fix(vite6): re-apply default conditions if using vite 6 or later

Vite 6 no longer applies default conditions when you override resolve.conditions.
This PR adds them back conditionally based on the vite version.

Fixes #7070

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

@@ -0,0 +1,16 @@
+import * as vite from 'vite'
+
+type Vite6Options = typeof vite & Partial<{
+  defaultServerConditions?: string[]
+}>
+
+/**
+ * In Vite 6+, providing a value for resolve.conditions overrides the defaults
+ * In Vite 5, passing ["node"] will be merged with the defaults
+ *
+ * @returns the appropriate conditions array depending on the vite version
+ *
+ */
+export function getDefaultServerConditions() {
+  return (vite as Vite6Options).defaultServerConditions ?? ['node']
+}

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

@@ -12,6 +12,7 @@ import { generateScopedClassName } from '../../integrations/css/css-modules'
 import { resolveApiServerConfig } from '../config/resolveConfig'
 import { Vitest } from '../core'
 import { createViteLogger, silenceImportViteIgnoreWarning } from '../viteLogger'
+import { getDefaultServerConditions } from './conditions'
 import { CoverageTransform } from './coverageTransform'
 import { CSSEnablerPlugin } from './cssEnabler'
 import { MocksPlugins } from './mocks'
@@ -73,6 +74,8 @@ export async function VitestPlugin(
           open = testConfig.uiBase ?? '/__vitest__/'
         }
 
+        const conditions = getDefaultServerConditions()
+
         const config: ViteConfig = {
           root: viteConfig.test?.root || options.root,
           esbuild:
@@ -90,7 +93,7 @@ export async function VitestPlugin(
             // setting this option can bypass that and fallback to cjs version
             mainFields: [],
             alias: testConfig.alias,
-            conditions: ['node'],
+            conditions,
           },
           server: {
             ...testConfig.api,
@@ -119,7 +122,7 @@ export async function VitestPlugin(
                 // by default Vite resolves `module` field, which not always a native ESM module
                 // setting this option can bypass that and fallback to cjs version
                 mainFields: [],
-                conditions: ['node'],
+                conditions,
               },
             },
           },

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

@@ -7,6 +7,7 @@ import { basename, dirname, relative, resolve } from 'pathe'
 import { configDefaults } from '../../defaults'
 import { generateScopedClassName } from '../../integrations/css/css-modules'
 import { createViteLogger, silenceImportViteIgnoreWarning } from '../viteLogger'
+import { getDefaultServerConditions } from './conditions'
 import { CoverageTransform } from './coverageTransform'
 import { CSSEnablerPlugin } from './cssEnabler'
 import { MocksPlugins } from './mocks'
@@ -62,14 +63,16 @@ export function WorkspaceVitestPlugin(
           }
         }
 
+        const conditions = getDefaultServerConditions()
+
         const config: ViteConfig = {
           root,
           resolve: {
             // by default Vite resolves `module` field, which not always a native ESM module
             // setting this option can bypass that and fallback to cjs version
             mainFields: [],
             alias: testConfig.alias,
-            conditions: ['node'],
+            conditions,
           },
           esbuild: viteConfig.esbuild === false
             ? false
@@ -104,7 +107,7 @@ export function WorkspaceVitestPlugin(
                 // by default Vite resolves `module` field, which not always a native ESM module
                 // setting this option can bypass that and fallback to cjs version
                 mainFields: [],
-                conditions: ['node'],
+                conditions,
               },
             },
           },