From f535282c8d8792267e2e13763f614560bbb5ffe9 Mon Sep 17 00:00:00 2001
From: Manuel Schiller <manuel.schiller@caligano.de>
Date: Sat, 18 Oct 2025 00:02:51 +0200
Subject: [PATCH] fix: dev serverfn resolution on windows

---
 packages/server-functions-plugin/src/index.ts   | 17 ++++++++++++++++-
 .../src/fake-start-server-fn-manifest.ts        |  2 +-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/packages/server-functions-plugin/src/index.ts b/packages/server-functions-plugin/src/index.ts
index 97ba71a0bdd..e2d29b7822c 100644
--- a/packages/server-functions-plugin/src/index.ts
+++ b/packages/server-functions-plugin/src/index.ts
@@ -68,17 +68,32 @@ export function TanStackServerFnPlugin(
   const entryIdToFunctionId = new Map<string, string>()
   const functionIds = new Set<string>()
 
+  function withTrailingSlash(path: string): string {
+    if (path[path.length - 1] !== '/') {
+      return `${path}/`
+    }
+    return path
+  }
+
   const generateFunctionId: GenerateFunctionIdFn = ({
     extractedFilename,
     functionName,
     filename,
   }) => {
     if (serverDevEnv) {
+      const root = serverDevEnv.config.root
+
+      let file = extractedFilename
+      if (extractedFilename.startsWith(withTrailingSlash(root))) {
+        file = extractedFilename.slice(root.length)
+      }
+      file = `/@id${file[0] === '/' ? '' : '/'}${file}`
+
       const serverFn: {
         file: string
         export: string
       } = {
-        file: extractedFilename,
+        file,
         export: functionName,
       }
       const base64 = Buffer.from(JSON.stringify(serverFn), 'utf8').toString(
diff --git a/packages/start-server-core/src/fake-start-server-fn-manifest.ts b/packages/start-server-core/src/fake-start-server-fn-manifest.ts
index 9250d5dbf13..d1b5a0aeaf8 100644
--- a/packages/start-server-core/src/fake-start-server-fn-manifest.ts
+++ b/packages/start-server-core/src/fake-start-server-fn-manifest.ts
@@ -1 +1 @@
-export function getServerFnById() {}
+export async function getServerFnById(): Promise<any> {}