Dependency specifiers akin to PEP 508 from Python

[thernstig]

Problem

Often I want to install a package where I wished the package declared a subset of dependencies to be installed as well.

Python and PEP 508 solves this. See also https://packaging.python.org/en/latest/specifications/dependency-specifiers/#dependency-specifiers.

An example of this can be seen here:

pip install diffusers["torch"]

The ["torch"] part tells us to install diffusers with a subset of tools, in this case also torch.

A real-world use case

https://github.com/socketio/socket.io/ depends on the ws package. But the Node.js API now includes a WebSocket implementation of its own.

If I could then specify this:

npm install socket.io[no-ws]

I could skip that extra package and use the built-in one instead, without having to pollute my node_modules/ with unnecessary packages.

Is this a good or bad idea for an RFCS?

[kylerneva]

npm already handles this through optionalDependencies, peerDependencies, and runtime feature detection, which allows packages to adapt to different environments without adding new install syntax or increasing dependency resolution complexity.

[thernstig]

There is no "optional peerDependency" is there?

How do you achieve PEP 508 to work fine in a project? I cannot see how it is achievable right now.

[ljharb]

Yes, there is. You add the peer dep, and then in a parallel object "peerDependenciesMeta", you specify the dep name and the value as an object with "optional: true".

I have no idea because nobody outside Python ever knows or cares about PEPs. However, if I understand the OP correctly, you want (either, or both?) a package author/consumer to be able to get "not 100% of the production deps specified" installed. No, that's not possible - if you have such subsets, then your package is too big and should be broken up into smaller packages.

[thernstig]

@ljharb I think I explained it sufficiently in the original post. See A real-world use case.

if you have such subsets, then your package is too big and should be broken up into smaller packages

That does not help in the example in the original post, or even if it did, it is not user friendly.

[ljharb]

That's right - you have to ask the maintainer to do it, or, you have to use another package.

[thernstig]

@ljharb if I understand you correct, your stance is that everything is fine as-is. My stance is that this would be good addition.

I have no idea because nobody outside Python ever knows or cares about PEPs

You do. It is just named differently here. Here we call it RFCs.