fix(vitest): correctly resolve mocked node:* imports in __mocks__ folder (#6204)

Author: sheremet-va

Diff for: docs/guide/mocking.md

@@ -383,19 +383,19 @@ module.exports = fs.promises
 :::
 
 ```ts
-// hello-world.js
+// read-hello-world.js
 import { readFileSync } from 'node:fs'
 
 export function readHelloWorld(path) {
-  return readFileSync('./hello-world.txt')
+  return readFileSync(path)
 }
 ```
 
 ```ts
 // hello-world.test.js
 import { beforeEach, expect, it, vi } from 'vitest'
 import { fs, vol } from 'memfs'
-import { readHelloWorld } from './hello-world.js'
+import { readHelloWorld } from './read-hello-world.js'
 
 // tell vitest to use fs mock from __mocks__ folder
 // this can be done in a setup file if fs should always be mocked
@@ -408,7 +408,7 @@ beforeEach(() => {
 })
 
 it('should return correct text', () => {
-  const path = './hello-world.txt'
+  const path = '/hello-world.txt'
   fs.writeFileSync(path, 'hello world')
 
   const text = readHelloWorld(path)
@@ -423,7 +423,7 @@ it('can return a value multiple times', () => {
       './dir2/hw.txt': 'hello dir2',
     },
     // default cwd
-    '/tmp'
+    '/tmp',
   )
 
   expect(readHelloWorld('/tmp/dir1/hw.txt')).toBe('hello dir1')

Diff for: packages/vitest/src/runtime/mocker.ts

@@ -188,7 +188,7 @@ export class VitestMocker {
     return {
       id,
       fsPath,
-      external,
+      external: external ? this.normalizePath(external) : external,
     }
   }
 
@@ -315,14 +315,28 @@ export class VitestMocker {
       const files = readdirSync(mockFolder)
       const baseOriginal = basename(path)
 
-      for (const file of files) {
-        const baseFile = basename(file, extname(file))
-        if (baseFile === baseOriginal) {
-          return resolve(mockFolder, file)
+      function findFile(files: string[], baseOriginal: string): string | null {
+        for (const file of files) {
+          const baseFile = basename(file, extname(file))
+          if (baseFile === baseOriginal) {
+            const path = resolve(mockFolder, file)
+            // if the same name, return the file
+            if (fs.statSync(path).isFile()) {
+              return path
+            }
+            else {
+              // find folder/index.{js,ts}
+              const indexFile = findFile(readdirSync(path), 'index')
+              if (indexFile) {
+                return indexFile
+              }
+            }
+          }
         }
+        return null
       }
 
-      return null
+      return findFile(files, baseOriginal)
     }
 
     const dir = dirname(path)
@@ -517,7 +531,7 @@ export class VitestMocker {
     const mocks = this.mockMap.get(suitefile) || {}
     const resolves = this.resolveCache.get(suitefile) || {}
 
-    mocks[id] = factory || this.resolveMockPath(path, external)
+    mocks[id] = factory || this.resolveMockPath(id, external)
     resolves[id] = originalId
 
     this.mockMap.set(suitefile, mocks)
@@ -546,7 +560,7 @@ export class VitestMocker {
     let mock = this.getDependencyMock(normalizedId)
 
     if (mock === undefined) {
-      mock = this.resolveMockPath(fsPath, external)
+      mock = this.resolveMockPath(normalizedId, external)
     }
 
     if (mock === null) {

Diff for: pnpm-lock.yaml

@@ -0,0 +1,6 @@
+// we can also use `import`, but then
+// every export should be explicitly defined
+
+const { fs } = require('memfs')
+
+module.exports = fs

Diff for: test/core/__mocks__/fs.cjs

@@ -0,0 +1,6 @@
+// we can also use `import`, but then
+// every export should be explicitly defined
+
+const { fs } = require('memfs')
+
+module.exports = fs.promises

Diff for: test/core/__mocks__/fs/promises.cjs

@@ -23,6 +23,7 @@
     "axios": "^0.26.1",
     "debug": "^4.3.4",
     "immutable": "5.0.0-beta.5",
+    "memfs": "^4.8.2",
     "strip-ansi": "^7.1.0",
     "sweetalert2": "^11.6.16",
     "tinyrainbow": "^1.2.0",

Diff for: test/core/package.json

@@ -0,0 +1,6 @@
+// hello-world.js
+import { readFileSync } from 'node:fs'
+
+export function readHelloWorld(path: string) {
+  return readFileSync(path, 'utf-8')
+}

Diff for: test/core/src/read-hello-world.ts

@@ -2,7 +2,11 @@ import { existsSync } from 'node:fs'
 import { describe, expect, it, vi } from 'vitest'
 import { isWindows, slash, toFilePath } from '../../../packages/vite-node/src/utils'
 
-vi.mock('fs')
+vi.mock('fs', () => {
+  return {
+    existsSync: vi.fn(),
+  }
+})
 
 describe('current url', () => {
   it('__filename is equal to import.meta.url', () => {

Diff for: test/core/test/file-path.test.ts

@@ -0,0 +1,37 @@
+// hello-world.test.js
+import { beforeEach, expect, it, vi } from 'vitest'
+import { fs, vol } from 'memfs'
+import { readHelloWorld } from '../src/read-hello-world'
+
+// tell vitest to use fs mock from __mocks__ folder
+// this can be done in a setup file if fs should always be mocked
+vi.mock('node:fs')
+vi.mock('node:fs/promises')
+
+beforeEach(() => {
+  // reset the state of in-memory fs
+  vol.reset()
+})
+
+it('should return correct text', () => {
+  const path = '/hello-world.txt'
+  fs.writeFileSync(path, 'hello world')
+
+  const text = readHelloWorld(path)
+  expect(text).toBe('hello world')
+})
+
+it('can return a value multiple times', () => {
+  // you can use vol.fromJSON to define several files
+  vol.fromJSON(
+    {
+      './dir1/hw.txt': 'hello dir1',
+      './dir2/hw.txt': 'hello dir2',
+    },
+    // default cwd
+    '/tmp',
+  )
+
+  expect(readHelloWorld('/tmp/dir1/hw.txt')).toBe('hello dir1')
+  expect(readHelloWorld('/tmp/dir2/hw.txt')).toBe('hello dir2')
+})