zod-openapi-share

zod-openapi-share is an extension package for @hono/zod-openapi that lets you centralize and reuse response definitions across endpoints. Normally, @hono/zod-openapi requires you to redefine the same responses (e.g., error schemas) for every endpoint, but with zod-openapi-share, you can avoid repetition and prevent definition drift, making your backend development using hono + @hono/zod-openapi cleaner and more consistent.

What is zod-openapi-share?

In projects using hono, you may have opportunities to use a convenient package called @hono/zod-openapi as middleware for generating OpenAPI schemas. This package allows you to define both OpenAPI schemas and Zod-based validation at the same time.

However, it has a major drawback: you must repeatedly write out the responses definitions for every single status code across all endpoints. In many cases, error responses share the exact same structure across endpoints — yet, even if they are identical, you still have to duplicate those definitions.

To solve this, zod-openapi-share provides a way to centralize and reuse response definitions by wrapping around @hono/zod-openapi. Think of zod-openapi-share as an extension package for @hono/zod-openapi. When using it, you’ll need three packages together: hono, @hono/zod-openapi, and zod-openapi-share.

By unifying response definitions, you can develop without worrying about unintended inconsistencies between endpoints. If you’re using hono and @hono/zod-openapi, be sure to try zod-openapi-share!

import { z, createRoute } from '@hono/zod-openapi';

// Commonly Used Response Schema
const ContentlyStatusCodeArray = [
  100, 102, 103, 200, 201, 202, 203, 206, 207, 208, 226, 300, 301, 302, 303, 305, 306, 307, 308, 400, 401, 402, 403,
  404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 421, 422, 423, 424, 425, 426, 428, 429,
  431, 451, 500, 501, 502, 503, 504, 505, 506, 507, 508, 510, 511, -1,
] as const;

export const errorResponseSchema = z.object({
  status: z.union(ContentlyStatusCodeArray.map((code) => z.literal(code))).meta({
    example: 400,
    description: 'HTTP Status Code',
  }),
  message: z.string().min(1).meta({
    example: 'Bad Request',
    description: 'Error Message',
  }),
});

// Get Request Sample
const rootGetResponseBodySchema = z.object({
  result: z.string().meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Get Response',
  }),
});

const rootGetRoute = createRoute({
  path: '/',
  method: 'get',
  description: 'Sample Endpoint',
  responses: {
    200: {
      description: 'OK',
      content: {
        'application/json': {
          schema: rootGetResponseBodySchema,
        },
      },
    },
    //** Despite having the same definition, it must be defined repeatedly for each endpoint! */
    // >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> //
    400: {
      description: 'Bad Request',
      content: { 'application/json': { schema: errorResponseSchema } },
    },
    500: {
      description: 'Internal Server Error',
      content: { 'application/json': { schema: errorResponseSchema } },
    },
    // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< //
  },
});

// Post Request Sample
const rootPostRequestBodySchema = z.object({
  input: z.string().min(1).max(100).meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Post Request',
  }),
});

const rootPostResponseBodySchema = z.object({
  result: z.string().meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Post Response',
  }),
});

const rootPostRoute = createRoute({
  path: '/',
  method: 'post',
  description: 'Sample Endpoint',
  request: {
    body: {
      required: true,
      content: {
        'application/json': {
          schema: rootPostRequestBodySchema,
        },
      },
    },
  },
  responses: {
    200: {
      description: 'OK',
      content: {
        'application/json': {
          schema: rootPostResponseBodySchema,
        },
      },
    },
    //** Despite having the same definition, it must be defined repeatedly for each endpoint! */
    // >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> //
    400: {
      description: 'Bad Request',
      content: { 'application/json': { schema: errorResponseSchema } },
    },
    500: {
      description: 'Internal Server Error',
      content: { 'application/json': { schema: errorResponseSchema } },
    },
    // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< //
  },
});

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import { z } from '@hono/zod-openapi';
import { ZodOpenAPISchema } from 'zod-openapi-share';

// Commonly Used Response Schema
const ContentlyStatusCodeArray = [
  100, 102, 103, 200, 201, 202, 203, 206, 207, 208, 226, 300, 301, 302, 303, 305, 306, 307, 308, 400, 401, 402, 403,
  404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 421, 422, 423, 424, 425, 426, 428, 429,
  431, 451, 500, 501, 502, 503, 504, 505, 506, 507, 508, 510, 511, -1,
] as const;

export const errorResponseSchema = z.object({
  status: z.union(ContentlyStatusCodeArray.map((code) => z.literal(code))).meta({
    example: 400,
    description: 'HTTP Status Code',
  }),
  message: z.string().min(1).meta({
    example: 'Bad Request',
    description: 'Error Message',
  }),
});

// Shared Responses Using ZodOpenAPISchema
const route = new ZodOpenAPISchema({
  400: {
    description: 'Bad Request',
    content: { 'application/json': { schema: errorResponseSchema } },
  },
  500: {
    description: 'Internal Server Error',
    content: { 'application/json': { schema: errorResponseSchema } },
  },
} as const);

// Get Request Sample
const rootGetResponseBodySchema = z.object({
  result: z.string().meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Get Response',
  }),
});

const rootGetRoute = route.createSchema(
  {
    path: '/',
    method: 'get',
    description: 'Sample Endpoint',
    responses: {
      200: {
        description: 'OK',
        content: {
          'application/json': {
            schema: rootGetResponseBodySchema,
          },
        },
      },
    },
  },
  // You only need to describe the status codes of the response definitions shared in the array as the second argument!
  [400, 500]
);

// Post Request Sample
const rootPostRequestBodySchema = z.object({
  input: z.string().min(1).max(100).meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Post Request',
  }),
});

const rootPostResponseBodySchema = z.object({
  result: z.string().meta({
    example: 'Hello, World!',
    description: 'Root Endpoint Post Response',
  }),
});

const rootPostRoute = route.createSchema(
  {
    path: '/',
    method: 'post',
    description: 'Sample Endpoint',
    request: {
      body: {
        required: true,
        content: {
          'application/json': {
            schema: rootPostRequestBodySchema,
          },
        },
      },
    },
    responses: {
      200: {
        description: 'OK',
        content: {
          'application/json': {
            schema: rootPostResponseBodySchema,
          },
        },
      },
    },
  }, // You only need to describe the status codes of the response definitions shared in the array as the second argument!
  [400, 500]
);
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How to Use

Examples Here

• cloudflare workers example

  • https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/cloudflare-workers/

• nodejs example

  • https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/

1. Install Packages

npm install hono @hono/zod-openapi zod-openapi-share
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2. Create Zod Schema and ZodOpenAPISchema Class Instance

• Example

https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/src/app/share.ts

import { z } from '@hono/zod-openapi';
import { ZodOpenAPISchema } from 'zod-openapi-share';

const ContentlyStatusCodeArray = [
  100, 102, 103, 200, 201, 202, 203, 206, 207, 208, 226, 300, 301, 302, 303, 305, 306, 307, 308, 400, 401, 402, 403,
  404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 421, 422, 423, 424, 425, 426, 428, 429,
  431, 451, 500, 501, 502, 503, 504, 505, 506, 507, 508, 510, 511, -1,
] as const;

// Zod Schema for Error Response
export const errorResponseSchema = z.object({
  status: z.union(ContentlyStatusCodeArray.map((code) => z.literal(code))).meta({
    example: 400,
    description: 'HTTP Status Code',
  }),
  message: z.string().min(1).meta({
    example: 'Bad Request',
    description: 'Error Message',
  }),
});

export type ErrorResponseSchemaType = z.infer<typeof errorResponseSchema>;

// ZodOpenAPISchema Instance
/**
 * Define Shared Responses Here
 */
export const route = new ZodOpenAPISchema({
  400: {
    description: 'Bad Request',
    content: { 'application/json': { schema: errorResponseSchema } },
  },
  500: {
    description: 'Internal Server Error',
    content: { 'application/json': { schema: errorResponseSchema } },
  },
} as const);

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3. Create RouteConfig Type Object

• createSchema Method

When you want to learn how to use createRoute, please refer to the @hono/zod-openapi.

zodOpenAPISchemaInstance.createSchema(
    createRoute object (@hono/zod-openapi RouteConfig type object),
    StatusCode[] (Array of status codes to be shared from ZodOpenAPISchema instance)
);
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• Example

https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/src/app/route.ts

import { z } from '@hono/zod-openapi';
import { route } from './share.js';

const responseBodySchema = z.object({
  result: z.string().meta({
    example: 'Hello World!',
    description: 'Sample Endpoint Response',
  }),
});

export const rootRoute = route.createSchema(
  {
    path: '/',
    method: 'get',
    description: 'Sample Endpoint',
    responses: {
      200: {
        description: 'OK',
        content: {
          'application/json': {
            schema: responseBodySchema,
          },
        },
      },
    },
  },
  [400, 500]
);

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4. Insert root Variable Into Hono app Instance

• Example

https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/src/app/index.ts

import { OpenAPIHono } from '@hono/zod-openapi';
import { cors } from 'hono/cors';
import { HTTPException } from 'hono/http-exception';
import { type ErrorResponseSchemaType } from './share.js';
import { rootRoute } from './route.js';
import { Scalar } from '@scalar/hono-api-reference';

export const api = () => {
  const app = new OpenAPIHono({
    // Zod Validation Error Hook
    defaultHook: (result) => {
      if (!result.success) {
        console.error(result.error);
        throw new HTTPException(400, {
          message: 'Zod Validation Error',
        });
      }
    },
  });

  // 404 Not Found Handler
  app.notFound((c) => {
    console.error(`Not Found: ${c.req.url}`);
    return c.json({ status: 404, message: 'Not Found' } satisfies ErrorResponseSchemaType, 404);
  });
  // Other Error Handler
  app.onError((error, c) => {
    if (error instanceof HTTPException) {
      return c.json(
        {
          status: error.status,
          message: error.message,
        } satisfies ErrorResponseSchemaType,
        error.status
      );
    }
    return c.json(
      {
        status: 500,
        message: 'Internal Server Error',
      } satisfies ErrorResponseSchemaType,
      500
    );
  });

  // Settings of CORS
  app.use('*', cors());

  // OpenAPI Document Endpoint
  app.doc('/openapi', {
    openapi: '3.1.0',
    info: {
      title: 'Echo API',
      version: '1.0.0',
      description: 'An example of OpenAPI with hono, @hono/zod-openapi, and zod-openapi-share.',
    },
  });

  // Scalar Web UI Endpoint
  // References
  // https://guides.scalar.com/scalar/scalar-api-references/integrations/hono
  app.get('/scalar', Scalar({ url: '/openapi' }));

  /**
   * Add route to app instance
   */
  app.openapi(rootRoute, (c) => {
    return c.json({ result: 'Hello World!' });
  });

  return app;
};

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5. Define serve (Define Entry Point)

• Example

https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/src/index.ts

import { serve } from '@hono/node-server';
import { api } from './app/index.js';

serve(
  {
    fetch: api().fetch,
    port: 3000,
  },
  (info) => {
    console.log(`Server is running on http://localhost:${info.port}`);
  }
);

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6. Define Generate OpenAPI Document Program

• Example

https://github.com/Myxogastria0808/zod-openapi-share/tree/main/examples/nodejs/src/openapi.ts

import { api } from './app/index.js';
import fs from 'node:fs';

const docs = api().getOpenAPI31Document({
  openapi: '3.1.0',
  info: {
    title: 'hono + @hono/zod-openapi + zod-openapi-share sample',
    version: '1.0.0',
    description: 'This is a sample project to generate OpenAPI documents with Hono and Zod.',
  },
});

const json = JSON.stringify(docs, null, 2);

fs.writeFileSync('./openapi.json', json);
console.log(json);

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7. Add generate openapi.json scripts to package.json

• Example

{
  "name": "example",
  "type": "module",
  "private": true,
    "scripts": {
    "dev": "tsx watch src/index.ts",
    "build": "tsc",
    "start": "node dist/index.js",
    "openapi": "tsx src/openapi.ts" // Add this script for generating OpenAPI document
  },
  // [Omitted]
}
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HTML Documentation Generated by typedoc

https://myxogastria0808.github.io/zod-openapi-share/

Test Coverage Generated by @vitest/coverage-v8

https://myxogastria0808.github.io/zod-openapi-share/coverage/

Test Result Generated by @vitest/ui

https://myxogastria0808.github.io/zod-openapi-share/html/

DeepWiki

https://deepwiki.com/Myxogastria0808/zod-openapi-share/