feat: support for importModule in api.transform (#4217)

e2e/cases/plugin-api/plugin-transform-import-module/index.test.ts

@@ -0,0 +1,18 @@
+import { build, rspackOnlyTest } from '@e2e/helper';
+import { expect } from '@playwright/test';
+
+rspackOnlyTest(
+  'should allow plugin to transform code and call `importModule`',
+  async () => {
+    const rsbuild = await build({
+      cwd: __dirname,
+    });
+
+    const files = await rsbuild.unwrapOutputJSON();
+    const indexCss = Object.keys(files).find(
+      (file) => file.includes('index') && file.endsWith('.css'),
+    );
+
+    expect(files[indexCss!].includes('#00f')).toBeTruthy();
+  },
+);

e2e/cases/plugin-api/plugin-transform-import-module/myPlugin.ts

@@ -0,0 +1,13 @@
+import { join } from 'node:path';
+import type { RsbuildPlugin } from '@rsbuild/core';
+
+export const myPlugin: RsbuildPlugin = {
+  name: 'my-plugin',
+  setup(api) {
+    api.transform({ test: /\.css$/ }, async ({ code, importModule }) => {
+      // @ts-expect-error TODO: Rspack type issue
+      const { foo } = await importModule(join(__dirname, './src/foo.ts'));
+      return code.replace('red', foo);
+    });
+  },
+};

e2e/cases/plugin-api/plugin-transform-import-module/rsbuild.config.ts

@@ -0,0 +1,5 @@
+import { myPlugin } from './myPlugin';
+
+export default {
+  plugins: [myPlugin],
+};

e2e/cases/plugin-api/plugin-transform-import-module/src/foo.ts

@@ -0,0 +1 @@
+export const foo = 'blue';

e2e/cases/plugin-api/plugin-transform-import-module/src/index.css

@@ -0,0 +1,3 @@
+body {
+  color: red;
+}

e2e/cases/plugin-api/plugin-transform-import-module/src/index.js

@@ -0,0 +1,3 @@
+import './index.css';
+
+console.log('hello');

packages/core/src/loader/transformLoader.ts

@@ -1,5 +1,5 @@
 import type { LoaderContext } from '@rspack/core';
-import type { EnvironmentContext, Rspack, TransformContext } from '../types';
+import type { EnvironmentContext, Rspack } from '../types';
 
 export type TransformLoaderOptions = {
   id: string;
@@ -30,8 +30,9 @@ export default async function transform(
     resourcePath: this.resourcePath,
     resourceQuery: this.resourceQuery,
     environment: getEnvironment(),
-    addDependency: this.addDependency,
-    emitFile: this.emitFile as TransformContext['emitFile'],
+    addDependency: this.addDependency.bind(this),
+    emitFile: this.emitFile.bind(this),
+    importModule: this.importModule.bind(this),
   });
 
   if (result === null || result === undefined) {

packages/core/src/types/plugin.ts

@@ -263,12 +263,11 @@ export type TransformContext = {
    * @param sourceMap source map of the asset
    * @param assetInfo additional asset information
    */
-  emitFile: (
-    name: string,
-    content: string | Buffer,
-    sourceMap?: string,
-    assetInfo?: Record<string, any>,
-  ) => void;
+  emitFile: Rspack.LoaderContext['emitFile'];
+  /**
+   * Compile and execute a module at the build time.
+   */
+  importModule: Rspack.LoaderContext['importModule'];
 };
 
 export type TransformHandler = (