TanStack Server Functions Plugin

Configuration

Create a new instance of the plugin with the following options:

const TanStackServerFnsPlugin = createTanStackServerFnPlugin({
  // This is the ID that will be available to look up and import
  // our server function manifest and resolve its module
  manifestVirtualImportId: 'tsr:server-fn-manifest',
  client: {
    getRuntimeCode: () =>
      `import { createClientRpc } from '@tanstack/react-start/client-runtime'`,
    replacer: (opts) => `createClientRpc(${JSON.stringify(opts.functionId)})`,
  },
  ssr: {
    getRuntimeCode: () =>
      `import { createSsrRpc } from '@tanstack/react-start/ssr-runtime'`,
    replacer: (opts) => `createSsrRpc(${JSON.stringify(opts.functionId)})`,
  },
  server: {
    getRuntimeCode: () =>
      `import { createServerRpc } from '@tanstack/react-start/server-runtime'`,
    replacer: (opts) =>
      `createServerRpc(${JSON.stringify(opts.functionId)}, ${opts.fn})`,
  },
})

Then you can inject the plugin into the appropriate vite config plugin arrays:

clientVitePlugins: [TanStackServerFnsPlugin.client]
ssrVitePlugins: [TanStackServerFnsPlugin.ssr]
serverVitePlugins: [TanStackServerFnsPlugin.server]

Providing the wrapper implementations

Each runtime replacement should be implemented by your framework. Generally, on the client and SSR runtimes, you'll end up using a fetch call to call the server function your desired endpoint, like this:

function createClientRpc(functionId: string) {
  const url = `${process.env.YOUR_SERVER_BASE}/_server-fn/${functionId}`

  const fn = async (...args: any[]) => {
    const res = await fetch(url, {
      method: 'POST',
      // You'll likely want to use a better serializer here
      body: JSON.stringify(args),
    })

    return await res.json()
  }

  // You can also assign any other properties you want to the function
  // for things like form actions, or debugging
  Object.assign(fn, {
    url: url,
  })

  return fn
}

Using the manifest

In your server handler, you can import the manifest and use it to look up and dynamically import the server function you want to call.

import serverFnManifest from 'tsr:server-fn-manifest'

export const handler = async (req: Request) => {
  const functionId = req.url.split('/').pop()
  invariant(functionId, 'No function ID provided')

  const fnInfo = serverFnManifest[functionId]
  invariant(fn, `Server function ${functionId} not found`)

  const fnModule = await fnInfo.importer()
  invariant(fnModule, `Server function ${functionId} could not be imported`)

  const args = await req.json()

  return await fnModule(...args)