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fastify-zod-openapi

(★ 122)

Fastify plugin for zod-openapi

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- config.json
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- FUNDING.yml
- release.yml
- renovate.json5
- openapi.ts
- index.ts
- plugin.test.ts
- plugin.ts
- serializerCompiler.test.ts
- serializerCompiler.ts
- transformer.test.ts
- transformer.ts
- validationError.ts
- validatorCompiler.test.ts
- validatorCompiler.ts
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# Installation Guide

1. Get the code

git clone https://github.com/samchungy/fastify-zod-openapi

Downloads the entire project code from GitHub to your computer.

cd fastify-zod-openapi

Moves into the project folder you just downloaded.

2. Node.js

Easy Recommended

Prerequisites

Git Needed to download the project code from GitHub.
Node.js Node.js must be installed to use npm. The LTS version is recommended.

npm install zod fastify-zod-openapi

Downloads and installs the libraries listed in package.json.

yarn add zod fastify-zod-openapi

Type this command into your terminal and run it.

pnpm install zod fastify-zod-openapi

Downloads and installs the libraries listed in package.json.

pnpm install

Downloads and installs the libraries listed in package.json.

pnpm build

Type this command into your terminal and run it.

✅ After running the command, open the address shown in the terminal (usually something like http://localhost:3000) in your browser.

Pulled directly from this repo's README.

// repository documentation

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<p align="center">
  <h1 align="center">fastify-zod-openapi</h1>
</p>
<p align="center">
Fastify <a href="https://fastify.dev/docs/latest/Reference/Type-Providers/">type provider</a>, <a href="https://fastify.dev/docs/latest/Reference/Validation-and-Serialization/">validation, serialization</a> and <a href="https://github.com/fastify/fastify-swagger">@fastify/swagger</a> support for <a href="https://github.com/samchungy/zod-openapi">zod-openapi</a>.
</p>
<div align="center">
<a href="https://www.npmjs.com/package/fastify-zod-openapi"><img src="https://img.shields.io/npm/v/fastify-zod-openapi"/><a>
<a href="https://www.npmjs.com/package/fastify-zod-openapi"><img src="https://img.shields.io/npm/dm/fastify-zod-openapi"/><a>
<a href="https://nodejs.org/en/"><img src="https://img.shields.io/badge/node-%3E%3D%2020-brightgreen"/><a>
<a href="https://github.com/samchungy/fastify-zod-openapi/actions/workflows/test.yml"><img src="https://github.com/samchungy/fastify-zod-openapi/actions/workflows/test.yml/badge.svg"/><a>
<a href="https://github.com/samchungy/fastify-zod-openapi/actions/workflows/release.yml"><img src="https://github.com/samchungy/fastify-zod-openapi/actions/workflows/release.yml/badge.svg"/><a>
<a href="https://github.com/seek-oss/skuba"><img src="https://img.shields.io/badge/🤿%20skuba-powered-009DC4"/><a>
</div>
<br>

## Install

Install via `npm`, `pnpm` or `pnpm`:

```bash
npm install zod fastify-zod-openapi
## or
yarn add zod fastify-zod-openapi
## or
pnpm install zod fastify-zod-openapi
```

## Usage

```ts
import fastify from 'fastify';
import {
  type FastifyZodOpenApiSchema,
  type FastifyZodOpenApiTypeProvider,
  serializerCompiler,
  validatorCompiler,
} from 'fastify-zod-openapi';
import * as z from 'zod/v4';

const app = fastify();

app.setValidatorCompiler(validatorCompiler);
app.setSerializerCompiler(serializerCompiler);

app.withTypeProvider<FastifyZodOpenApiTypeProvider>().route({
  method: 'POST',
  url: '/:jobId',
  schema: {
    body: z.object({
      jobId: z.string().meta({
        description: 'Job ID',
        example: '60002023',
      }),
    }),
    response: {
      201: z.object({
        jobId: z.string().meta({
          description: 'Job ID',
          example: '60002023',
        }),
      }),
    },
  } satisfies FastifyZodOpenApiSchema,
  handler: async (req, res) => {
    await res.send({ jobId: req.body.jobId });
  },
});

await app.ready();
await app.listen({ port: 5000 });
```

## Usage with plugins

```ts
import fastify from 'fastify';
import {
  type FastifyPluginAsyncZodOpenApi,
  type FastifyZodOpenApiSchema,
  serializerCompiler,
  validatorCompiler,
} from 'fastify-zod-openapi';
import * as z from 'zod/v4';

const app = fastify();

app.setValidatorCompiler(validatorCompiler);
app.setSerializerCompiler(serializerCompiler);

const plugin: FastifyPluginAsyncZodOpenApi = async (fastify, _opts) => {
  fastify.route({
    method: 'POST',
    url: '/',
    // Define your schema
    schema: {
      body: z.object({
        jobId: z.string().meta({
          description: 'Job ID',
          example: '60002023',
        }),
      }),
      response: {
        201: z.object({
          jobId: z.string().meta({
            description: 'Job ID',
            example: '60002023',
          }),
        }),
      },
    } satisfies FastifyZodOpenApiSchema,
    handler: async (req, res) => {
      await res.send({ jobId: req.body.jobId });
    },
  });
};

app.register(plugin);
```

## Usage with @fastify/swagger

```ts
import fastifySwagger from '@fastify/swagger';
import fastifySwaggerUI from '@fastify/swagger-ui';
import fastify from 'fastify';
import {
  type FastifyZodOpenApiSchema,
  type FastifyZodOpenApiTypeProvider,
  fastifyZodOpenApiPlugin,
  fastifyZodOpenApiTransformers,
  serializerCompiler,
  validatorCompiler,
} from 'fastify-zod-openapi';
import * as z from 'zod/v4';

const app = fastify();

app.setValidatorCompiler(validatorCompiler);
app.setSerializerCompiler(serializerCompiler);

await app.register(fastifyZodOpenApiPlugin);
await app.register(fastifySwagger, {
  openapi: {
    info: {
      title: 'hello world',
      version: '1.0.0',
    },
    openapi: '3.1.0',
  },
  ...fastifyZodOpenApiTransformers,
});
await app.register(fastifySwaggerUI, {
  routePrefix: '/documentation',
});

app.withTypeProvider<FastifyZodOpenApiTypeProvider>().route({
  method: 'POST',
  url: '/',
  schema: {
    body: z.object({
      jobId: z.string().meta({
        description: 'Job ID',
        example: '60002023',
      }),
    }),
    response: {
      201: {
        content: {
          'application/json': {
            schema: z.object({
              jobId: z.string().meta({
                description: 'Job ID',
                example: '60002023',
              }),
            }),
          },
        },
      },
    },
  } satisfies FastifyZodOpenApiSchema,
  handler: async (_req, res) =>
    res.send({
      jobId: '60002023',
    }),
});
await app.ready();
await app.listen({ port: 5000 });
```

### Declaring Components

This library allows you to easily declare components. As an example:

```typescript
const title = z.string().meta({
  description: 'Job title',
  example: 'My job',
  id: 'jobTitle', // <- new field
});
```

Wherever `title` is used in your request/response schemas across your application, it will instead be created as a reference.

```json
{ "$ref": "#/components/schemas/jobTitle" }
```

For a further dive please follow the documentation [here](https://github.com/samchungy/zod-openapi#creating-components).

If you wish to declare the components manually you will need to do so via the plugin's options. You will also need
to create a custom SerializerCompiler to make use of [fast-json-stringify](https://github.com/fastify/fast-json-stringify).

```ts
const components: ZodOpenApiComponentsObject = { schemas: { mySchema } };
await app.register(fastifyZodOpenApiPlugin, {
  components,
});

const customSerializerCompiler = createSerializerCompiler({
  components,
});
```

Alternatively, you can use `JSON.stringify` instead.

```ts
const customSerializerCompiler = createSerializerCompiler({
  stringify: JSON.stringify,
});
```

By default, this library assumes that if a response schema provided is not a Zod Schema, it is a JSON Schema and will naively pass it straight into `fast-json-stringify`. This will not work in conjunction with Fastify's schema registration.

If you have other routes with response schemas which are not Zod Schemas, you can supply a `fallbackSerializer` to `createSerializerCompiler`.

```ts
const customSerializerCompiler = createSerializerCompiler({
  fallbackSerializer: ({ schema, url, method }) => customSerializer(schema),
});
```

Please note: the `parameters` components do not appear to be supported by the `@fastify/swagger` library.

### Create Document Options

If you wish to use [CreateDocumentOptions](https://github.com/samchungy/zod-openapi#createdocumentoptions), pass it in via the plugin options:

```ts
await app.register(fastifyZodOpenApiPlugin, {
  documentOpts: {
    unionOneOf: true,
  },
});
```

### Custom Response Serializer

The default response serializer `serializerCompiler` uses [fast-json-stringify](https://github.com/fastify/fast-json-stringify). Under the hood, the schema passed to the response is transformed using OpenAPI 3.1.0 and passed to `fast-json-stringify` as a JSON Schema.

If are running into any compatibility issues or wish to restore the previous `JSON.stringify` functionality, you can use the `createSerializerCompiler` function.

```ts
const customSerializerCompiler = createSerializerCompiler({
  stringify: JSON.stringify,
});
```

### Error Handling

By default, `fastify-zod-openapi` emits request validation errors in a similar manner to `fastify` when used in conjunction with it's native JSON Schema error handling.

As an example:

```json
{
  "code": "FST_ERR_VALIDATION",
  "error": "Bad Request",
  "message": "params/jobId Expected number, received string",
  "statusCode": 400
}
```

For responses, it will emit a 500 error along with a vague error which will protect your implementation details

```json
{
  "code": "FST_ERR_RESPONSE_SERIALIZATION",
  "error": "Internal Server Error",
  "message": "Response does not match the schema",
  "statusCode": 500
}
```

To customise this behaviour, you may follow the [fastify error handling](https://fastify.dev/docs/latest/Reference/Validation-and-Serialization/#error-handling) guidance.

#### Request Errors

This library throws a `RequestValidationError` when a request fails to validate against your Zod Schemas

##### setErrorHandler

```ts
fastify.setErrorHandler(function (error, request, reply) {
  if (error.validation) {
    const zodValidationErrors = error.validation.filter(
      (err) => err instanceof RequestValidationError,
    );
    const zodIssues = zodValidationErrors.map((err) => err.params.issue);
    const originalError = zodValidationErrors?.[0]?.params.error;
    return reply.status(422).send({
      zodIssues
      originalError
    });
  }
});
```

##### setSchemaErrorFormatter

```ts
fastify.setSchemaErrorFormatter(function (errors, dataVar) {
  let message = `${dataVar}:`;
  for (const error of errors) {
    if (error instanceof RequestValidationError) {
      message += ` ${error.instancePath} ${error.keyword}`;
    }
  }

return new Error(message);
});

// {
// code: 'FST_ERR_VALIDATION',
// error: 'Bad Request',
// message: 'querystring: /jobId invalid_type',
// statusCode: 400,
// }
```

##### attachValidation

```ts
app.withTypeProvider<FastifyZodOpenApiTypeProvider>().get(
  '/',
  {
    schema: {
      querystring: z.object({
        jobId: z.string().meta({
          description: 'Job ID',
          example: '60002023',
        }),
      }),
    },
    attachValidation: true,
  },
  (req, res) => {
    if (req.validationError?.validation) {
      const zodValidationErrors = req.validationError.validation.filter(
        (err) => err instanceof RequestValidationError,
      );
      console.error(zodValidationErrors);
    }

return res.send(req.query);
  },
);
```

#### Response Errors

```ts
app.setErrorHandler((error, _req, res) => {
  if (error instanceof ResponseSerializationError) {
    return res.status(500).send({
      error: 'Bad response',
    });
  }
});

// {
//   error: 'Bad response';
// }
```

## Credits

[fastify-type-provider-zod](https://github.com/turkerdev/fastify-type-provider-zod): Big kudos to this library for lighting the way with how to create type providers, validators and serializers. fastify-zod-openapi is just an extension to this library whilst adding support for the functionality of zod-openapi.

## Development

### Prerequisites

- Node.js LTS
- pnpm

```shell
pnpm install
pnpm build
```

### Test

```shell
pnpm test
```

### Lint

```shell
# Fix issues
pnpm format

# Check for issues
pnpm lint
```

### Release

To release a new version

1. Create a [new GitHub Release](https://github.com/samchungy/zod-openapi/releases/new)
2. Select `🏷️ Choose a tag`, enter a version number. eg. `v1.2.0` and click `+ Create new tag: vX.X.X on publish`.
3. Click the `Generate release notes` button and adjust the description.
4. Tick the `Set as the latest release` box and click `Publish release`. This will trigger the `Release` workflow.
5. Check the `Pull Requests` tab for a PR labelled `Release vX.X.X`.
6. Click `Merge Pull Request` on that Pull Request to update main with the new package version.

To release a new beta version

1. Create a [new GitHub Release](https://github.com/samchungy/fastify-zod-openapi/releases/new)
2. Select `🏷️ Choose a tag`, enter a version number with a `-beta.X` suffix eg. `v1.2.0-beta.1` and click `+ Create new tag: vX.X.X-beta.X on publish`.
3. Click the `Generate release notes` button and adjust the description.
4. Tick the `Set as a pre-release` box and click `Publish release`. This will trigger the `Prerelease` workflow.