fix: fix external: true merging (#21164)

Author: hi-ogawa

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

@@ -166,21 +166,24 @@ describe('mergeConfig', () => {
   })
 
   test('handles ssr.noExternal', () => {
-    const baseConfig = {
+    const baseConfig: UserConfig = {
       ssr: {
         noExternal: true,
+        external: true,
       },
     }
 
-    const newConfig = {
+    const newConfig: UserConfig = {
       ssr: {
         noExternal: ['foo'],
+        external: ['bar'],
       },
     }
 
-    const mergedConfig = {
+    const mergedConfig: UserConfig = {
       ssr: {
         noExternal: true,
+        external: true,
       },
     }
 

packages/vite/src/node/utils.ts

@@ -1260,7 +1260,7 @@ function mergeConfigRecursively(
       merged[key] = [].concat(existing, value)
       continue
     } else if (
-      ((key === 'noExternal' &&
+      (((key === 'noExternal' || key === 'external') &&
         (rootPath === 'ssr' || rootPath === 'resolve')) ||
         (key === 'allowedHosts' && rootPath === 'server')) &&
       (existing === true || value === true)