UEA-Prodem

node_modules/@trpc/server/skills/adapter-express/SKILL.md

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+---
+name: adapter-express
+description: >
+  Mount tRPC as Express middleware with createExpressMiddleware() from
+  @trpc/server/adapters/express. Access Express req/res in createContext via
+  CreateExpressContextOptions. Mount at a path prefix like app.use('/trpc', ...).
+  Avoid global express.json() conflicting with tRPC body parsing for FormData.
+type: core
+library: trpc
+library_version: '11.16.0'
+requires:
+  - server-setup
+sources:
+  - www/docs/server/adapters/express.md
+  - examples/express-server/src/server.ts
+---
+
+# tRPC — Adapter: Express
+
+## Setup
+
+```ts
+// server.ts
+import { initTRPC } from '@trpc/server';
+import * as trpcExpress from '@trpc/server/adapters/express';
+import express from 'express';
+import { z } from 'zod';
+
+const createContext = ({
+  req,
+  res,
+}: trpcExpress.CreateExpressContextOptions) => {
+  return { req, res };
+};
+type Context = Awaited<ReturnType<typeof createContext>>;
+
+const t = initTRPC.context<Context>().create();
+
+const appRouter = t.router({
+  greet: t.procedure
+    .input(z.object({ name: z.string() }))
+    .query(({ input }) => ({ greeting: `Hello, ${input.name}!` })),
+});
+
+export type AppRouter = typeof appRouter;
+
+const app = express();
+
+app.use(
+  '/trpc',
+  trpcExpress.createExpressMiddleware({
+    router: appRouter,
+    createContext,
+  }),
+);
+
+app.listen(4000, () => {
+  console.log('Listening on http://localhost:4000');
+});
+```
+
+## Core Patterns
+
+### Accessing Express req/res in context
+
+```ts
+import * as trpcExpress from '@trpc/server/adapters/express';
+
+const createContext = ({
+  req,
+  res,
+}: trpcExpress.CreateExpressContextOptions) => {
+  const token = req.headers.authorization?.split(' ')[1];
+  return { token, res };
+};
+
+type Context = Awaited<ReturnType<typeof createContext>>;
+```
+
+`CreateExpressContextOptions` provides typed access to the Express `req` (IncomingMessage) and `res` (ServerResponse).
+
+### Adding tRPC alongside existing Express routes
+
+```ts
+import * as trpcExpress from '@trpc/server/adapters/express';
+import cors from 'cors';
+import express from 'express';
+import { createContext } from './context';
+import { appRouter } from './router';
+
+const app = express();
+
+app.use(cors());
+
+app.get('/health', (_req, res) => {
+  res.json({ status: 'ok' });
+});
+
+app.use(
+  '/trpc',
+  trpcExpress.createExpressMiddleware({
+    router: appRouter,
+    createContext,
+  }),
+);
+
+app.listen(4000);
+```
+
+### Limiting batch size with maxBatchSize
+
+```ts
+import * as trpcExpress from '@trpc/server/adapters/express';
+import express from 'express';
+import { createContext } from './context';
+import { appRouter } from './router';
+
+const app = express();
+
+app.use(
+  '/trpc',
+  trpcExpress.createExpressMiddleware({
+    router: appRouter,
+    createContext,
+    maxBatchSize: 10,
+  }),
+);
+
+app.listen(4000);
+```
+
+Requests batching more than `maxBatchSize` operations are rejected with a `400 Bad Request` error. Set `maxItems` on your client's `httpBatchLink` to the same value to avoid exceeding the limit.
+
+## Common Mistakes
+
+### HIGH Global express.json() consuming tRPC request body
+
+Wrong:
+
+```ts
+const app = express();
+app.use(express.json()); // global body parser
+app.use(
+  '/trpc',
+  trpcExpress.createExpressMiddleware({
+    router: appRouter,
+    createContext,
+  }),
+);
+```
+
+Correct:
+
+```ts
+const app = express();
+// Only apply body parser to non-tRPC routes
+app.use('/api', express.json());
+app.use(
+  '/trpc',
+  trpcExpress.createExpressMiddleware({
+    router: appRouter,
+    createContext,
+  }),
+);
+```
+
+If `express.json()` is applied globally before the tRPC middleware, it consumes and parses the request body. tRPC then receives an already-parsed body, which breaks FormData and binary content type handling.
+
+Source: www/docs/server/non-json-content-types.md
+
+## See Also
+
+- **server-setup** -- `initTRPC.create()`, router/procedure definition, context
+- **adapter-standalone** -- simpler adapter when Express middleware ecosystem is not needed
+- **auth** -- extracting JWT from `req.headers.authorization` in context
+- Express docs: https://expressjs.com/en/guide/using-middleware.html