Prisma Extension with Express.js HTTP Request Context

prisma-context.ts

import { Request, Response, NextFunction } from "express";
import { AsyncLocalStorage } from "node:async_hooks";
import { PrismaClient } from '@prisma/client';

const ASYNC_LOCAL_STORAGE = new AsyncLocalStorage();

export const setContext = (callback: (req: Request) => any) => {
  return (req: Request, _res: Response, next: NextFunction) => {
    const context = callback(req);

    // Set context for current request
    ASYNC_LOCAL_STORAGE.run(context, () => {
      next(); // Run next middleware
    });
  };
};

export const prismaWithContext = new PrismaClient().$extends({
  query: {
    $allModels: {
      async $allOperations({ query, args }: any) {
        const context = ASYNC_LOCAL_STORAGE.getStore()

        // Do something with "context"

        // ^ This approach is used by https://github.com/BemiHQ/prisma for automatic
        // database change tracking stitched with customized request-specific context
        // without the need to manually update DB queries or wrap them in transactions

        return query(args)
      },
    },
  },
})

server.ts

import express from "express";
import { setContext } from "./prisma-context";

const app = express();
const port = 3000;

app.use(
  setContext((req: Request) => ({
    userId: req.user?.id,
    apiEndpoint: req.url,
    params: req.body,
  }))
);

app.listen(port, () => {
  console.log(`Server is running on port ${port}`);
}