feat: add server fn meta

e2e/react-start/server-functions/src/routeTree.gen.ts

@@ -38,6 +38,7 @@ import { Route as MiddlewareServerImportMiddlewareRouteImport } from './routes/m
 import { Route as MiddlewareSendServerFnRouteImport } from './routes/middleware/send-serverFn'
 import { Route as MiddlewareRequestMiddlewareRouteImport } from './routes/middleware/request-middleware'
 import { Route as MiddlewareMiddlewareFactoryRouteImport } from './routes/middleware/middleware-factory'
+import { Route as MiddlewareFunctionMetadataRouteImport } from './routes/middleware/function-metadata'
 import { Route as MiddlewareClientMiddlewareRouterRouteImport } from './routes/middleware/client-middleware-router'
 import { Route as CookiesSetRouteImport } from './routes/cookies/set'
 import { Route as AbortSignalMethodRouteImport } from './routes/abort-signal/$method'
@@ -191,6 +192,12 @@ const MiddlewareMiddlewareFactoryRoute =
     path: '/middleware/middleware-factory',
     getParentRoute: () => rootRouteImport,
   } as any)
+const MiddlewareFunctionMetadataRoute =
+  MiddlewareFunctionMetadataRouteImport.update({
+    id: '/middleware/function-metadata',
+    path: '/middleware/function-metadata',
+    getParentRoute: () => rootRouteImport,
+  } as any)
 const MiddlewareClientMiddlewareRouterRoute =
   MiddlewareClientMiddlewareRouterRouteImport.update({
     id: '/middleware/client-middleware-router',
@@ -233,6 +240,7 @@ export interface FileRoutesByFullPath {
   '/abort-signal/$method': typeof AbortSignalMethodRoute
   '/cookies/set': typeof CookiesSetRoute
   '/middleware/client-middleware-router': typeof MiddlewareClientMiddlewareRouterRoute
+  '/middleware/function-metadata': typeof MiddlewareFunctionMetadataRoute
   '/middleware/middleware-factory': typeof MiddlewareMiddlewareFactoryRoute
   '/middleware/request-middleware': typeof MiddlewareRequestMiddlewareRoute
   '/middleware/send-serverFn': typeof MiddlewareSendServerFnRoute
@@ -268,6 +276,7 @@ export interface FileRoutesByTo {
   '/abort-signal/$method': typeof AbortSignalMethodRoute
   '/cookies/set': typeof CookiesSetRoute
   '/middleware/client-middleware-router': typeof MiddlewareClientMiddlewareRouterRoute
+  '/middleware/function-metadata': typeof MiddlewareFunctionMetadataRoute
   '/middleware/middleware-factory': typeof MiddlewareMiddlewareFactoryRoute
   '/middleware/request-middleware': typeof MiddlewareRequestMiddlewareRoute
   '/middleware/send-serverFn': typeof MiddlewareSendServerFnRoute
@@ -304,6 +313,7 @@ export interface FileRoutesById {
   '/abort-signal/$method': typeof AbortSignalMethodRoute
   '/cookies/set': typeof CookiesSetRoute
   '/middleware/client-middleware-router': typeof MiddlewareClientMiddlewareRouterRoute
+  '/middleware/function-metadata': typeof MiddlewareFunctionMetadataRoute
   '/middleware/middleware-factory': typeof MiddlewareMiddlewareFactoryRoute
   '/middleware/request-middleware': typeof MiddlewareRequestMiddlewareRoute
   '/middleware/send-serverFn': typeof MiddlewareSendServerFnRoute
@@ -341,6 +351,7 @@ export interface FileRouteTypes {
     | '/abort-signal/$method'
     | '/cookies/set'
     | '/middleware/client-middleware-router'
+    | '/middleware/function-metadata'
     | '/middleware/middleware-factory'
     | '/middleware/request-middleware'
     | '/middleware/send-serverFn'
@@ -376,6 +387,7 @@ export interface FileRouteTypes {
     | '/abort-signal/$method'
     | '/cookies/set'
     | '/middleware/client-middleware-router'
+    | '/middleware/function-metadata'
     | '/middleware/middleware-factory'
     | '/middleware/request-middleware'
     | '/middleware/send-serverFn'
@@ -411,6 +423,7 @@ export interface FileRouteTypes {
     | '/abort-signal/$method'
     | '/cookies/set'
     | '/middleware/client-middleware-router'
+    | '/middleware/function-metadata'
     | '/middleware/middleware-factory'
     | '/middleware/request-middleware'
     | '/middleware/send-serverFn'
@@ -447,6 +460,7 @@ export interface RootRouteChildren {
   AbortSignalMethodRoute: typeof AbortSignalMethodRoute
   CookiesSetRoute: typeof CookiesSetRoute
   MiddlewareClientMiddlewareRouterRoute: typeof MiddlewareClientMiddlewareRouterRoute
+  MiddlewareFunctionMetadataRoute: typeof MiddlewareFunctionMetadataRoute
   MiddlewareMiddlewareFactoryRoute: typeof MiddlewareMiddlewareFactoryRoute
   MiddlewareRequestMiddlewareRoute: typeof MiddlewareRequestMiddlewareRoute
   MiddlewareSendServerFnRoute: typeof MiddlewareSendServerFnRoute
@@ -669,6 +683,13 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof MiddlewareMiddlewareFactoryRouteImport
       parentRoute: typeof rootRouteImport
     }
+    '/middleware/function-metadata': {
+      id: '/middleware/function-metadata'
+      path: '/middleware/function-metadata'
+      fullPath: '/middleware/function-metadata'
+      preLoaderRoute: typeof MiddlewareFunctionMetadataRouteImport
+      parentRoute: typeof rootRouteImport
+    }
     '/middleware/client-middleware-router': {
       id: '/middleware/client-middleware-router'
       path: '/middleware/client-middleware-router'
@@ -719,6 +740,7 @@ const rootRouteChildren: RootRouteChildren = {
   AbortSignalMethodRoute: AbortSignalMethodRoute,
   CookiesSetRoute: CookiesSetRoute,
   MiddlewareClientMiddlewareRouterRoute: MiddlewareClientMiddlewareRouterRoute,
+  MiddlewareFunctionMetadataRoute: MiddlewareFunctionMetadataRoute,
   MiddlewareMiddlewareFactoryRoute: MiddlewareMiddlewareFactoryRoute,
   MiddlewareRequestMiddlewareRoute: MiddlewareRequestMiddlewareRoute,
   MiddlewareSendServerFnRoute: MiddlewareSendServerFnRoute,

e2e/react-start/server-functions/src/routes/middleware/function-metadata.tsx

@@ -0,0 +1,164 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { createMiddleware, createServerFn } from '@tanstack/react-start'
+import React from 'react'
+
+const metadataMiddleware = createMiddleware({ type: 'function' })
+  .client(async ({ next, serverFnMeta }) => {
+    return next({
+      sendContext: {
+        clientCapturedMeta: serverFnMeta,
+      },
+    })
+  })
+  .server(async ({ next, serverFnMeta, context }) => {
+    return next({
+      context: {
+        serverCapturedMeta: serverFnMeta,
+        clientCapturedMeta: context.clientCapturedMeta,
+      },
+    })
+  })
+
+// Server function that returns both client and server captured metadata
+const getMetadataFn = createServerFn()
+  .middleware([metadataMiddleware])
+  .handler(async ({ context }) => {
+    return {
+      // Full metadata captured by server middleware
+      serverMeta: context.serverCapturedMeta,
+      // Metadata captured by client middleware and sent via sendContext
+      // Client middleware only has { id }, not { name, filename }
+      clientCapturedMeta: context.clientCapturedMeta,
+    }
+  })
+
+export const Route = createFileRoute('/middleware/function-metadata')({
+  loader: () => getMetadataFn(),
+  component: RouteComponent,
+})
+
+function RouteComponent() {
+  const loaderData = Route.useLoaderData()
+
+  const [clientData, setClientData] = React.useState<typeof loaderData | null>(
+    null,
+  )
+
+  return (
+    <div>
+      <h2>Function Metadata in Middleware</h2>
+      <p>
+        This test verifies that both client and server middleware receive
+        serverFnMeta in their options. Client middleware gets only the id, while
+        server middleware gets the full metadata (id, name, filename).
+      </p>
+      <br />
+      <div>
+        <div data-testid="loader-data">
+          <h3>Loader Data (SSR)</h3>
+          <h4>Server Captured Metadata:</h4>
+          <div>
+            Function ID:{' '}
+            <span data-testid="loader-function-id">
+              {loaderData.serverMeta?.id}
+            </span>
+          </div>
+          <div>
+            Function Name:{' '}
+            <span data-testid="loader-function-name">
+              {loaderData.serverMeta?.name}
+            </span>
+          </div>
+          <div>
+            Filename:{' '}
+            <span data-testid="loader-filename">
+              {loaderData.serverMeta?.filename}
+            </span>
+          </div>
+          <h4>Client Captured Metadata (via sendContext):</h4>
+          <p>Client middleware only receives id, not name or filename:</p>
+          <div>
+            Client Captured ID:{' '}
+            <span data-testid="loader-client-captured-id">
+              {loaderData.clientCapturedMeta?.id}
+            </span>
+          </div>
+          <div>
+            Client Captured Name:{' '}
+            <span data-testid="loader-client-captured-name">
+              {/* Cast to any to test that name is not present at runtime */}
+              {(loaderData.clientCapturedMeta as any)?.name ?? 'undefined'}
+            </span>
+          </div>
+          <div>
+            Client Captured Filename:{' '}
+            <span data-testid="loader-client-captured-filename">
+              {/* Cast to any to test that filename is not present at runtime */}
+              {(loaderData.clientCapturedMeta as any)?.filename ?? 'undefined'}
+            </span>
+          </div>
+        </div>
+        <br />
+        <div>
+          <button
+            data-testid="call-server-fn-btn"
+            onClick={async () => {
+              const data = await getMetadataFn()
+              setClientData(data)
+            }}
+          >
+            Call server function from client
+          </button>
+        </div>
+        <br />
+        {clientData && (
+          <div data-testid="client-data">
+            <h3>Client Data</h3>
+            <h4>Server Captured Metadata:</h4>
+            <div>
+              Function ID:{' '}
+              <span data-testid="client-function-id">
+                {clientData.serverMeta?.id}
+              </span>
+            </div>
+            <div>
+              Function Name:{' '}
+              <span data-testid="client-function-name">
+                {clientData.serverMeta?.name}
+              </span>
+            </div>
+            <div>
+              Filename:{' '}
+              <span data-testid="client-filename">
+                {clientData.serverMeta?.filename}
+              </span>
+            </div>
+            <h4>Client Captured Metadata (via sendContext):</h4>
+            <p>Client middleware only receives id, not name or filename:</p>
+            <div>
+              Client Captured ID:{' '}
+              <span data-testid="client-client-captured-id">
+                {clientData.clientCapturedMeta?.id}
+              </span>
+            </div>
+            <div>
+              Client Captured Name:{' '}
+              <span data-testid="client-client-captured-name">
+                {/* Cast to any to test that name is not present at runtime */}
+                {(clientData.clientCapturedMeta as any)?.name ?? 'undefined'}
+              </span>
+            </div>
+            <div>
+              Client Captured Filename:{' '}
+              <span data-testid="client-client-captured-filename">
+                {/* Cast to any to test that filename is not present at runtime */}
+                {(clientData.clientCapturedMeta as any)?.filename ??
+                  'undefined'}
+              </span>
+            </div>
+          </div>
+        )}
+      </div>
+    </div>
+  )
+}

e2e/react-start/server-functions/src/routes/middleware/index.tsx

@@ -50,6 +50,14 @@ function RouteComponent() {
             build
           </Route.Link>
         </li>
+        <li>
+          <Route.Link
+            to="./function-metadata"
+            data-testid="function-metadata-link"
+          >
+            Function middleware receives functionId and filename
+          </Route.Link>
+        </li>
       </ul>
     </div>
   )

e2e/react-start/server-functions/tests/server-functions.spec.ts

@@ -664,3 +664,86 @@ test('middleware factories with server-only imports are stripped from client bui
     'x-factory-two',
   )
 })
+
+test('function middleware receives serverFnMeta in options', async ({
+  page,
+}) => {
+  // This test verifies that:
+  // 1. Client middleware receives serverFnMeta with just { id } - NOT name or filename
+  // 2. Server middleware receives serverFnMeta with full { id, name, filename }
+  // 3. Client middleware can send the function metadata to the server via sendContext
+  await page.goto('/middleware/function-metadata')
+
+  await page.waitForLoadState('networkidle')
+
+  // Verify SSR data - server captured metadata should have full properties
+  const loaderFunctionId = await page
+    .getByTestId('loader-function-id')
+    .textContent()
+  const loaderFunctionName = await page
+    .getByTestId('loader-function-name')
+    .textContent()
+  const loaderFilename = await page.getByTestId('loader-filename').textContent()
+  const loaderClientCapturedId = await page
+    .getByTestId('loader-client-captured-id')
+    .textContent()
+  const loaderClientCapturedName = await page
+    .getByTestId('loader-client-captured-name')
+    .textContent()
+  const loaderClientCapturedFilename = await page
+    .getByTestId('loader-client-captured-filename')
+    .textContent()
+
+  // id should be a non-empty string
+  expect(loaderFunctionId).toBeTruthy()
+  expect(loaderFunctionId!.length).toBeGreaterThan(0)
+
+  // name should be the variable name of the server function
+  expect(loaderFunctionName).toBeTruthy()
+  expect(loaderFunctionName).toBe('getMetadataFn')
+
+  // filename should be the exact route file path
+  expect(loaderFilename).toBe('src/routes/middleware/function-metadata.tsx')
+
+  // Client captured ID should match the server function id
+  // (sent via client middleware's sendContext)
+  expect(loaderClientCapturedId).toBe(loaderFunctionId)
+
+  // Client middleware should NOT have access to name or filename
+  // These should be "undefined" (the fallback value we display in the UI)
+  expect(loaderClientCapturedName).toBe('undefined')
+  expect(loaderClientCapturedFilename).toBe('undefined')
+
+  // Now test client-side call
+  await page.getByTestId('call-server-fn-btn').click()
+  await page.waitForSelector('[data-testid="client-data"]')
+
+  const clientFunctionId = await page
+    .getByTestId('client-function-id')
+    .textContent()
+  const clientFunctionName = await page
+    .getByTestId('client-function-name')
+    .textContent()
+  const clientFilename = await page.getByTestId('client-filename').textContent()
+  const clientClientCapturedId = await page
+    .getByTestId('client-client-captured-id')
+    .textContent()
+  const clientClientCapturedName = await page
+    .getByTestId('client-client-captured-name')
+    .textContent()
+  const clientClientCapturedFilename = await page
+    .getByTestId('client-client-captured-filename')
+    .textContent()
+
+  // Client call should get the same server metadata
+  expect(clientFunctionId).toBe(loaderFunctionId)
+  expect(clientFunctionName).toBe(loaderFunctionName)
+  expect(clientFilename).toBe(loaderFilename)
+
+  // Client captured ID from client middleware should also match
+  expect(clientClientCapturedId).toBe(loaderFunctionId)
+
+  // Client middleware should NOT have access to name or filename
+  expect(clientClientCapturedName).toBe('undefined')
+  expect(clientClientCapturedFilename).toBe('undefined')
+})

packages/start-client-core/src/client-rpc/createClientRpc.ts

@@ -1,16 +1,18 @@
 import { TSS_SERVER_FUNCTION } from '../constants'
+import type { ClientFnMeta } from '../constants'
 import { serverFnFetcher } from './serverFnFetcher'
 
 export function createClientRpc(functionId: string) {
   const url = process.env.TSS_SERVER_FN_BASE + functionId
+  const serverFnMeta: ClientFnMeta = { id: functionId }
 
   const clientFn = (...args: Array<any>) => {
     return serverFnFetcher(url, args, fetch)
   }
 
   return Object.assign(clientFn, {
     url,
-    functionId,
+    serverFnMeta,
     [TSS_SERVER_FUNCTION]: true,
   })
 }