fix(entry): allow empty entry when module federation is used

e2e/cases/module-federation/v1-without-entry/index.test.ts

@@ -0,0 +1,9 @@
+import { expect, rspackTest } from '@e2e/helper';
+
+rspackTest('should start MF app in dev without entry', async ({ devOnly }) => {
+  await expect(devOnly()).resolves.toBeTruthy();
+});
+
+rspackTest('should build MF app without entry', async ({ build }) => {
+  await expect(build()).resolves.toBeTruthy();
+});

e2e/cases/module-federation/v1-without-entry/rsbuild.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig } from '@rsbuild/core';
+import { pluginReact } from '@rsbuild/plugin-react';
+
+export default defineConfig({
+  plugins: [pluginReact()],
+  moduleFederation: {
+    options: {
+      name: 'remote',
+      exposes: {
+        './Button': './src/Button',
+      },
+      filename: 'remoteEntry.js',
+      shared: {
+        react: {
+          singleton: true,
+          requiredVersion: '^19.0.0',
+        },
+        'react-dom': {
+          singleton: true,
+          requiredVersion: '^19.0.0',
+        },
+      },
+    },
+  },
+});

e2e/cases/module-federation/v1-without-entry/src/Button.jsx

@@ -0,0 +1,5 @@
+export const Button = () => (
+  <button type="button" id="button">
+    Button
+  </button>
+);

e2e/cases/module-federation/v2-without-entry/index.test.ts

@@ -0,0 +1,9 @@
+import { expect, rspackTest } from '@e2e/helper';
+
+rspackTest('should start MF app in dev without entry', async ({ devOnly }) => {
+  await expect(devOnly()).resolves.toBeTruthy();
+});
+
+rspackTest('should build MF app without entry', async ({ build }) => {
+  await expect(build()).resolves.toBeTruthy();
+});

e2e/cases/module-federation/v2-without-entry/rsbuild.config.ts

@@ -0,0 +1,16 @@
+import { pluginModuleFederation } from '@module-federation/rsbuild-plugin';
+import { defineConfig } from '@rsbuild/core';
+import { pluginReact } from '@rsbuild/plugin-react';
+
+export default defineConfig({
+  plugins: [
+    pluginReact(),
+    pluginModuleFederation({
+      name: 'remote',
+      exposes: {
+        './Button': './src/Button',
+      },
+      shared: ['react', 'react-dom'],
+    }),
+  ],
+});

e2e/cases/module-federation/v2-without-entry/src/Button.jsx

@@ -0,0 +1,5 @@
+export const Button = () => (
+  <button type="button" id="button">
+    Button
+  </button>
+);

packages/core/src/plugins/entry.ts

@@ -1,5 +1,5 @@
-import { castArray, color, createVirtualModule } from '../helpers';
-import type { RsbuildEntryDescription, RsbuildPlugin } from '../types';
+import { castArray, color, createVirtualModule, isObject } from '../helpers';
+import type { RsbuildEntryDescription, RsbuildPlugin, Rspack } from '../types';
 
 export const pluginEntry = (): RsbuildPlugin => ({
   name: 'rsbuild:entry',
@@ -32,16 +32,39 @@ export const pluginEntry = (): RsbuildPlugin => ({
       }
     });
 
-    api.onBeforeCreateCompiler(({ bundlerConfigs }) => {
-      if (bundlerConfigs.every((config) => !config.entry)) {
+    // Check missing entry config
+    api.onBeforeCreateCompiler({
+      order: 'post',
+      handler: ({ bundlerConfigs }) => {
+        const hasEntry = bundlerConfigs.some((config) => config.entry);
+        if (hasEntry) {
+          return;
+        }
+
+        const isModuleFederationPlugin = (plugin: Rspack.Plugin) =>
+          isObject(plugin) &&
+          plugin.constructor.name === 'ModuleFederationPlugin';
+
+        const hasModuleFederation = bundlerConfigs.some(({ plugins }) =>
+          plugins?.some(isModuleFederationPlugin),
+        );
+
+        // Allow entry to be left empty when module federation is enabled
+        if (hasModuleFederation) {
+          bundlerConfigs.forEach((config) => {
+            config.entry = {};
+          });
+          return;
+        }
+
         throw new Error(
           `${color.dim('[rsbuild:config]')} Could not find any entry module, please make sure that ${color.yellow(
             'src/index.(ts|js|tsx|jsx|mts|cts|mjs|cjs)',
           )} exists, or customize entry through the ${color.yellow(
             'source.entry',
           )} configuration.`,
         );
-      }
+      },
     });
   },
 });