serverless express-openapi over netlify functions

operations.js

const usersApi = require("./users");

module.exports = {
  // /users
  "post-users": usersApi.post,
  "get-users": usersApi.get,
  // /users/{userId}
  "get-users-userId": usersApi.get,
  "patch-users-userId": usersApi.patch,
  "delete-users-userId": usersApi.delete,
};

v1.js

const fs = require("fs");
const path = require("path");
const express = require("express");
const expressOpenAPI = require("express-openapi");
const serverless = require("serverless-http");

const apiDocFilename = "./openapi.yaml";
const apiVersion = process.env._HANDLER ? process.env._HANDLER.split(".")[0] : path.basename(__dirname);
const apiDocPath = process.env.LAMBDA_TASK_ROOT ? process.env.LAMBDA_TASK_ROOT : __dirname;
const apiDoc = fs.readFileSync(path.resolve(apiDocPath, apiDocFilename), "utf8");

const operations = require("./operations");

const app = express();

app.use(express.json());

expressOpenAPI.initialize({
  app,
  docsPath: "/docs",
  apiDoc,
  operations,
});

app.use(`/.netlify/functions/${apiVersion}`, app._router);

module.exports = app;
module.exports.handler = serverless(app);

Here's I'm creating a serverless Express.js API that consumes and implements an OpenAPI 3.0 spec using express-openapi over Netlify Functions with the help of serverless-http.

v1.js is my Netlify Function file.
operations.js is the map of operation ids defined in my OpenAPI spec to the Express.js handler.