Add no-default-feature = true to environment definition

[pavelzw]

Problem description

[project]
channels = ["conda-forge", "nvidia"]
platforms = ["linux-64", "win-64"]

[dependencies]
pytorch = "*"

[feature.lint]
channels = ["conda-forge"]
platforms = ["linux-64"]
[feature.lint.dependencies]
pre-commit = "*"

[feature.ruff]
platforms = ["linux-aarch64"]
[feature.ruff.dependencies]
ruff = "*"

[environments]
default = ["test"]
lint = {features = ["lint", "ruff"], no-default-feature = true}

This results in the following lint environment:

• channels = ["conda-forge"] (union of channels from used features) (maybe there is a better solution for this?)
• dependencies: ruff = "*", pre-commit = "*"
• platforms = ["linux-aarch64", "linux-64"] (union of all platforms from used features) (maybe there is a better solution for this?)

I know originally I was opposed to this idea since you can represent this using an empty default feature set but I came to realize that this use actually happens quite often and restricting myself to an empty default feature set just because of this is annoying 😅

WDYT? cc @0xbe7a

[baszalmstra]

Haha I like it.

[0xbe7a]

Yes, I think the use case is pretty common and the "no default feature(s)" behavior is pretty intuitive. I don't understand why it's called "no-default-feature_s_" though? As far as I understand it, it only excludes the single implicit "default" feature from the environment, not multiple features, right?

[pavelzw]

Yes, you're right. no-default-feature would be better :)

[tdejager]

There's a reason cargo has it 😄