UEA-Prodem

node_modules/@trpc/client/skills/superjson/SKILL.md

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+---
+name: superjson
+description: >
+  Configure SuperJSON transformer on both server initTRPC.create({ transformer:
+  superjson }) and every client terminating link (httpBatchLink, httpLink, wsLink,
+  httpSubscriptionLink) to support Date, Map, Set, BigInt over the wire. Transformer
+  must match on both sides. In v11, transformer goes on individual links, not the
+  client constructor.
+type: composition
+library: trpc
+library_version: '11.16.0'
+requires:
+  - server-setup
+  - client-setup
+sources:
+  - www/docs/server/data-transformers.md
+---
+
+# tRPC -- SuperJSON Transformer
+
+## Setup
+
+### 1. Install superjson
+
+```bash
+npm install superjson
+```
+
+### 2. Add to initTRPC on the server
+
+```ts
+// server/trpc.ts
+import { initTRPC } from '@trpc/server';
+import superjson from 'superjson';
+
+const t = initTRPC.create({
+  transformer: superjson,
+});
+
+export const router = t.router;
+export const publicProcedure = t.procedure;
+```
+
+### 3. Add to every terminating link on the client
+
+```ts
+// client.ts
+import { createTRPCClient, httpBatchLink } from '@trpc/client';
+import superjson from 'superjson';
+import type { AppRouter } from './server/trpc';
+
+const client = createTRPCClient<AppRouter>({
+  links: [
+    httpBatchLink({
+      url: 'http://localhost:3000/trpc',
+      transformer: superjson,
+    }),
+  ],
+});
+```
+
+Now Date, Map, Set, BigInt, RegExp, undefined, and other non-JSON types survive the round trip.
+
+## Core Patterns
+
+### SuperJSON with splitLink and Subscriptions
+
+```ts
+import {
+  createTRPCClient,
+  httpBatchLink,
+  httpSubscriptionLink,
+  splitLink,
+} from '@trpc/client';
+import superjson from 'superjson';
+import type { AppRouter } from './server/trpc';
+
+const client = createTRPCClient<AppRouter>({
+  links: [
+    splitLink({
+      condition: (op) => op.type === 'subscription',
+      true: httpSubscriptionLink({
+        url: 'http://localhost:3000/trpc',
+        transformer: superjson,
+      }),
+      false: httpBatchLink({
+        url: 'http://localhost:3000/trpc',
+        transformer: superjson,
+      }),
+    }),
+  ],
+});
+```
+
+Every terminating link in every branch must have `transformer: superjson`.
+
+### SuperJSON with wsLink
+
+```ts
+import { createTRPCClient, createWSClient, wsLink } from '@trpc/client';
+import superjson from 'superjson';
+import type { AppRouter } from './server/trpc';
+
+const wsClient = createWSClient({
+  url: 'ws://localhost:3000',
+});
+
+const client = createTRPCClient<AppRouter>({
+  links: [
+    wsLink<AppRouter>({
+      client: wsClient,
+      transformer: superjson,
+    }),
+  ],
+});
+```
+
+### Returning Dates from Procedures
+
+```ts
+// server
+import { z } from 'zod';
+import { publicProcedure, router } from './trpc';
+
+const appRouter = router({
+  getEvent: publicProcedure
+    .input(z.object({ id: z.string() }))
+    .query(({ input }) => {
+      return {
+        id: input.id,
+        name: 'Launch Party',
+        date: new Date('2025-01-01T00:00:00Z'),
+      };
+    }),
+});
+
+export type AppRouter = typeof appRouter;
+```
+
+```ts
+// client
+const event = await client.getEvent.query({ id: '1' });
+console.log(event.date instanceof Date); // true
+console.log(event.date.getFullYear()); // 2025
+```
+
+Without superjson, `event.date` would be a string like `"2025-01-01T00:00:00.000Z"`.
+
+## Common Mistakes
+
+### [CRITICAL] Transformer on server but missing from client link
+
+Wrong:
+
+```ts
+// Server
+const t = initTRPC.create({ transformer: superjson });
+
+// Client
+const client = createTRPCClient<AppRouter>({
+  links: [httpBatchLink({ url: 'http://localhost:3000/trpc' })],
+});
+```
+
+Correct:
+
+```ts
+// Server
+const t = initTRPC.create({ transformer: superjson });
+
+// Client
+const client = createTRPCClient<AppRouter>({
+  links: [
+    httpBatchLink({
+      url: 'http://localhost:3000/trpc',
+      transformer: superjson,
+    }),
+  ],
+});
+```
+
+Server encodes with superjson but client tries to parse raw JSON, causing "Unable to transform response" or garbled data.
+
+Source: www/docs/server/data-transformers.md
+
+### [CRITICAL] Transformer goes on individual links, not createTRPCClient
+
+The `transformer` option is on individual terminating links:
+
+```ts
+createTRPCClient<AppRouter>({
+  links: [
+    httpBatchLink({
+      url: 'http://localhost:3000/trpc',
+      transformer: superjson,
+    }),
+  ],
+});
+```
+
+In v11, `transformer` was moved from the client constructor to individual links. Passing it to `createTRPCClient` throws a TypeError.
+
+Source: packages/client/src/internals/TRPCUntypedClient.ts
+
+### [CRITICAL] Transformer on only some terminating links in splitLink
+
+Wrong:
+
+```ts
+splitLink({
+  condition: (op) => op.type === 'subscription',
+  true: httpSubscriptionLink({
+    url: 'http://localhost:3000/trpc',
+    // missing transformer!
+  }),
+  false: httpBatchLink({
+    url: 'http://localhost:3000/trpc',
+    transformer: superjson,
+  }),
+});
+```
+
+Correct:
+
+```ts
+splitLink({
+  condition: (op) => op.type === 'subscription',
+  true: httpSubscriptionLink({
+    url: 'http://localhost:3000/trpc',
+    transformer: superjson,
+  }),
+  false: httpBatchLink({
+    url: 'http://localhost:3000/trpc',
+    transformer: superjson,
+  }),
+});
+```
+
+Every terminating link must have the same transformer. A missing transformer on one branch causes deserialization failures only for operations routed through that branch.
+
+Source: www/docs/server/data-transformers.md
+
+### [HIGH] Using transformer on client but not on server
+
+Wrong:
+
+```ts
+// Server -- no transformer
+const t = initTRPC.create();
+
+// Client
+httpBatchLink({ url, transformer: superjson });
+```
+
+Correct:
+
+```ts
+// Server
+const t = initTRPC.create({ transformer: superjson });
+
+// Client
+httpBatchLink({ url, transformer: superjson });
+```
+
+The transformer must be configured on both `initTRPC.create()` and every client link. Client-only transformer corrupts the request encoding because the server expects plain JSON.
+
+Source: www/docs/server/data-transformers.md
+
+## See Also
+
+- `client-setup` -- create the tRPC client and configure links
+- `links` -- detailed options for each link type including transformer
+- `server-setup` -- initTRPC.create() where the server transformer is configured