Welcome to next-swagger-doc 👋

Generate Swagger JSON API from NextJS Api Routes

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Prerequisites

• Nextjs >= 9
• Node >= 18

Motivation

This package reads your JSDoc-annotated source code on NextJS API route and generates an OpenAPI (Swagger) specification.

nextjs + swagger-jsdoc = next-swagger-doc

Install

yarn add next-swagger-doc

Usage #1: next-swagger-doc with Next.js 13

To incorporate next-swagger-doc with your Next.js 13 project, follow these steps. This setup will generate Swagger documentation for your API based on your code and provide a built-in Swagger UI for viewing the documentation.

1. Create Swagger Spec

Next, create a new file lib/swagger.ts. This file uses the next-swagger-doc library to create a Swagger specification based on the API routes in your Next.js project.

import { createSwaggerSpec } from "next-swagger-doc";

export const getApiDocs = async () => {
  const spec = createSwaggerSpec({
    apiFolder: "app/api", // define api folder under app folder
    definition: {
      openapi: "3.0.0",
      info: {
        title: "Next Swagger API Example",
        version: "1.0",
      },
      components: {
        securitySchemes: {
          BearerAuth: {
            type: "http",
            scheme: "bearer",
            bearerFormat: "JWT",
          },
        },
      },
      security: [],
    },
  });
  return spec;
};

2. Create Swagger UI Component

Generate a new file named app/api-doc/react-swagger.tsx. In this file, create and export a React component that utilizes the swagger-ui-react library to render the Swagger UI according to the provided specification.

For demonstration purposes, here is an example using swagger-ui-react

Feel free to employ any alternative swagger UI library, such as stoplightio/elements. I have added an example using this library in the example folder.

'use client';

import SwaggerUI from 'swagger-ui-react';
import 'swagger-ui-react/swagger-ui.css';

type Props = {
  spec: Record<string, any>,
};

function ReactSwagger({ spec }: Props) {
  return <SwaggerUI spec={spec} />;
}

export default ReactSwagger;

3. Create API Documentation Page

Create a new file app/api-doc/page.tsx. This page imports the Swagger spec and the Swagger UI component to display the Swagger documentation.

import { getApiDocs } from "@/lib/swagger";
import ReactSwagger from "./react-swagger";

export default async function IndexPage() {
  const spec = await getApiDocs();
  return (
    <section className="container">
      <ReactSwagger spec={spec} />
    </section>
  );
}

4. Add Swagger Comment to API Route

Lastly, add a Swagger comment to your API route in app/api/hello/route.ts. This comment includes metadata about the API endpoint which will be read by next-swagger-doc and included in the Swagger spec.

/**
 * @swagger
 * /api/hello:
 *   get:
 *     description: Returns the hello world
 *     responses:
 *       200:
 *         description: Hello World!
 */
export async function GET(_request: Request) {
  // Do whatever you want
  return new Response('Hello World!', {
    status: 200,
  });
}

Now, navigate to localhost:3000/api-doc (or wherever you host your Next.js application), and you should see the swagger UI.

Usage #2: Create an single API document

yarn add next-swagger-doc swagger-ui-react

• Create an live swagger page, e.g: pages/api-doc.tsx

import { GetStaticProps, InferGetStaticPropsType } from 'next';
import { createSwaggerSpec } from 'next-swagger-doc';
import dynamic from 'next/dynamic';
import 'swagger-ui-react/swagger-ui.css';

const SwaggerUI = dynamic<{
  spec: any;
}>(import('swagger-ui-react'), { ssr: false });

function ApiDoc({ spec }: InferGetStaticPropsType<typeof getStaticProps>) {
  return <SwaggerUI spec={spec} />;
}

export const getStaticProps: GetStaticProps = async () => {
  const spec: Record<string, any> = createSwaggerSpec({
    apiFolder: 'pages/api' // or 'src/pages/api',
    definition: {
      openapi: '3.0.0',
      info: {
        title: 'Next Swagger API Example',
        version: '1.0',
      },
    },
  });

  return {
    props: {
      spec,
    },
  };
};

export default ApiDoc;

Usage #3: Use NextJS API route to create Swagger JSON spec

• Step 1: Create an api route on nextjs, e.g: pages/api/doc.ts

import { withSwagger } from "next-swagger-doc";

const swaggerHandler = withSwagger({
  definition: {
    openapi: "3.0.0",
    info: {
      title: "NextJS Swagger",
      version: "0.1.0",
    },
  },
  apiFolder: "pages/api",
});
export default swaggerHandler();

• Step 2: Add JSdoc to any NextJS API routes, for example: pages/api/hello.ts

import { NextApiRequest, NextApiResponse } from "next";

/**
 * @swagger
 * /api/hello:
 *   get:
 *     description: Returns the hello world
 *     responses:
 *       200:
 *         description: hello world
 */
const handler = (_req: NextApiRequest, res: NextApiResponse) => {
  res.status(200).json({
    result: "hello world",
  });
};

export default handler;

• Step 3: Access the Swagger API doc

Usage #4: Generate Swagger file from CLI

• Step 1: create a JSON config file as next-swagger-doc.json

{
  "apiFolder": "pages/api",
  "schemaFolders": ["models"],
  "definition": {
    "openapi": "3.0.0",
    "info": {
      "title": "Next Swagger API Example",
      "version": "1.0"
    }
  }
}

• Step 2: run cli for generating swagger file

yarn next-swagger-doc-cli next-swagger-doc.json

Run example app

gh repo clone jellydn/next-swagger-doc
cd examples/next14-app
pnpm install
pnm run dev

Then open http://localhost:3000/api-doc or http://localhost:3000/ on your browser

Linter

In order to set an eslint rule that checks that all the APIs actually have a swagger JsDoc description we can use the following settings:

Install the JsDoc eslint plugin:

yarn add -D eslint-plugin-jsdoc

Create the custom rule in your eslint configuration file:

{
    //...your configuration
    "overrides": [
        //...your overrides
        {
            // Force the setting of a swagger description on each api endpoint
            "files": ["pages/api/**/*.ts"],
            "plugins": ["jsdoc"],
            "rules": {
                "jsdoc/no-missing-syntax": [
                "error",
                {
                    "contexts": [
                    {
                        "comment": "JsdocBlock:has(JsdocTag[tag=swagger])",
                        "context": "any",
                        "message": "@swagger documentation is required on each API. Check this out for syntax info: https://github.com/jellydn/next-swagger-doc"
                    }
                    ]
                }
            ]
        }
    ]
}

Pre-commit hook

This project uses pre-commit to enforce code quality. To install pre-commit hooks, run:

pre-commit install

Author

👤 Huynh Duc Dung

• Website: https://productsway.com/
• Twitter: @jellydn
• Github: @jellydn

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