Backend (NestJS)

The official companion package @tahanabavi/typefetch-nestjs ↗ lets you import the same contracts object on a NestJS backend to bind routes and validate request input and response output against each contract's Zod request/response schemas. One contract, end-to-end type-and-runtime safety — the route can't drift from the client.

Compatible with TypeFetch >= 1.6.0.

Installation

bash

npm i @tahanabavi/typefetch-nestjs @tahanabavi/typefetch zod

Peer dependencies: @nestjs/common, @nestjs/core, rxjs, reflect-metadata, and zod@^4.

Example

import { Controller } from "@nestjs/common";
import {
  TypeFetchEndpoint,
  ContractInput,
  InferRequest,
  InferResponse,
} from "@tahanabavi/typefetch-nestjs";
import { contracts } from "./contracts";

@Controller()
export class UserController {
  @TypeFetchEndpoint(contracts.user.getUser) // GET /users/:id from the contract
  async getUser(
    @ContractInput() input: InferRequest<typeof contracts.user.getUser>,
  ): Promise<InferResponse<typeof contracts.user.getUser>> {
    return { id: input.path.id, name: "Taha" };
  }
}

Core API

Export	Purpose
`@TypeFetchEndpoint(contract)`	Binds the HTTP method and path from the contract and wires request/response validation.
`@UseContract(contract)`	Validation-only decorator for retrofitting existing `@Get`/`@Post` routes.
`@ContractInput()`	Injects the full validated, typed input, shaped exactly like what the client passed.
`@ContractPath()` / `@ContractQuery()` / `@ContractBody()` / `@ContractHeaders()`	Inject an individual validated input section.
`InferRequest<T>` / `InferResponse<T>`	Type helpers for a contract's input and output.
`TypeFetchModule.forRoot({ ... })`	Global options.
`getContractEndpoint(ctx)`	Lets a guard read the contract, e.g. to honor its `auth` flag.

Query and path strings are auto-coerced to the contract's declared types (numbers, booleans, dates, arrays), mirroring the client's URLSearchParams serialization. Validation failures return a RichError-compatible 400 ({ message, code, errors }), so the client's RichError surfaces field errors directly.

Mirrored features

The backend mirrors TypeFetch's client capabilities:

OpenAPI 3.0 / Swagger generation from your contracts (setupContractSwagger, buildOpenApiDocument).
Multipart / file-upload validation for bodyType: "form-data" contracts.
Response envelope matching the client's setResponseWrapper ({ success, data } / { success, message }).
Field-level encryption mirroring encryptionMiddleware — decrypts request fields before validation, encrypts response fields after — byte-compatible via crypto-js/node-forge.

Full documentation lives at @tahanabavi/typefetch-nestjs on GitHub ↗ and on npm ↗.