ReferenceError: __dirname is not defined in ES module scope

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This error occurs when using Prisma in an ES module environment (indicated by .js files in a project with "type": "module" in package.json). The issue is that Prisma's client uses __dirname which isn't available in ES modules.

Solutions:

1. Use moduleFormat = "esm" with prisma-client provider

generator client {
  provider     = "prisma-client"
  output       = "../src/generated/prisma"
  moduleFormat = "esm"
}

This ensures Prisma Client uses import.meta.url instead of __dirname for file path resolution.

2. Create a CommonJS wrapper

import type { PrismaClient as ImportedPrismaClient } from "@prisma/client";
import { createRequire } from "module";

const require = createRequire(import.meta.url);
const { PrismaClient: RequiredPrismaClient } = require("@prisma/client");

const _PrismaClient = RequiredPrismaClient;

export class PrismaClient extends _PrismaClient {}

3. Add a global definition

For build scripts, you can add a global definition of __dirname:

sed -i '1i\globalThis.__dirname = "/";' "node_modules/.../library.js"

4. For Nuxt/SvelteKit projects

In Nuxt, you can add to your config:

build: {
  transpile: ['~/prisma/client'],
}

For SvelteKit, a post-build script can fix the issue:

sed -i '/await server.init/i \
globalThis.__filename = fileURLToPath(import.meta.url); \
globalThis.__dirname = path.dirname(__filename);' build/handler.js

This issue is particularly common in SvelteKit, Nuxt, and other modern frameworks that use ES modules by default.

GitHub Issue #15614
GitHub Issue #20702

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