fix: return empty array instead of undefined and wrap async in array

vitePlugins() now returns [] when skipping, making it directly
assignable to plugins. For async callbacks, wrap in an array since
Vite's plugins field expects PluginOption[], not a bare Promise.

Author: fengmk2

docs/config/troubleshooting.md

@@ -22,10 +22,12 @@ For heavy plugins that should be lazily imported, combine with dynamic `import()
 import { defineConfig, vitePlugins } from 'vite-plus';
 
 export default defineConfig({
-  plugins: vitePlugins(async () => {
-    const { default: heavyPlugin } = await import('vite-plugin-heavy');
-    return [heavyPlugin()];
-  }),
+  plugins: [
+    vitePlugins(async () => {
+      const { default: heavyPlugin } = await import('vite-plugin-heavy');
+      return [heavyPlugin()];
+    }),
+  ],
 });
 ```
 

packages/cli/snap-tests/lazy-loading-plugins/vite.config.ts

@@ -1,8 +1,10 @@
 import { defineConfig, vitePlugins } from 'vite-plus';
 
 export default defineConfig({
-  plugins: vitePlugins(async () => {
-    const { default: myLazyPlugin } = await import('./my-plugin');
-    return [myLazyPlugin()];
-  }),
+  plugins: [
+    vitePlugins(async () => {
+      const { default: myLazyPlugin } = await import('./my-plugin');
+      return [myLazyPlugin()];
+    }),
+  ],
 });

packages/cli/src/__tests__/index.spec.ts

@@ -36,16 +36,16 @@ test('should keep vitest exports stable', () => {
   expect(defaultBrowserPort).toBeDefined();
 });
 
-test('vitePlugins returns undefined when VP_COMMAND is unset', () => {
+test('vitePlugins returns empty array when VP_COMMAND is unset', () => {
   delete process.env.VP_COMMAND;
   const result = vitePlugins(() => [{ name: 'test' }]);
-  expect(result).toBeUndefined();
+  expect(result).toEqual([]);
 });
 
-test('vitePlugins returns undefined when VP_COMMAND is empty string', () => {
+test('vitePlugins returns empty array when VP_COMMAND is empty string', () => {
   process.env.VP_COMMAND = '';
   const result = vitePlugins(() => [{ name: 'test' }]);
-  expect(result).toBeUndefined();
+  expect(result).toEqual([]);
 });
 
 test.each(['dev', 'build', 'test', 'preview'])(
@@ -58,11 +58,11 @@ test.each(['dev', 'build', 'test', 'preview'])(
 );
 
 test.each(['lint', 'fmt', 'check', 'pack', 'install', 'run'])(
-  'vitePlugins returns undefined when VP_COMMAND is %s',
+  'vitePlugins returns empty array when VP_COMMAND is %s',
   (cmd) => {
     process.env.VP_COMMAND = cmd;
     const result = vitePlugins(() => [{ name: 'my-plugin' }]);
-    expect(result).toBeUndefined();
+    expect(result).toEqual([]);
   },
 );
 
@@ -76,10 +76,10 @@ test('vitePlugins supports async callback', async () => {
   expect(await result).toEqual([{ name: 'async-plugin' }]);
 });
 
-test('vitePlugins returns undefined for async callback when skipped', () => {
+test('vitePlugins returns empty array for async callback when skipped', () => {
   process.env.VP_COMMAND = 'lint';
   const result = vitePlugins(async () => {
     return [{ name: 'async-plugin' }];
   });
-  expect(result).toBeUndefined();
+  expect(result).toEqual([]);
 });

packages/cli/src/define-config.ts

@@ -47,10 +47,10 @@ export function defineConfig(config: ViteUserConfigExport): ViteUserConfigExport
   return viteDefineConfig(config);
 }
 
-export function vitePlugins<T>(cb: () => T): T | undefined {
+export function vitePlugins<T>(cb: () => T): T | [] {
   const cmd = process.env.VP_COMMAND;
   if (cmd === 'dev' || cmd === 'build' || cmd === 'test' || cmd === 'preview') {
     return cb();
   }
-  return undefined;
+  return [];
 }