refactor(config): merge doc config layers with Rspress

packages/rstack/src/rspressConfig.ts

@@ -1,21 +1,23 @@
 import type { WatchFiles } from '@rsbuild/core';
 import type { UserConfig } from '@rspress/core';
 import { loadRstackConfig, type Configs } from './config.ts';
+import { resolveConfigLayers } from './configLayers.ts';
 
-const resolveRspressConfig = async (configs: Configs): Promise<UserConfig> => {
-  const docConfig = configs.doc;
-  if (!docConfig) {
-    return {};
+export const resolveRspressConfig = async (
+  layers: readonly Configs[],
+): Promise<UserConfig> => {
+  const configs = await resolveConfigLayers(layers, 'doc');
+  if (configs.length <= 1) {
+    return configs[0] ?? {};
   }
-  if (typeof docConfig === 'function') {
-    return docConfig();
-  }
-  return docConfig;
+
+  const { mergeDocConfig } = await import('@rspress/core');
+  return mergeDocConfig(...configs);
 };
 
 export default async (): Promise<UserConfig> => {
   const { configs, filePath, dependencies } = await loadRstackConfig();
-  const config = await resolveRspressConfig(configs);
+  const config = await resolveRspressConfig([configs]);
 
   if (!filePath) {
     return config;

packages/rstack/tests/config/doc-merge.test.ts

@@ -0,0 +1,43 @@
+import { expect, test } from 'rstack/test';
+import { resolveRspressConfig } from '../../src/rspressConfig.ts';
+
+test('merges doc layers using native Rspress rules', async () => {
+  const sharedRspack = () => ({ name: 'shared' });
+  const projectRspack = () => ({ name: 'project' });
+  const config = await resolveRspressConfig([
+    {
+      doc: {
+        title: 'Shared',
+        plugins: [{ name: 'shared-plugin' }],
+        builderConfig: {
+          source: { define: { SHARED: true, ENV: 'base' } },
+          dev: { watchFiles: [{ paths: ['./shared.md'] }] },
+          tools: { rspack: sharedRspack },
+        },
+      },
+    },
+    {
+      doc: {
+        title: 'Project',
+        plugins: [{ name: 'project-plugin' }],
+        builderConfig: {
+          source: { define: { ENV: 'production' } },
+          dev: { watchFiles: [{ paths: ['./project.md'] }] },
+          tools: { rspack: projectRspack },
+        },
+      },
+    },
+  ]);
+
+  expect(config).toEqual({
+    title: 'Project',
+    plugins: [{ name: 'shared-plugin' }, { name: 'project-plugin' }],
+    builderConfig: {
+      source: { define: { SHARED: true, ENV: 'production' } },
+      dev: {
+        watchFiles: [{ paths: ['./shared.md'] }, { paths: ['./project.md'] }],
+      },
+      tools: { rspack: projectRspack },
+    },
+  });
+});