fix(v10/nitro): Use forward slashes for resolved plugin paths on Windows (#25692)

Backport of: #25023

Co-authored-by: Luís Silva <15066801+dasilvaluis@users.noreply.github.com>
Co-authored-by: GPT-6 <codex@openai.com>

Author: 3 people

packages/nitro/src/utils/resolver.ts

@@ -20,6 +20,9 @@ export function createResolver(base: string): Resolver {
   }
 
   return {
-    resolve: (...path) => resolve(resolvedBase, ...path),
+    // Nitro writes plugin paths verbatim into a generated `import "…"` statement, where the
+    // backslashes of a Windows path read as escape sequences (`C:\Users` becomes `C:Users`).
+    // Forward slashes resolve on every platform, so normalize to them.
+    resolve: (...path) => resolve(resolvedBase, ...path).replace(/\\/g, '/'),
   };
 }

packages/nitro/test/resolver.test.ts

@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest';
+import { createResolver } from '../src/utils/resolver';
+
+describe('createResolver', () => {
+  it('resolves relative to the directory of a file URL', () => {
+    const resolver = createResolver(import.meta.url);
+
+    expect(resolver.resolve('../src/utils/resolver.ts')).toMatch(/packages\/nitro\/src\/utils\/resolver\.ts$/);
+  });
+
+  it('never returns backslashes, so the path survives being written into an import string', () => {
+    const resolver = createResolver(import.meta.url);
+
+    expect(resolver.resolve('../runtime/plugins/server')).not.toContain('\\');
+  });
+});