderContext._module` 上的大多数方法。
 
 :::