fix: do not throw when importing a type from an external package

packages/vitest/src/runtime/moduleRunner/moduleRunner.ts

@@ -87,6 +87,17 @@ export class VitestModuleRunner extends viteModuleRunner.ModuleRunner {
     }
   }
 
+  /**
+   * Vite checks that the module has exports emulating the Node.js behaviour,
+   * but Vitest is more relaxed.
+   *
+   * We should keep the Vite behavour when there is a `strict` flag.
+   * @internal
+   */
+  processImport(exports: Record<string, any>): Record<string, any> {
+    return exports
+  }
+
   public async import(rawId: string): Promise<any> {
     const resolved = await this.vitestOptions.transport.resolveId(rawId)
     return super.import(resolved ? resolved.url : rawId)

test/core/deps/dep-esm-non-existing/index.mts

@@ -0,0 +1 @@
+export type NonExported = true

test/core/deps/dep-esm-non-existing/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@test/dep-esm-non-existing",
+  "type": "module",
+  "main": "./index.mjs"
+}

test/core/package.json

@@ -14,6 +14,7 @@
   },
   "devDependencies": {
     "@standard-schema/spec": "^1.0.0",
+    "@test/dep-esm-non-existing": "link:./deps/dep-esm-non-existing",
     "@test/vite-environment-external": "link:./projects/vite-environment-external",
     "@test/vite-external": "link:./projects/vite-external",
     "@types/debug": "catalog:",

test/core/test/imports.test.ts

@@ -1,12 +1,18 @@
 import { mkdir, writeFile } from 'node:fs/promises'
 import { fileURLToPath } from 'node:url'
+import { NonExported } from '@test/dep-esm-non-existing'
 import { resolve } from 'pathe'
 import { describe, expect, test, vi } from 'vitest'
 // @ts-expect-error module is not typed
 import promiseExport from '../src/cjs/promise-export'
 
 import { dynamicRelativeImport } from '../src/relative-import'
 
+test('can import type from an ESM dependency', () => {
+  // @ts-expect-error NonExported is type
+  expect(NonExported).toBe(undefined)
+})
+
 test('promise export works correctly', async () => {
   await expect(promiseExport).resolves.toEqual({ value: 42 })
 })

test/core/vite.config.ts

@@ -91,6 +91,7 @@ export default defineConfig({
           /packages\/web-worker/,
           /\.wasm$/,
           /\/wasm-bindgen-no-cyclic\/index_bg.js/,
+          /dep-esm-non-existing/,
         ],
         inline: ['inline-lib'],
       },