fix: merge server.allowedHosts: true correctly (vitejs#20138)

Author: sapphi-red

packages/vite/src/node/__tests__/config.spec.ts

@@ -237,6 +237,22 @@ describe('mergeConfig', () => {
     expect(mergedConfig.server.hmr.server).toBe(httpServer)
   })
 
+  test('handles server.allowedHosts', () => {
+    const baseConfig = {
+      server: { allowedHosts: ['example.com'] },
+    }
+
+    const newConfig = {
+      server: { allowedHosts: true },
+    }
+
+    const mergedConfig = {
+      server: { allowedHosts: true },
+    }
+
+    expect(mergeConfig(baseConfig, newConfig)).toEqual(mergedConfig)
+  })
+
   test('throws error with functions', () => {
     const baseConfig = defineConfig(() => ({ base: 'base' }))
     const newConfig = defineConfig(() => ({ base: 'new' }))

packages/vite/src/node/utils.ts

@@ -1249,8 +1249,9 @@ function mergeConfigRecursively(
       merged[key] = [].concat(existing, value)
       continue
     } else if (
-      key === 'noExternal' &&
-      (rootPath === 'ssr' || rootPath === 'resolve') &&
+      ((key === 'noExternal' &&
+        (rootPath === 'ssr' || rootPath === 'resolve')) ||
+        (key === 'allowedHosts' && rootPath === 'server')) &&
       (existing === true || value === true)
     ) {
       merged[key] = true