fix(rsc): fix findSourceMapURL on Windows (#1025)

Author: hi-ogawa

packages/plugin-rsc/e2e/basic.test.ts

@@ -21,7 +21,7 @@ test.describe('dev-default', () => {
   const f = useFixture({ root: 'examples/basic', mode: 'dev' })
   defineTest(f)
 
-  test('validate findSourceMapURL', async () => {
+  test('validate findSourceMapURL - reject', async () => {
     const requestUrl = new URL(f.url('__vite_rsc_findSourceMapURL'))
     requestUrl.searchParams.set(
       'filename',
@@ -31,6 +31,20 @@ test.describe('dev-default', () => {
     const response = await fetch(requestUrl)
     expect(response.status).toBe(404)
   })
+
+  test('validate findSourceMapURL - pass', async () => {
+    const requestUrl = new URL(f.url('__vite_rsc_findSourceMapURL'))
+    requestUrl.searchParams.set(
+      'filename',
+      new URL('../examples/basic/package.json', import.meta.url).href,
+    )
+    requestUrl.searchParams.set('environmentName', 'Server')
+    const response = await fetch(requestUrl)
+    expect(response.status).toBe(200)
+    expect(await response.json()).toMatchObject({
+      version: 3,
+    })
+  })
 })
 
 test.describe('dev-initial', () => {

packages/plugin-rsc/src/plugins/find-source-map-url.ts

@@ -6,6 +6,7 @@ import {
   type ViteDevServer,
 } from 'vite'
 import fs from 'node:fs'
+import { slash } from './vite-utils'
 
 //
 // support findSourceMapURL
@@ -52,7 +53,7 @@ async function findSourceMapURL(
 ): Promise<object | undefined> {
   // this is likely server external (i.e. outside of Vite processing)
   if (filename.startsWith('file://')) {
-    filename = fileURLToPath(filename)
+    filename = slash(fileURLToPath(filename))
     if (
       isFileLoadingAllowed(server.config, filename) &&
       fs.existsSync(filename)