refactor(config): merge test config layers with Rstest

Author: chenjiahan

packages/rstack/src/rstestConfig.ts

@@ -1,6 +1,11 @@
 import type { ConfigParams } from '@rsbuild/core';
-import type { RstestConfig, RstestConfigExport } from '@rstest/core';
+import {
+  type RstestConfig,
+  type RstestConfigExport,
+  mergeRstestConfig,
+} from '@rstest/core';
 import { loadRstackConfig, type Configs } from './config.ts';
+import { resolveConfigLayers } from './configLayers.ts';
 
 const resolveAutomaticExtends = async (
   configs: Configs,
@@ -86,20 +91,18 @@ const extendsConfig = async (
   };
 };
 
-const resolveRstestConfig = async (configs: Configs) => {
-  const testConfig = configs.test;
-  if (!testConfig) {
-    return {};
-  }
-  if (typeof testConfig === 'function') {
-    return testConfig();
-  }
-  return testConfig;
+export const resolveRstestConfig = async (
+  layers: readonly Configs[],
+): Promise<RstestConfig> => {
+  const configs = await resolveConfigLayers(layers, 'test');
+  return configs.length > 1
+    ? mergeRstestConfig(...configs)
+    : (configs[0] ?? {});
 };
 
 const loadRstestConfig = (async (params: ConfigParams) => {
   const { configs } = await loadRstackConfig();
-  const testConfig = await resolveRstestConfig(configs);
+  const testConfig = await resolveRstestConfig([configs]);
   return extendsConfig(configs, testConfig, params);
 }) as RstestConfigExport;
 

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

@@ -0,0 +1,37 @@
+import { createRequire } from 'node:module';
+import { expect, test } from 'rstack/test';
+
+// Bypass Rstest's replacement of @rstest/core with its test runtime APIs.
+const { resolveRstestConfig } = createRequire(import.meta.url)(
+  '../../dist/rstestConfig.js',
+) as typeof import('../../src/rstestConfig.ts');
+
+test('merges test layers using native Rstest rules', async () => {
+  const config = await resolveRstestConfig([
+    {
+      test: {
+        extends: { testTimeout: 5000 },
+        retry: 1,
+        setupFiles: ['./base.ts'],
+        reporters: ['default'],
+        projects: ['./base.config.ts'],
+      },
+    },
+    {
+      test: {
+        retry: 2,
+        setupFiles: ['./project.ts'],
+        reporters: ['dot'],
+        projects: ['./project.config.ts'],
+      },
+    },
+  ]);
+
+  expect(config).toMatchObject({
+    extends: { testTimeout: 5000 },
+    retry: 2,
+    setupFiles: ['./base.ts', './project.ts'],
+    reporters: ['dot'],
+    projects: ['./base.config.ts', './project.config.ts'],
+  });
+});