fix(rsc): pass root importer explicitly instead of undefined for this.resolve in rsc:virtual-client-package

packages/plugin-rsc/examples/basic/vite.config.ts

@@ -32,6 +32,7 @@ export default defineConfig({
     react(),
     vitePluginUseCache(),
     vitePluginVirtualModuleTest(),
+    testRscVirtualClientPackagePlugin(),
     rsc({
       entries: {
         client: './src/framework/entry.browser.tsx',
@@ -271,6 +272,25 @@ export default { fetch: handler };
   },
 }) as any
 
+function testRscVirtualClientPackagePlugin(): Plugin {
+  return {
+    name: 'test-rsc-virtual-client-package',
+    enforce: 'pre',
+    resolveId(source, importer) {
+      // `rsc:virtual-client-package` should pass an explicit root importer.
+      if (
+        this.environment.name === 'rsc' &&
+        source === '@vitejs/test-dep-transitive-client/client' &&
+        importer == null
+      ) {
+        throw new Error(
+          '`rsc:virtual-client-package` root resolution requires an importer',
+        )
+      }
+    },
+  }
+}
+
 function testBuildPlugin(): Plugin[] {
   const moduleIds: { name: string; ids: string[] }[] = []
   return [

packages/plugin-rsc/src/plugin.ts

@@ -1720,9 +1720,15 @@ function vitePluginUseClient(
               // transitive dependency reachable from `importer` but not installed
               // at the root (see #1247). In that case, skip virtualization and
               // let it fall back to referencing the fully resolved module id.
+              // Vite's resolver already treats an undefined importer as the project
+              // root, but other plugins may not, so pass the root importer explicitly.
+              const rootImporter = path.join(
+                this.environment.config.root,
+                'index.html',
+              )
               const resolvedAtRoot = await this.resolve(
                 source,
-                undefined,
+                rootImporter,
                 options,
               )
               if (!resolvedAtRoot || resolvedAtRoot.id !== resolved.id) {