feat!: throw an error, if module cannot be resolved

docs/.vitepress/config.ts

@@ -215,6 +215,10 @@ export default withPwa(defineConfig({
               text: 'Migration Guide',
               link: '/guide/migration',
             },
+            {
+              text: 'Common Errors',
+              link: '/guide/common-errors',
+            },
           ],
         },
         {

docs/guide/common-errors.md

@@ -0,0 +1,40 @@
+# Common Errors
+
+## Cannot find module './relative-path'
+
+If you receive an error that module cannot be found, it might mean several different things:
+
+- 1. You misspelled the path. Make sure the path is correct.
+
+- 2. It's possible that your rely on `baseUrl` in your `tsconfig.json`. Vite doesn't take into account `tsconfig.json` by default, so you might need to install [`vite-tsconfig-paths`](https://www.npmjs.com/package/vite-tsconfig-paths) yourself, if you rely on this behaviour.
+
+```ts
+import { defineConfig } from 'vitest/config'
+import tsconfigPaths from 'vite-tsconfig-paths'
+
+export default defineConfig({
+  plugins: [tsconfigPaths()]
+})
+```
+
+Or rewrite your path to not be relative to root:
+
+```diff
+- import helpers from 'src/helpers'
++ import helpers from '../src/helpers'
+```
+
+- 3. Make sure you don't have relative [aliases](/config/#alias). Vite treats them as relative to the file where the import is instead of the root.
+
+```diff
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    alias: {
+-     '@/': './src/',
++     '@/': new URL('./src/', import.meta.url).pathname,
+    }
+  }
+})
+```

packages/vite-node/src/client.ts

@@ -219,7 +219,7 @@ export class ViteNodeRunner {
   }
 
   shouldResolveId(id: string, _importee?: string) {
-    return !isInternalRequest(id) && !isNodeBuiltin(id)
+    return !isInternalRequest(id) && !isNodeBuiltin(id) && !id.startsWith('data:')
   }
 
   private async _resolveUrl(id: string, importer?: string): Promise<[url: string, fsPath: string]> {
@@ -234,12 +234,18 @@ export class ViteNodeRunner {
     if (!this.options.resolveId || exists)
       return [id, path]
     const resolved = await this.options.resolveId(id, importer)
-    const resolvedId = resolved
-      ? normalizeRequestId(resolved.id, this.options.base)
-      : id
-    // to be compatible with dependencies that do not resolve id
-    const fsPath = resolved ? resolvedId : path
-    return [resolvedId, fsPath]
+    if (!resolved) {
+      const error = new Error(
+        `Cannot find module '${id}'${importer ? ` imported from '${importer}'` : ''}.`
+        + '\n\n- If you rely on tsconfig.json to resolve modules, please install "vite-tsconfig-paths" plugin to handle module resolution.'
+        + '\n - Make sure you don\'t have relative aliases in your Vitest config. Use absolute paths instead. Read more: https://vitest.dev/guide/common-errors',
+      )
+      Object.defineProperty(error, 'code', { value: 'ERR_MODULE_NOT_FOUND', enumerable: true })
+      Object.defineProperty(error, Symbol.for('vitest.error.not_found.data'), { value: { id, importer }, enumerable: false })
+      throw error
+    }
+    const resolvedId = normalizeRequestId(resolved.id, this.options.base)
+    return [resolvedId, resolvedId]
   }
 
   async resolveUrl(id: string, importee?: string) {

packages/vitest/src/runtime/execute.ts

@@ -97,18 +97,37 @@ export class VitestExecutor extends ViteNodeRunner {
   }
 
   shouldResolveId(id: string, _importee?: string | undefined): boolean {
-    if (isInternalRequest(id))
+    if (isInternalRequest(id) || id.startsWith('data:'))
       return false
     const environment = getCurrentEnvironment()
     // do not try and resolve node builtins in Node
     // import('url') returns Node internal even if 'url' package is installed
     return environment === 'node' ? !isNodeBuiltin(id) : !id.startsWith('node:')
   }
 
+  async originalResolveUrl(id: string, importer?: string) {
+    return super.resolveUrl(id, importer)
+  }
+
   async resolveUrl(id: string, importer?: string) {
+    if (VitestMocker.pendingIds.length)
+      await this.mocker.resolveMocks()
+
     if (importer && importer.startsWith('mock:'))
       importer = importer.slice(5)
-    return super.resolveUrl(id, importer)
+    try {
+      return await super.resolveUrl(id, importer)
+    }
+    catch (error: any) {
+      if (error.code === 'ERR_MODULE_NOT_FOUND') {
+        const { id } = error[Symbol.for('vitest.error.not_found.data')]
+        const path = this.mocker.normalizePath(id)
+        const mock = this.mocker.getDependencyMock(path)
+        if (mock !== undefined)
+          return [id, id] as [string, string]
+      }
+      throw error
+    }
   }
 
   async dependencyRequest(id: string, fsPath: string, callstack: string[]): Promise<any> {

packages/vitest/src/runtime/mocker.ts

@@ -39,7 +39,7 @@ function isSpecialProp(prop: Key, parentType: string) {
 }
 
 export class VitestMocker {
-  private static pendingIds: PendingSuiteMock[] = []
+  public static pendingIds: PendingSuiteMock[] = []
   private resolveCache = new Map<string, Record<string, string>>()
 
   constructor(
@@ -80,7 +80,22 @@ export class VitestMocker {
   }
 
   private async resolvePath(rawId: string, importer: string) {
-    const [id, fsPath] = await this.executor.resolveUrl(rawId, importer)
+    let id: string
+    let fsPath: string
+    try {
+      [id, fsPath] = await this.executor.originalResolveUrl(rawId, importer)
+    }
+    catch (error: any) {
+      // it's allowed to mock unresolved modules
+      if (error.code === 'ERR_MODULE_NOT_FOUND') {
+        const { id: unresolvedId } = error[Symbol.for('vitest.error.not_found.data')]
+        id = unresolvedId
+        fsPath = unresolvedId
+      }
+      else {
+        throw error
+      }
+    }
     // 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
@@ -92,7 +107,10 @@ export class VitestMocker {
     }
   }
 
-  private async resolveMocks() {
+  public async resolveMocks() {
+    if (!VitestMocker.pendingIds.length)
+      return
+
     await Promise.all(VitestMocker.pendingIds.map(async (mock) => {
       const { fsPath, external } = await this.resolvePath(mock.id, mock.importer)
       if (mock.type === 'unmock')
@@ -340,9 +358,6 @@ export class VitestMocker {
   }
 
   public async requestWithMock(url: string, callstack: string[]) {
-    if (VitestMocker.pendingIds.length)
-      await this.resolveMocks()
-
     const id = this.normalizePath(url)
     const mock = this.getDependencyMock(id)
 

packages/web-worker/src/shared-worker.ts

@@ -110,7 +110,7 @@ export function createSharedWorkerConstructor(): typeof SharedWorker {
 
         debug('initialize shared worker %s', this._vw_name)
 
-        runner.executeFile(fsPath).then(() => {
+        return runner.executeFile(fsPath).then(() => {
           // worker should be new every time, invalidate its sub dependency
           runnerOptions.moduleCache.invalidateSubDepTree([fsPath, runner.mocker.getMockPath(fsPath)])
           this._vw_workerTarget.dispatchEvent(
@@ -119,17 +119,17 @@ export function createSharedWorkerConstructor(): typeof SharedWorker {
             }),
           )
           debug('shared worker %s successfully initialized', this._vw_name)
-        }).catch((e) => {
-          debug('shared worker %s failed to initialize: %o', this._vw_name, e)
-          const EventConstructor = globalThis.ErrorEvent || globalThis.Event
-          const error = new EventConstructor('error', {
-            error: e,
-            message: e.message,
-          })
-          this.dispatchEvent(error)
-          this.onerror?.(error)
-          console.error(e)
         })
+      }).catch((e) => {
+        debug('shared worker %s failed to initialize: %o', this._vw_name, e)
+        const EventConstructor = globalThis.ErrorEvent || globalThis.Event
+        const error = new EventConstructor('error', {
+          error: e,
+          message: e.message,
+        })
+        this.dispatchEvent(error)
+        this.onerror?.(error)
+        console.error(e)
       })
     }
   }

packages/web-worker/src/worker.ts

@@ -75,25 +75,25 @@ export function createWorkerConstructor(options?: DefineWorkerOptions): typeof W
 
         debug('initialize worker %s', this._vw_name)
 
-        runner.executeFile(fsPath).then(() => {
+        return runner.executeFile(fsPath).then(() => {
           // worker should be new every time, invalidate its sub dependency
           runnerOptions.moduleCache.invalidateSubDepTree([fsPath, runner.mocker.getMockPath(fsPath)])
           const q = this._vw_messageQueue
           this._vw_messageQueue = null
           if (q)
             q.forEach(([data, transfer]) => this.postMessage(data, transfer), this)
           debug('worker %s successfully initialized', this._vw_name)
-        }).catch((e) => {
-          debug('worker %s failed to initialize: %o', this._vw_name, e)
-          const EventConstructor = globalThis.ErrorEvent || globalThis.Event
-          const error = new EventConstructor('error', {
-            error: e,
-            message: e.message,
-          })
-          this.dispatchEvent(error)
-          this.onerror?.(error)
-          console.error(e)
         })
+      }).catch((e) => {
+        debug('worker %s failed to initialize: %o', this._vw_name, e)
+        const EventConstructor = globalThis.ErrorEvent || globalThis.Event
+        const error = new EventConstructor('error', {
+          error: e,
+          message: e.message,
+        })
+        this.dispatchEvent(error)
+        this.onerror?.(error)
+        console.error(e)
       })
     }
 

test/core/test/imports.test.ts

@@ -68,9 +68,9 @@ test('dynamic import has null prototype', async () => {
 test('dynamic import throws an error', async () => {
   const path = './some-unknown-path'
   const imported = import(path)
-  await expect(imported).rejects.toThrowError(/Failed to load/)
+  await expect(imported).rejects.toThrowError(/Cannot find module '\.\/some-unknown-path'/)
   // @ts-expect-error path does not exist
-  await expect(() => import('./some-unknown-path')).rejects.toThrowError(/Failed to load/)
+  await expect(() => import('./some-unknown-path')).rejects.toThrowError(/Cannot find module/)
 })
 
 test('can import @vite/client', async () => {

test/core/test/unmock-import.test.ts

@@ -20,7 +20,7 @@ test('first import', async () => {
   expect(data.state).toBe('STOPPED')
 })
 
-test('second import should had been re-mock', async () => {
+test('second import should have been re-mocked', async () => {
   // @ts-expect-error I know this
   const { data } = await import('/data')
   expect(data.state).toBe('STARTED')

test/web-worker/test/init.test.ts

@@ -66,7 +66,7 @@ it('worker with invalid url throws an error', async () => {
   })
   expect(event).toBeInstanceOf(ErrorEvent)
   expect(event.error).toBeInstanceOf(Error)
-  expect(event.error.message).toContain('Failed to load')
+  expect(event.error.message).toContain('Cannot find module')
 })
 
 it('self injected into worker and its deps should be equal', async () => {

test/web-worker/test/sharedWorker.spec.ts

@@ -1,5 +1,5 @@
 import { expect, it } from 'vitest'
-import MySharedWorker from './src/sharedWorker?sharedworker'
+import MySharedWorker from '../src/sharedWorker?sharedworker'
 
 function sendEventMessage(worker: SharedWorker, msg: any) {
   worker.port.postMessage(msg)
@@ -50,7 +50,7 @@ it('throws an error on invalid path', async () => {
   })
   expect(event).toBeInstanceOf(ErrorEvent)
   expect(event.error).toBeInstanceOf(Error)
-  expect(event.error.message).toContain('Failed to load')
+  expect(event.error.message).toContain('Cannot find module')
 })
 
 it('doesn\'t trigger events, if closed', async () => {

test/web-worker/vitest.config.ts

@@ -12,7 +12,7 @@ export default defineConfig({
       ],
     },
     onConsoleLog(log) {
-      if (log.includes('Failed to load'))
+      if (log.includes('Cannot find module'))
         return false
     },
   },