feat(dev): add moduleDirectories option to the vitest config

docs/api/vi.md

@@ -234,7 +234,7 @@ import { vi } from 'vitest'
   ```
   :::
 
-  If there is a `__mocks__` folder alongside a file that you are mocking, and the factory is not provided, Vitest will try to find a file with the same name in the `__mocks__` subfolder and use it as an actual module. If you are mocking a dependency, Vitest will try to find a `__mocks__` folder in the [root](/config/#root) of the project (default is `process.cwd()`).
+  If there is a `__mocks__` folder alongside a file that you are mocking, and the factory is not provided, Vitest will try to find a file with the same name in the `__mocks__` subfolder and use it as an actual module. If you are mocking a dependency, Vitest will try to find a `__mocks__` folder in the [root](/config/#root) of the project (default is `process.cwd()`). You can tell Vitest where the dependencies are located through the [deps.moduleDirectories](/config/#deps-moduledirectories) config option.
 
   For example, you have this file structure:
 

docs/config/index.md

@@ -190,6 +190,29 @@ TypeError: default is not a function
 
 By default, Vitest assumes you are using a bundler to bypass this and will not fail, but you can disable this behaviour manually, if you code is not processed.
 
+#### deps.moduleDirectories
+
+- **Type:** `string[]`
+- **Default**: `['node_modules']`
+
+A list of directories that should be treated as module directories. This config option affects the behavior of [`vi.mock`](/api/vi#vi-mock): when no factory is provided and the path of what you are mocking matches one of the `moduleDirectories` values, Vitest will try to resolve the mock by looking for a `__mocks__` folder in the [root](/config/#root) of the project.
+
+This option will also affect if a file should be treated as a module when externalizing dependencies. By default, Vitest imports external modules with native Node.js bypassing Vite transformation step.
+
+Setting this option will _override_ the default, if you wish to still search `node_modules` for packages include it along with any other options:
+
+```ts
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    deps: {
+      moduleDirectories: ['node_modules', path.resolve('../../packages')],
+    }
+  },
+})
+```
+
 ### runner
 
 - **Type**: `VitestRunnerConstructor`

examples/mocks/__mocks__/custom-lib.ts

@@ -0,0 +1,3 @@
+export default function () {
+  return 'mocked'
+}

examples/mocks/projects/custom-lib/index.js

@@ -0,0 +1,3 @@
+export default function () {
+  return 'original'
+}

examples/mocks/projects/custom-lib/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}

examples/mocks/test/custom-module-directory.spec.ts

@@ -0,0 +1,8 @@
+// @ts-expect-error not typed aliased import
+import getState from 'custom-lib'
+
+vi.mock('custom-lib')
+
+it('state is mocked', () => {
+  expect(getState()).toBe('mocked')
+})

examples/mocks/vite.config.ts

@@ -1,5 +1,6 @@
 /// <reference types="vitest" />
 
+import { resolve } from 'node:path'
 import { defineConfig } from 'vite'
 
 // https://vitejs.dev/config/
@@ -20,12 +21,18 @@ export default defineConfig({
       },
     },
   ],
+  resolve: {
+    alias: [
+      { find: /^custom-lib$/, replacement: resolve(__dirname, 'projects', 'custom-lib') },
+    ],
+  },
   test: {
     globals: true,
     environment: 'node',
     deps: {
       external: [/src\/external/],
       interopDefault: true,
+      moduleDirectories: ['node_modules', 'projects'],
     },
   },
 })

packages/vite-node/src/cli.ts

@@ -128,6 +128,9 @@ function parseServerOptions(serverOptions: ViteNodeServerOptionsCLI): ViteNodeSe
           ? new RegExp(dep)
           : dep
       }),
+      moduleDirectories: serverOptions.deps?.moduleDirectories
+        ? toArray(serverOptions.deps?.moduleDirectories)
+        : undefined,
     },
 
     transformMode: {

packages/vite-node/src/externalize.ts

@@ -1,5 +1,6 @@
 import { existsSync } from 'node:fs'
 import { isNodeBuiltin, isValidNodeImport } from 'mlly'
+import { join } from 'pathe'
 import type { DepsHandlingOptions } from './types'
 import { slash } from './utils'
 
@@ -109,35 +110,37 @@ async function _shouldExternalize(
   if (options?.cacheDir && id.includes(options.cacheDir))
     return id
 
-  if (matchExternalizePattern(id, options?.inline))
+  const moduleDirectories = options?.moduleDirectories || ['/node_modules/']
+
+  if (matchExternalizePattern(id, moduleDirectories, options?.inline))
     return false
-  if (matchExternalizePattern(id, options?.external))
+  if (matchExternalizePattern(id, moduleDirectories, options?.external))
     return id
 
-  const isNodeModule = id.includes('/node_modules/')
-  const guessCJS = isNodeModule && options?.fallbackCJS
+  const isLibraryModule = moduleDirectories.some(dir => id.includes(dir))
+  const guessCJS = isLibraryModule && options?.fallbackCJS
   id = guessCJS ? (guessCJSversion(id) || id) : id
 
-  if (matchExternalizePattern(id, defaultInline))
+  if (matchExternalizePattern(id, moduleDirectories, defaultInline))
     return false
-  if (matchExternalizePattern(id, depsExternal))
+  if (matchExternalizePattern(id, moduleDirectories, depsExternal))
     return id
 
   const isDist = id.includes('/dist/')
-  if ((isNodeModule || isDist) && await isValidNodeImport(id))
+  if ((isLibraryModule || isDist) && await isValidNodeImport(id))
     return id
 
   return false
 }
 
-function matchExternalizePattern(id: string, patterns?: (string | RegExp)[] | true) {
+function matchExternalizePattern(id: string, moduleDirectories: string[], patterns?: (string | RegExp)[] | true) {
   if (patterns == null)
     return false
   if (patterns === true)
     return true
   for (const ex of patterns) {
     if (typeof ex === 'string') {
-      if (id.includes(`/node_modules/${ex}/`))
+      if (moduleDirectories.some(dir => id.includes(join(dir, id))))
         return true
     }
     else {

packages/vite-node/src/types.ts

@@ -9,6 +9,7 @@ export type Awaitable<T> = T | PromiseLike<T>
 export interface DepsHandlingOptions {
   external?: (string | RegExp)[]
   inline?: (string | RegExp)[] | true
+  moduleDirectories?: string[]
   cacheDir?: string
   /**
    * Try to guess the CJS version of a package when it's invalid ESM

packages/vitest/src/node/config.ts

@@ -84,7 +84,7 @@ export function resolveConfig(
     ...options,
     root: viteConfig.root,
     mode,
-  } as ResolvedConfig
+  } as any as ResolvedConfig
 
   resolved.inspect = Boolean(resolved.inspect)
   resolved.inspectBrk = Boolean(resolved.inspectBrk)
@@ -136,6 +136,14 @@ export function resolveConfig(
       resolved.deps.inline.push(...extraInlineDeps)
     }
   }
+  resolved.deps.moduleDirectories ??= ['/node_modules/']
+  resolved.deps.moduleDirectories = resolved.deps.moduleDirectories.map((dir) => {
+    if (!dir.startsWith('/'))
+      dir = `/${dir}`
+    if (!dir.endsWith('/'))
+      dir += '/'
+    return normalize(dir)
+  })
 
   if (resolved.runner) {
     resolved.runner = resolveModule(resolved.runner, { paths: [resolved.root] })

packages/vitest/src/runtime/execute.ts

@@ -13,6 +13,7 @@ import { rpc } from './rpc'
 
 export interface ExecuteOptions extends ViteNodeRunnerOptions {
   mockMap: MockMap
+  moduleDirectories?: string[]
 }
 
 export async function createVitestExecutor(options: ExecuteOptions) {
@@ -70,6 +71,7 @@ export async function startViteNode(ctx: ContextRPC) {
     moduleCache,
     mockMap,
     interopDefault: config.deps.interopDefault,
+    moduleDirectories: config.deps.moduleDirectories,
     root: config.root,
     base: config.base,
   })

packages/vitest/src/runtime/mocker.ts

@@ -58,12 +58,20 @@ export class VitestMocker {
     return this.executor.moduleCache
   }
 
+  private get moduleDirectories() {
+    return this.executor.options.moduleDirectories || []
+  }
+
   private deleteCachedItem(id: string) {
     const mockId = this.getMockPath(id)
     if (this.moduleCache.has(mockId))
       this.moduleCache.delete(mockId)
   }
 
+  private isAModuleDirectory(path: string) {
+    return this.moduleDirectories.some(dir => path.includes(dir))
+  }
+
   public getSuiteFilepath(): string {
     return getWorkerState().filepath || 'global'
   }
@@ -83,7 +91,7 @@ export class VitestMocker {
     const [id, fsPath] = await this.executor.resolveUrl(rawId, importer)
     // external is node_module or unresolved module
     // for example, some people mock "vscode" and don't have it installed
-    const external = (!isAbsolute(fsPath) || fsPath.includes('/node_modules/')) ? rawId : null
+    const external = (!isAbsolute(fsPath) || this.isAModuleDirectory(fsPath)) ? rawId : null
 
     return {
       id,

packages/vitest/src/types/config.ts

@@ -116,6 +116,13 @@ interface DepsOptions {
    * @default false
    */
   registerNodeLoader?: boolean
+
+  /**
+   * A list of directories relative to the config file that should be treated as module directories.
+   *
+   * @default ['node_modules']
+   */
+  moduleDirectories?: string[]
 }
 
 export interface InlineConfig {
@@ -732,7 +739,7 @@ export type ProjectConfig = Omit<
   | 'coverage'
 > & {
   sequencer?: Omit<SequenceOptions, 'sequencer' | 'seed'>
-  deps?: Omit<DepsOptions, 'registerNodeLoader'>
+  deps?: Omit<DepsOptions, 'registerNodeLoader' | 'moduleDirectories'>
 }
 
 export type RuntimeConfig = Pick<

packages/web-worker/src/utils.ts

@@ -73,6 +73,7 @@ export function getRunnerOptions(): any {
     moduleCache,
     mockMap,
     interopDefault: config.deps.interopDefault ?? true,
+    moduleDirectories: config.deps.moduleDirectories,
     root: config.root,
     base: config.base,
   }

test/core/projects/custom-lib/index.js

@@ -0,0 +1,4 @@
+export default function () {
+  // module doesn't exist in Node.js ESM, but exists in vite-node
+  return typeof module
+}

test/core/projects/custom-lib/package.json

@@ -0,0 +1,3 @@
+{
+  "type": "module"
+}

test/core/test/external-module-directory.test.ts

@@ -0,0 +1,7 @@
+// @ts-expect-error not typed aliased import
+import getModuleType from 'custom-lib'
+import { expect, it } from 'vitest'
+
+it('custom-lib is externalized because it\'s a valid esm file in module directory', () => {
+  expect(getModuleType()).toBe('undefined')
+})

test/core/vitest.config.ts

@@ -35,6 +35,7 @@ export default defineConfig({
     alias: [
       { find: '#', replacement: resolve(__dirname, 'src') },
       { find: '$', replacement: 'src' },
+      { find: /^custom-lib$/, replacement: resolve(__dirname, 'projects', 'custom-lib') },
     ],
   },
   test: {
@@ -62,6 +63,7 @@ export default defineConfig({
     },
     deps: {
       external: ['tinyspy', /src\/external/],
+      moduleDirectories: ['node_modules', 'projects'],
     },
     alias: [
       {