HTTP RPC Specification

import { initTRPC } from '@trpc/server';
const t = initTRPC.create();
const router = t.router;
const publicProcedure = t.procedure;
// ---cut---
export const appRouter = router({
  post: router({
    byId: publicProcedure.input(String).query(async (opts) => {
      // [...]
    }),
  }),
});

import { initTRPC } from '@trpc/server';

type Post = { id: string; title: string; body: string };
type Context = {
  post: { findUnique: (opts: { where: { id: string } }) => Promise<Post | null> };
  findRelatedPostsById: (id: string) => Promise<Post[]>;
};

const t = initTRPC.context<Context>().create();
// ---cut---
export const appRouter = t.router({
  postById: t.procedure.input(String).query(async (opts) => {
    const post = await opts.ctx.post.findUnique({
      where: { id: opts.input },
    });
    return post;
  }),
  relatedPosts: t.procedure.input(String).query(async (opts) => {
    const posts = await opts.ctx.findRelatedPostsById(opts.input);
    return posts;
  }),
});

// @jsx: react-jsx
import React from 'react';

const trpc = null as any;

// ---cut---
export function MyComponent() {
  const post1 = trpc.postById.useQuery('1');
  const relatedPosts = trpc.relatedPosts.useQuery('1');

  return (
    <pre>
      {JSON.stringify(
        {
          post1: post1.data ?? null,
          relatedPosts: relatedPosts.data ?? null,
        },
        null,
        4,
      )}
    </pre>
  );
}

encodeURIComponent(
  JSON.stringify({
    0: '1', // <-- input for `postById`
    1: '1', // <-- input for `relatedPosts`
  }),
);

[
  // result for `postById`
  {
    "result": {
      "data": {
        "id": "1",
        "title": "Hello tRPC",
        "body": "..."
        // ...
      }
    }
  },
  // result for `relatedPosts`
  {
    "result": {
      "data": [
        /* ... */
      ]
    }
  }
]

{
  "result": {
    "data": {
      "id": "1",
      "title": "Hello tRPC",
      "body": "..."
    }
  }
}

type TOutput = any;
// ---cut---
interface SuccessResponse {
  result: {
    data: TOutput; // output from procedure
  }
}

[
  {
    "error": {
      "json": {
        "message": "Something went wrong",
        "code": -32600, // JSON-RPC 2.0 code
        "data": {
          // Extra, customizable, meta data
          "code": "INTERNAL_SERVER_ERROR",
          "httpStatus": 500,
          "stack": "...",
          "path": "post.add"
        }
      }
    }
  }
]

const HTTP_STATUS_CODES = {
  PARSE_ERROR: 400,
  BAD_REQUEST: 400,
  UNAUTHORIZED: 401,
  PAYMENT_REQUIRED: 402,
  FORBIDDEN: 403,
  NOT_FOUND: 404,
  METHOD_NOT_SUPPORTED: 405,
  TIMEOUT: 408,
  CONFLICT: 409,
  PRECONDITION_FAILED: 412,
  PAYLOAD_TOO_LARGE: 413,
  UNSUPPORTED_MEDIA_TYPE: 415,
  UNPROCESSABLE_CONTENT: 422,
  PRECONDITION_REQUIRED: 428,
  TOO_MANY_REQUESTS: 429,
  CLIENT_CLOSED_REQUEST: 499,
  INTERNAL_SERVER_ERROR: 500,
  NOT_IMPLEMENTED: 501,
  BAD_GATEWAY: 502,
  SERVICE_UNAVAILABLE: 503,
  GATEWAY_TIMEOUT: 504,
} as const;

/**
 * JSON-RPC 2.0 Error codes
 *
 * `-32000` to `-32099` are reserved for implementation-defined server-errors.
 * For tRPC we're copying the last digits of HTTP 4XX errors.
 */
export const TRPC_ERROR_CODES_BY_KEY = {
  /**
   * Invalid JSON was received by the server.
   * An error occurred on the server while parsing the JSON text.
   */
  PARSE_ERROR: -32700,
  /**
   * The JSON sent is not a valid Request object.
   */
  BAD_REQUEST: -32600, // 400

  // Internal JSON-RPC error
  INTERNAL_SERVER_ERROR: -32603, // 500
  NOT_IMPLEMENTED: -32603, // 501
  BAD_GATEWAY: -32603, // 502
  SERVICE_UNAVAILABLE: -32603, // 503
  GATEWAY_TIMEOUT: -32603, // 504

  // Implementation specific errors
  UNAUTHORIZED: -32001, // 401
  PAYMENT_REQUIRED: -32002, // 402
  FORBIDDEN: -32003, // 403
  NOT_FOUND: -32004, // 404
  METHOD_NOT_SUPPORTED: -32005, // 405
  TIMEOUT: -32008, // 408
  CONFLICT: -32009, // 409
  PRECONDITION_FAILED: -32012, // 412
  PAYLOAD_TOO_LARGE: -32013, // 413
  UNSUPPORTED_MEDIA_TYPE: -32015, // 415
  UNPROCESSABLE_CONTENT: -32022, // 422
  PRECONDITION_REQUIRED: -32028, // 428
  TOO_MANY_REQUESTS: -32029, // 429
  CLIENT_CLOSED_REQUEST: -32099, // 499
} as const;

import { initTRPC } from '@trpc/server';
import { createHTTPHandler } from '@trpc/server/adapters/standalone';
const t = initTRPC.create();
const router = t.router({});
// ---cut---
// Your server must separately allow the client to override the HTTP method
const handler = createHTTPHandler({
  router: router,
  allowMethodOverride: true,
});

// @filename: server.ts
import { initTRPC } from '@trpc/server';
const t = initTRPC.create();
export const appRouter = t.router({});
export type AppRouter = typeof appRouter;

// @filename: client.ts
// ---cut---
import { createTRPCClient, httpLink } from '@trpc/client';
import type { AppRouter } from './server';

// The client can then specify which HTTP method to use for all queries/mutations
const client = createTRPCClient<AppRouter>({
  links: [
    httpLink({
      url: `http://localhost:3000`,
      methodOverride: 'POST', // all queries and mutations will be sent to the tRPC Server as POST requests.
    }),
  ],
});