feat: add alias option

docs/.vitepress/components.d.ts

@@ -1,6 +1,6 @@
 // generated by unplugin-vue-components
 // We suggest you to commit this file into source control
-// Read more: https://github.com/vuejs/vue-next/pull/3399
+// Read more: https://github.com/vuejs/core/pull/3399
 import '@vue/runtime-core'
 
 declare module '@vue/runtime-core' {

docs/config/index.md

@@ -109,6 +109,12 @@ This might potentially cause some misalignment if a package has different logic
 
 Interpret CJS module's default as named exports.
 
+### alias
+
+- **Type:** `Record<string, string> | Array<{ find: string | RegExp, replacement: string, customResolver?: ResolverFunction | ResolverObject }>`
+
+Define custom aliases when running inside tests. They will be merged with aliases from `resolve.alias`.
+
 ### globals
 
 - **Type:** `boolean`

packages/vite-node/src/externalize.ts

@@ -8,7 +8,7 @@ const ESM_FOLDER_RE = /\/esm\/(.*\.js)$/
 
 const defaultInline = [
   /virtual:/,
-  /\.ts$/,
+  /\.[mc]?ts$/,
 ]
 
 const depsExternal = [

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

@@ -75,6 +75,7 @@ export async function VitestPlugin(options: UserConfig = {}, ctx = new Vitest())
             // 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: preOptions.alias,
           },
           server: {
             ...preOptions.api,
@@ -101,6 +102,9 @@ export async function VitestPlugin(options: UserConfig = {}, ctx = new Vitest())
         if (viteConfigTest.watch === false)
           viteConfigTest.run = true
 
+        if ('alias' in viteConfigTest)
+          delete viteConfigTest.alias
+
         // viteConfig.test is final now, merge it for real
         options = deepMerge(
           {},

packages/vitest/src/runtime/error.ts

@@ -81,7 +81,7 @@ export function processError(err: any) {
     if (typeof err.message === 'string')
       err.message = normalizeErrorMessage(err.message)
 
-    if (typeof err.cause === 'object' && err.cause.message === 'string')
+    if (typeof err.cause === 'object' && typeof err.cause.message === 'string')
       err.cause.message = normalizeErrorMessage(err.cause.message)
   }
   catch {}

packages/vitest/src/types/config.ts

@@ -1,4 +1,4 @@
-import type { CommonServerOptions } from 'vite'
+import type { AliasOptions, CommonServerOptions } from 'vite'
 import type { PrettyFormatOptions } from 'pretty-format'
 import type { FakeTimerInstallOpts } from '@sinonjs/fake-timers'
 import type { BuiltinReporters } from '../node/reporters'
@@ -393,6 +393,13 @@ export interface InlineConfig {
      */
     seed?: number
   }
+
+  /**
+   * Specifies an `Object`, or an `Array` of `Object`,
+   * which defines aliases used to replace values in `import` or `require` statements.
+   * Will be merged with the default aliases inside `resolve.alias`.
+   */
+  alias?: AliasOptions
 }
 
 export interface UserConfig extends InlineConfig {

test/core/src/aliased-mod.ts

@@ -0,0 +1 @@
+export const isAliased = true

test/core/test/alias.test.ts

@@ -0,0 +1,7 @@
+// @ts-expect-error aliased to ../src/aliased-mod.ts
+import { isAliased } from 'test-alias'
+import { expect, test } from 'vitest'
+
+test('check that test.alias works', () => {
+  expect(isAliased).toBe(true)
+})

test/core/vitest.config.ts

@@ -56,5 +56,13 @@ export default defineConfig({
     sequence: {
       seed: 101,
     },
+    alias: [
+      {
+        find: 'test-alias',
+        replacement: '',
+        // vitest doesn't crash because function is defined
+        customResolver: () => resolve(__dirname, 'src', 'aliased-mod.ts'),
+      },
+    ],
   },
 })