fix(mocker): support mocking builtins without node: prefix (#8829)

Author: sheremet-va

packages/vitest/src/node/pools/rpc.ts

@@ -2,6 +2,7 @@ import type { RuntimeRPC } from '../../types/rpc'
 import type { TestProject } from '../project'
 import type { ResolveSnapshotPathHandlerContext } from '../types/config'
 import { existsSync, mkdirSync } from 'node:fs'
+import { isBuiltin } from 'node:module'
 import { fileURLToPath } from 'node:url'
 import { cleanUrl } from '@vitest/utils/helpers'
 import { handleRollupError } from '../environments/fetchModule'
@@ -63,6 +64,17 @@ export function createMethodsRPC(project: TestProject, options: MethodsOptions =
       if (!resolved) {
         return null
       }
+      const file = cleanUrl(resolved.id)
+      if (resolved.external) {
+        return {
+          file,
+          // TODO: use isBuiltin defined in the environment
+          url: !resolved.id.startsWith('node:') && isBuiltin(resolved.id)
+            ? `node:${resolved.id}`
+            : resolved.id,
+          id: resolved.id,
+        }
+      }
       return {
         file: cleanUrl(resolved.id),
         url: normalizeResolvedIdToUrl(environment, resolved.id),

test/core/test/mocked-node-module.test.ts

@@ -0,0 +1,18 @@
+/* eslint-disable unicorn/prefer-node-protocol */
+
+import fs from 'fs/promises'
+import { expect, test, vi } from 'vitest'
+
+vi.mock(import('fs/promises'), async (importOriginal) => {
+  const { default: original } = await importOriginal()
+  return {
+    default: {
+      ...original,
+      readFile: vi.fn(),
+    },
+  }
+})
+
+test('fs is defined when node: prefix is not used', () => {
+  expect(vi.isMockFunction(fs.readFile)).toBe(true)
+})