fix: replace default ssr environment runner with Vitest server module runner (#9506)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: hi-ogawa

packages/vitest/src/node/core.ts

@@ -20,6 +20,7 @@ import { getTasks, hasFailed, limitConcurrency } from '@vitest/runner/utils'
 import { SnapshotManager } from '@vitest/snapshot/manager'
 import { deepClone, deepMerge, nanoid, noop, toArray } from '@vitest/utils/helpers'
 import { join, normalize, relative } from 'pathe'
+import { isRunnableDevEnvironment } from 'vite'
 import { version } from '../../package.json' with { type: 'json' }
 import { WebSocketReporter } from '../api/setup'
 import { distDir } from '../paths'
@@ -247,6 +248,21 @@ export class Vitest {
           this._fetcher,
           resolved,
         )
+    // patch default ssr runnable environment so third-party usage of `runner.import`
+    // still works with Vite's external/noExternal configuration.
+    const ssrEnvironment = server.environments.ssr
+    if (isRunnableDevEnvironment(ssrEnvironment)) {
+      const ssrRunner = new ServerModuleRunner(
+        ssrEnvironment,
+        this._fetcher,
+        resolved,
+      )
+      Object.defineProperty(ssrEnvironment, 'runner', {
+        value: ssrRunner,
+        writable: true,
+        configurable: true,
+      })
+    }
 
     if (this.config.watch) {
       // hijack server restart

packages/vitest/src/node/plugins/index.ts

@@ -260,8 +260,6 @@ export async function VitestPlugin(
         }
       },
       configureServer: {
-        // runs after vite:import-analysis as it relies on `server` instance on Vite 5
-        order: 'post',
         async handler(server) {
           if (options.watch && process.env.VITE_TEST_WATCHER_DEBUG) {
             server.watcher.on('ready', () => {

packages/vitest/src/node/plugins/workspace.ts

@@ -242,7 +242,6 @@ export function WorkspaceVitestPlugin(
     },
     {
       name: 'vitest:project:server',
-      enforce: 'post',
       async configureServer(server) {
         const options = deepMerge({}, configDefaults, server.config.test || {})
         await project._configureServer(options, server)

packages/vitest/src/node/project.ts

@@ -23,6 +23,7 @@ import { deepMerge, nanoid, slash } from '@vitest/utils/helpers'
 import { isAbsolute, join, relative } from 'pathe'
 import pm from 'picomatch'
 import { glob } from 'tinyglobby'
+import { isRunnableDevEnvironment } from 'vite'
 import { setup } from '../api/setup'
 import { createDefinesScript } from '../utils/config-helpers'
 import { NativeModuleRunner } from '../utils/nativeModuleRunner'
@@ -579,6 +580,20 @@ export class TestProject {
           this._fetcher,
           this._config,
         )
+
+    const ssrEnvironment = server.environments.ssr
+    if (isRunnableDevEnvironment(ssrEnvironment)) {
+      const ssrRunner = new ServerModuleRunner(
+        ssrEnvironment,
+        this._fetcher,
+        this._config,
+      )
+      Object.defineProperty(ssrEnvironment, 'runner', {
+        value: ssrRunner,
+        writable: true,
+        configurable: true,
+      })
+    }
   }
 
   /** @internal */

test/cli/fixtures/ssr-runner/basic.test.ts

@@ -0,0 +1,5 @@
+import { test, expect } from 'vitest'
+
+test('basic', () => {
+  expect(1 + 1).toBe(2)
+})

test/cli/fixtures/ssr-runner/test-runner.js

@@ -0,0 +1,2 @@
+import * as vite from 'vite'
+export default vite

test/cli/fixtures/ssr-runner/vitest.config.ts

@@ -0,0 +1,21 @@
+import assert from 'node:assert'
+import { isRunnableDevEnvironment, createServer } from 'vite'
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  plugins: [
+    {
+      name: 'test-ssr-runner',
+      // test ssr runner.import() with correct external semantics in configureServer hook
+      // vite should be externalized and reference-equal to the directly imported one
+      async configureServer(server) {
+        const ssr = server.environments.ssr
+        if (isRunnableDevEnvironment(ssr)) {
+          const m = await ssr.runner.import<{ default: typeof import("vite") }>('./test-runner.js')
+          assert(m.default.createServer === createServer)
+          ;(globalThis as any).__testSsrRunner = m.default.version
+        }
+      },
+    },
+  ],
+})

test/cli/test/ssr-runner.test.ts

@@ -0,0 +1,9 @@
+import { version } from 'vite'
+import { expect, it } from 'vitest'
+import { runVitest } from '../../test-utils'
+
+// https://github.com/vitest-dev/vitest/issues/9324
+it('ssr runner.import() works in configureServer', async () => {
+  await runVitest({ root: './fixtures/ssr-runner' })
+  expect((globalThis as any).__testSsrRunner).toBe(version)
+})