Deno: __dirname / __filename Polyfill

[zekth]

Just an idea to facilitate migrations is to polyfill __dirname and __filename
__dirname can already be polyfilled by using import.meta.url

Edited like @rsp corrected

[rsp]

Deno.cwd() is like process.cwd() in Node, not like __dirname.
It prints the current working directory, not the directory where the script is in.

You'd have to use import.meta.url and location.href for that

[zekth]

Right my test case was wrong but anyway the addition would be nice.

[rsp]

Using something like this will make the same output as Node:

const __filename = new URL(import.meta.url).pathname;
console.log(__filename);

but with Deno the modules doesn't have to have local filenames so it would work only if:
new URL(import.meta.url).protocol === 'file:'
In other cases you might want to leave the full URL.

[rsp]

@zekth inspired by this issue I wrote a simple polyfill and put it on GitHub:

• https://github.com/rsp/deno-dirname

You can use it as:

import { __ } from 'https://deno.land/x/dirname/mod.ts';
const { __filename, __dirname } = __(import.meta);

console.log(__dirname);
console.log(__filename);

[ry]

Seems like @rsp has the solution. Closing.

[balupton]

Would be nice for an official solution to be added to std/node/global.ts.

However, the technique of deno-dirname is not able to be directly compatible, as it requires import.meta.url to be passed as an argument to a function call, as such it serves more as ponyfill than a polyfill.

I've created filedirname which offers greater environment compatibility (Deno, Node.js, CJS, and Web Browsers), and can operate as a direct polyfill. It is what make-deno-edition uses for automatic __filename and __dirname compatibility when creating deno editions from Node.js code.

Further inquiry could be done as to wether the filedirname technique could be added directly into std/node/global.ts, as it does not require any arguments to be passed to it, so could be implemented as a getter or a proxy.

Happy to do a PR if direct implementation is called upon, however as the main value of std/node is from tools like make-deno-edition which already includes support for it, then I'm not sure what the value will be.