fix: handle case where path starts with root but isn't contained inside

Previously `getFsPath` would just replace the first occurrence of the
root path with the empty string (`path.replace(this.root, '')`). This
lead to incorrect behavior:

```js
const path = '/some/path/to/a/package-somewhere/index.js'
const root = '/some/path/to/a/package'
const result = path.replace(root, '')

// result _should_ be '/some/path/to/a/package-somewhere/index.js', but
// instead it's '-somewhere/index.js'
```

This fixes a bug I found while trying to write a test case for #1864.

packages/vite-node/src/utils.ts

@@ -14,6 +14,22 @@ export function mergeSlashes(str: string) {
   return str.replace(/\/\//g, '/')
 }
 
+export function snipBase(path: string, base: string) {
+  if (!base.endsWith('/'))
+    base += '/'
+
+  const isAtFS = path.startsWith('/@fs/')
+  if (isAtFS && !base.startsWith('/@fs/'))
+    base = base.startsWith('/') ? `/@fs${base}` : `/@fs/${base}`
+
+  if (path.startsWith(base)) {
+    // Subtract 1 to ensure the result has a leading slash
+    const snipped = path.slice(base.length - 1)
+    return isAtFS ? `/@fs${snipped}` : snipped
+  }
+  return path
+}
+
 export function normalizeRequestId(id: string, base?: string): string {
   if (base && id.startsWith(base))
     id = `/${id.slice(base.length)}`

packages/vitest/src/runtime/mocker.ts

@@ -1,7 +1,7 @@
 import { existsSync, readdirSync } from 'fs'
 import { isNodeBuiltin } from 'mlly'
 import { basename, dirname, join, resolve } from 'pathe'
-import { normalizeRequestId, toFilePath } from 'vite-node/utils'
+import { normalizeRequestId, snipBase, toFilePath } from 'vite-node/utils'
 import type { ModuleCacheMap } from 'vite-node/client'
 import { getAllMockableProperties, getType, getWorkerState, isWindows, mergeSlashes, slash } from '../utils'
 import { distDir } from '../constants'
@@ -142,14 +142,14 @@ export class VitestMocker {
   }
 
   public normalizePath(path: string) {
-    return normalizeRequestId(path.replace(this.root, ''), this.base).replace(/^\/@fs\//, isWindows ? '' : '/')
+    return normalizeRequestId(snipBase(path, this.root), this.base).replace(/^\/@fs\//, isWindows ? '' : '/')
   }
 
   public getFsPath(path: string, external: string | null) {
     if (external)
       return mergeSlashes(`/@fs/${path}`)
 
-    return normalizeRequestId(path.replace(this.root, ''))
+    return normalizeRequestId(snipBase(path, this.root))
   }
 
   public resolveMockPath(mockPath: string, external: string | null) {

test/path-resolution-target/.eslintignore

@@ -0,0 +1 @@
+!dist/

test/path-resolution-target/.gitignore

@@ -0,0 +1 @@
+!dist/

test/path-resolution-target/README.md

@@ -0,0 +1,2 @@
+This package is here just to be a sibling package to `path-resolution`. It
+contains no tests of its own.

test/path-resolution-target/dist/index.d.ts

@@ -0,0 +1 @@
+export function add(a: number, b: number): number

test/path-resolution-target/dist/index.js

@@ -0,0 +1,3 @@
+export function add(a, b) {
+  return a + b;
+}

test/path-resolution-target/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "@vitest/test-path-resolution-target",
+  "type": "module",
+  "private": true,
+  "main": "./dist/index.js"
+}

test/path-resolution/package.json

@@ -9,6 +9,7 @@
   "devDependencies": {
     "@edge-runtime/vm": "1.1.0-beta.26",
     "@vitest/test-path-res-target": "workspace:*",
+    "@vitest/test-path-resolution-target": "workspace:*",
     "@vitest/web-worker": "workspace:*",
     "vitest": "workspace:*"
   }

test/path-resolution/test/starts-with.test.ts

@@ -0,0 +1,17 @@
+import { expect, it, vitest } from 'vitest'
+
+import { add } from '@vitest/test-path-resolution-target'
+
+vitest.mock('@vitest/test-path-resolution-target')
+
+it('should be mocked', () => {
+  expect(add).toHaveProperty('mock')
+  expect(add(2, 3)).toBeUndefined()
+})
+
+it('should import actual', async () => {
+  const { add } = await vitest.importActual('@vitest/test-path-resolution-target')
+
+  expect(add).not.toHaveProperty('mock')
+  expect(add(2, 3)).toBe(5)
+})