extract-openapi-req

A lightweight TypeScript library for extracting OpenAPI metadata from HTTP requests. This package helps you easily extract and validate request metadata against your OpenAPI specifications.

Features

• 🚀 Load OpenAPI specs from URL or object
• 🔍 Extract OpenAPI metadata and path parameters
• ✨ Match request paths against OpenAPI paths
• 📘 Full TypeScript support
• 🪶 Zero dependencies (except path-to-regexp)
• 🔌 Framework agnostic design

Installation

npm install extract-openapi-req

Usage

import { OpenApiExtractor } from "extract-openapi-req";

// Initialize the extractor
const extractor = new OpenApiExtractor();

// Load spec from URL
await extractor.loadSpec("https://api.example.com/openapi.json");

// Or load from object
await extractor.loadSpec(require("./openapi.json"));

// Extract metadata from a request
const metadata = extractor.extract("/v1/users/123", "GET");

if (metadata) {
  console.log("Operation ID:", metadata.schema.operationId);
  console.log("Path Parameters:", metadata.params);
  console.log("Full Operation Schema:", metadata.schema);
}

Framework Integration Examples

Hono (Built-in Middleware)

import { Hono } from "hono";
import { OpenApiExtractor } from "extract-openapi-req";
import {
  createHonoMiddleware,
  HonoOpenApiVariables,
} from "extract-openapi-req/frameworks/hono";

const app = new Hono<{ Variables: HonoOpenApiVariables }>();
const extractor = new OpenApiExtractor();

// Load OpenAPI spec
await extractor.loadSpec(openApiSpec);

// Add the middleware
const middleware = createHonoMiddleware(extractor);
app.use("*", middleware);

// Access OpenAPI metadata in your handlers
app.get("/users/:id", (c) => {
  const metadata = c.get("openapi");
  // Use the metadata...
});

Express

import express from "express";
import { OpenApiExtractor } from "extract-openapi-req";

const app = express();
const extractor = new OpenApiExtractor();
await extractor.loadSpec("./openapi.json");

app.use((req, res, next) => {
  const metadata = extractor.extract(req.path, req.method);
  if (metadata) {
    req.openapi = metadata;
  }
  next();
});

API Reference

OpenApiExtractor

Methods

• loadSpec(specOrUrl: string | object): Promise<void>
  Load an OpenAPI specification from a URL or object.

• getSpec(): object | null
  Get the currently loaded OpenAPI specification.

• extract(path: string, method: string): OpenApiRequestMetadata | null
  Extract OpenAPI metadata from a request path and method.

Framework Middlewares

Hono

• createHonoMiddleware(extractor: OpenApiExtractor): MiddlewareHandler
  Creates a Hono middleware that automatically extracts and attaches OpenAPI metadata to the request context.

Types

interface OpenApiRequestMetadata {
  schema: OpenAPIV3.OperationObject; // Full OpenAPI operation object
  params: Record<string, string>; // Extracted path parameters
}

type HonoOpenApiVariables = {
  openapi: OpenApiRequestMetadata;
};

Roadmap

Check out our roadmap for upcoming features:

• OpenAPI 2.0 & 3.1.x support
• More prebuilt framework middlewares (Express, Fastify, etc.)
• Better error messages and debugging
• Request/Response validation

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT © ahmedrowaihi