Compile as ESM from TS using ncc

[nkooman-bzs]

I've been attempting to compile a Node.js project written in TypeScript using ncc.
I am seeing this error:

ReferenceError: __filename is not defined in ES module scope
This file is being treated as an ES module because it has a '.js' file extension and '...\dist\package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.

From what I can tell, this error is a result of references to the typescript module.
Stack traces lead me to this code in TypeScript:
https://github.com/microsoft/TypeScript/blob/6af21a4a3df87e1f9d6218de63a3c36bcee870b0/src/compiler/sys.ts#L1498

I understand that this is not necessarily a concern for this package, but I'm curious if anyone has a ideas for how to workaround this issue.

I have the following code from the documentation:

const config = createConfig({
  http: {
    listen: 8090, // port, UNIX socket or options
  },
  cors: false,
});

const helloWorldEndpoint = defaultEndpointsFactory.build({
  // method: "get" (default) or array ["get", "post", ...]
  input: z.object({
    name: z.string().optional(),
  }),
  output: z.object({
    greetings: z.string(),
  }),
  handler: async ({ input: { name }, options, logger }) => {
    logger.debug("Options:", options); // middlewares provide options
    return { greetings: `Hello, ${name || "World"}. Happy coding!` };
  },
});

const routing: Routing = {
  v1: {
    hello: helloWorldEndpoint,
  },
};

await createServer(config, routing)

This is my tsconfig.json

{
  "compilerOptions": {
    "lib": [],
    "moduleResolution": "bundler",
    "module": "esnext",
    "target": "esnext",
    "isolatedModules": true,
    "esModuleInterop": true,
    "strict": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "baseUrl": ".",
    "paths": {
      "~/*": ["./src/*"]
    },
  }
}

[nkooman-bzs]

After fiddling some more, setting typescript to be external for ncc compilation resolves the issue.
However, this does not feel like a proper solution. I believe this would just push the issue down the road.

[RobinTail]

This file is being treated

which file is it about, @nkooman-bzs ?

[nkooman-bzs]

I have a single index.ts I am compiling with ncc. This results in a index.js file that I run with node index.js. The code it contains is from the example above.
Let me know if you'd like a repro and I can drum one up.

[RobinTail]

Then the message you get is caused by the combination of three reasons, @nkooman-bzs :

• __filename is the CJS shorthand which is not present in ESM
• you are using ncc that bundles everything, including typescript, that contains __filename, and ncc does not transform it accordingly
• the result bundle is treated as ESM because the nearest package.json has type: "module" entry
  • it says that it's located in ..\dist\package.json, so check it out

My advice:

• consider tsup for transforming your Typescript code, or tsx for running your Typescript code;
• or explore ncc documentation on how either:
  • to externalize typescript

    • -e, --external [mod] Skip bundling 'mod'. Can be used many times

  • or enable ESM/CJS interoperation
    • perhaps it's still an issue for ncc

I hope it helps.