feat(server + client): add support for server-sent events (SSE) (#5713)

Author: KATT

src/client/index.ts

@@ -1,7 +1,12 @@
 /**
  * This is the client-side code that uses the inferred types from the server
  */
-import { createTRPCClient, unstable_httpBatchStreamLink } from '@trpc/client';
+import {
+  createTRPCClient,
+  splitLink,
+  unstable_httpBatchStreamLink,
+  unstable_httpSubscriptionLink,
+} from '@trpc/client';
 /**
  * We only import the `AppRouter` type from the server - this is not available at runtime
  */
@@ -10,8 +15,14 @@ import type { AppRouter } from '../server/index.js';
 // Initialize the tRPC client
 const trpc = createTRPCClient<AppRouter>({
   links: [
-    unstable_httpBatchStreamLink({
-      url: 'http://localhost:3000',
+    splitLink({
+      condition: (op) => op.type === 'subscription',
+      true: unstable_httpSubscriptionLink({
+        url: 'http://localhost:3000',
+      }),
+      false: unstable_httpBatchStreamLink({
+        url: 'http://localhost:3000',
+      }),
     }),
   ],
 });

src/server/index.ts

@@ -2,6 +2,7 @@
  * This a minimal tRPC server
  */
 import { createHTTPServer } from '@trpc/server/adapters/standalone';
+import { observable } from '@trpc/server/observable';
 import { z } from 'zod';
 import { db } from './db.js';
 import { publicProcedure, router } from './trpc.js';

src/server/trpc.ts

@@ -4,11 +4,7 @@ import { initTRPC } from '@trpc/server';
  * Initialization of tRPC backend
  * Should be done only once per backend!
  */
-const t = initTRPC.create({
-  experimental: {
-    iterablesAndDeferreds: true,
-  },
-});
+const t = initTRPC.create();
 
 /**
  * Export reusable router and procedure helpers