feat: support custom postcss options

src/TailwindCSSRspackPlugin.ts

@@ -4,7 +4,7 @@ import { tmpdir } from 'node:os';
 import path from 'node:path';
 import { pathToFileURL } from 'node:url';
 
-import type { Rspack } from '@rsbuild/core';
+import type { PostCSSLoaderOptions, Rspack } from '@rsbuild/core';
 
 /**
  * The options for {@link TailwindRspackPlugin}.
@@ -15,10 +15,6 @@ interface TailwindRspackPluginOptions {
   /**
    * The path to the configuration of Tailwind CSS.
    *
-   * @remarks
-   *
-   * The default value is `tailwind.config.js`.
-   *
    * @example
    *
    * Use absolute path:
@@ -58,7 +54,36 @@ interface TailwindRspackPluginOptions {
    * }
    * ```
    */
-  config?: string;
+  config: string;
+
+  /**
+   * The postcss options to be applied.
+   *
+   * @example
+   *
+   * Use `cssnano`:
+   *
+   * ```js
+   * // rspack.config.js
+   * import { TailwindRspackPlugin } from '@rsbuild/plugin-tailwindcss'
+   *
+   * export default {
+   *   plugins: [
+   *     new TailwindRspackPlugin({
+   *       postcssOptions: {
+   *         plugins: {
+   *           cssnano: process.env['NODE_ENV'] === 'production' ? {} : false,
+   *         },
+   *       },
+   *     }),
+   *   ],
+   * }
+   * ```
+   */
+  postcssOptions: Exclude<
+    PostCSSLoaderOptions['postcssOptions'],
+    (loaderContext: Rspack.LoaderContext) => void
+  >;
 }
 
 /**
@@ -67,9 +92,7 @@ interface TailwindRspackPluginOptions {
  * @public
  */
 class TailwindRspackPlugin {
-  constructor(
-    private readonly options?: TailwindRspackPluginOptions | undefined,
-  ) {}
+  constructor(private readonly options: TailwindRspackPluginOptions) {}
 
   /**
    * `defaultOptions` is the default options that the {@link TailwindRspackPlugin} uses.
@@ -79,33 +102,27 @@ class TailwindRspackPlugin {
   static defaultOptions: Readonly<Required<TailwindRspackPluginOptions>> =
     Object.freeze<Required<TailwindRspackPluginOptions>>({
       config: 'tailwind.config.js',
+      postcssOptions: {},
     });
 
   /**
    * The entry point of a Rspack plugin.
    * @param compiler - the Rspack compiler
    */
   apply(compiler: Rspack.Compiler): void {
-    new TailwindRspackPluginImpl(
-      compiler,
-      Object.assign({}, TailwindRspackPlugin.defaultOptions, this.options),
-    );
+    new TailwindRspackPluginImpl(compiler, this.options);
   }
 }
 
 export { TailwindRspackPlugin };
 export type { TailwindRspackPluginOptions };
 
-type NoUndefinedField<T> = {
-  [P in keyof T]-?: NoUndefinedField<NonNullable<T[P]>>;
-};
-
 class TailwindRspackPluginImpl {
   name = 'TailwindRspackPlugin';
 
   constructor(
     private compiler: Rspack.Compiler,
-    private options: NoUndefinedField<TailwindRspackPluginOptions>,
+    private options: TailwindRspackPluginOptions,
   ) {
     const { RawSource } = compiler.webpack.sources;
     compiler.hooks.thisCompilation.tap(this.name, (compilation) => {
@@ -146,6 +163,7 @@ class TailwindRspackPluginImpl {
               ]);
 
               const postcssTransform = postcss([
+                ...(options.postcssOptions?.plugins ?? []),
                 // We use a config path to avoid performance issue of TailwindCSS
                 // See: https://github.com/tailwindlabs/tailwindcss/issues/14229
                 tailwindcss({
@@ -161,7 +179,7 @@ class TailwindRspackPluginImpl {
                   // FIXME: add custom postcss config
                   const transformResult = await postcssTransform.process(
                     content,
-                    { from: asset.name },
+                    { from: asset.name, ...options.postcssOptions },
                   );
                   // FIXME: add sourcemap support
                   compilation.updateAsset(

src/index.ts

@@ -1,4 +1,8 @@
-import type { RsbuildPlugin } from '@rsbuild/core';
+import type {
+  PostCSSLoaderOptions,
+  RsbuildPlugin,
+  Rspack,
+} from '@rsbuild/core';
 
 import { TailwindRspackPlugin } from './TailwindCSSRspackPlugin.js';
 
@@ -58,13 +62,45 @@ export const pluginTailwindCSS = (
   name: 'rsbuild:tailwindcss',
 
   setup(api) {
+    let postcssOptions: Exclude<
+      PostCSSLoaderOptions['postcssOptions'],
+      (loaderContext: Rspack.LoaderContext) => void
+    >;
+
+    api.modifyRsbuildConfig({
+      order: 'post',
+      handler(config, { mergeRsbuildConfig }) {
+        return mergeRsbuildConfig(config, {
+          tools: {
+            postcss(config) {
+              if (typeof config.postcssOptions === 'function') {
+                throw new Error(
+                  'pluginTailwindCSS does not support using `tools.postcss` as function',
+                );
+              }
+              if (config.postcssOptions) {
+                // Remove `tailwindcss` from `postcssOptions`
+                // to avoid `@tailwind` being transformed by `postcss-loader`.
+                config.postcssOptions.plugins =
+                  config.postcssOptions.plugins?.filter(
+                    (p) =>
+                      'postcssPlugin' in p && p.postcssPlugin !== 'tailwindcss',
+                  ) ?? [];
+                postcssOptions = config.postcssOptions;
+              }
+            },
+          },
+        });
+      },
+    });
+
     api.modifyBundlerChain({
       order: 'post',
       handler(chain) {
         chain
           .plugin('tailwindcss')
           .use(TailwindRspackPlugin, [
-            { config: options.config ?? 'tailwind.config.js' },
+            { config: options.config ?? 'tailwind.config.js', postcssOptions },
           ]);
       },
     });

test/postcss-config/flex-to-grid.js

@@ -0,0 +1,15 @@
+/**
+ * @returns {import('postcss').AcceptedPlugin}
+ */
+export default function () {
+  return {
+    postcssPlugin: 'flex-to-grid',
+    Declaration: {
+      display(decl) {
+        if (decl.value === 'flex') {
+          decl.value = 'grid';
+        }
+      },
+    },
+  };
+}

test/postcss-config/index.test.ts

@@ -0,0 +1,35 @@
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { expect, test } from '@playwright/test';
+import { createRsbuild } from '@rsbuild/core';
+import { pluginTailwindCSS } from '../../src';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+test('should build with postcss.config.js', async ({ page }) => {
+  const rsbuild = await createRsbuild({
+    cwd: __dirname,
+    rsbuildConfig: {
+      plugins: [pluginTailwindCSS()],
+    },
+  });
+
+  await rsbuild.build();
+  const { server, urls } = await rsbuild.preview();
+
+  await page.goto(urls[0]);
+
+  const display = await page.evaluate(() => {
+    const el = document.getElementById('test');
+
+    if (!el) {
+      throw new Error('#test not found');
+    }
+
+    return window.getComputedStyle(el).getPropertyValue('display');
+  });
+
+  expect(display).toBe('grid');
+
+  await server.close();
+});

test/postcss-config/postcss.config.js

@@ -0,0 +1,6 @@
+import tailwindcss from 'tailwindcss';
+import flexToGrid from './flex-to-grid';
+
+export default {
+  plugins: [tailwindcss(), flexToGrid()],
+};

test/postcss-config/src/index.js

@@ -0,0 +1,11 @@
+import 'tailwindcss/utilities.css';
+
+function className() {
+  return 'flex';
+}
+
+const root = document.getElementById('root');
+const element = document.createElement('div');
+element.id = 'test';
+element.className = className();
+root.appendChild(element);

test/tools-postcss/flex-to-grid.js

@@ -0,0 +1,15 @@
+/**
+ * @returns {import('postcss').AcceptedPlugin}
+ */
+export default function () {
+  return {
+    postcssPlugin: 'flex-to-grid',
+    Declaration: {
+      display(decl) {
+        if (decl.value === 'flex') {
+          decl.value = 'grid';
+        }
+      },
+    },
+  };
+}

test/tools-postcss/index.test.ts

@@ -0,0 +1,80 @@
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { expect, test } from '@playwright/test';
+import { createRsbuild } from '@rsbuild/core';
+import { pluginTailwindCSS } from '../../src';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+test('should build with tools.postcss with tailwindcss', async ({ page }) => {
+  const { default: tailwindcss } = await import('tailwindcss');
+  const rsbuild = await createRsbuild({
+    cwd: __dirname,
+    rsbuildConfig: {
+      plugins: [pluginTailwindCSS()],
+      tools: {
+        postcss: {
+          postcssOptions: {
+            plugins: [tailwindcss()],
+          },
+        },
+      },
+    },
+  });
+
+  await rsbuild.build();
+  const { server, urls } = await rsbuild.preview();
+
+  await page.goto(urls[0]);
+
+  const display = await page.evaluate(() => {
+    const el = document.getElementById('test');
+
+    if (!el) {
+      throw new Error('#test not found');
+    }
+
+    return window.getComputedStyle(el).getPropertyValue('display');
+  });
+
+  expect(display).toBe('flex');
+
+  await server.close();
+});
+
+test('should build with tools.postcss with custom plugin', async ({ page }) => {
+  const { default: tailwindcss } = await import('tailwindcss');
+  const { default: flexToGrid } = await import('./flex-to-grid.js');
+  const rsbuild = await createRsbuild({
+    cwd: __dirname,
+    rsbuildConfig: {
+      plugins: [pluginTailwindCSS()],
+      tools: {
+        postcss: {
+          postcssOptions: {
+            plugins: [flexToGrid()],
+          },
+        },
+      },
+    },
+  });
+
+  await rsbuild.build();
+  const { server, urls } = await rsbuild.preview();
+
+  await page.goto(urls[0]);
+
+  const display = await page.evaluate(() => {
+    const el = document.getElementById('test');
+
+    if (!el) {
+      throw new Error('#test not found');
+    }
+
+    return window.getComputedStyle(el).getPropertyValue('display');
+  });
+
+  expect(display).toBe('grid');
+
+  await server.close();
+});

test/tools-postcss/src/index.js

@@ -0,0 +1,11 @@
+import 'tailwindcss/utilities.css';
+
+function className() {
+  return 'flex';
+}
+
+const root = document.getElementById('root');
+const element = document.createElement('div');
+element.id = 'test';
+element.className = className();
+root.appendChild(element);