Cargo: Optional dependencies cannot enable features

Created on 21 Aug 2015 · 3Comments · Source: rust-lang/cargo

In crate X, with an optional dependency A and a mandatory dependency B of X, the feature A associated to the former cannot enable a feature with the same name in B. This means an additional feature bearing a different name must be introduced, making things messy.

Source

nox

Most helpful comment

I’ve also found it confusing that features and (optional?) dependencies share the same namespace.

SimonSapin on 21 Aug 2015

👍3

All 3 comments

Use case:

I am adding SIMD optimisations to rust-encoding. I want the feature to be named "simd" and to enable the same feature in the internal crate encoding-types.

[features]
simd = ["encoding-types/enable-simd"]

[dependencies.simd]
git = "https://github.com/nox/simd"
rev = "438780ca236b1ed2caf032edebda9c9362eaabc6"
optional = true

This won't work because you can't have an optional dependency and a feature bear the same name.

nox on 21 Aug 2015

I’ve also found it confusing that features and (optional?) dependencies share the same namespace.

SimonSapin on 21 Aug 2015

👍3

Yeah for now you'll have to choose a separate feature name to activate features and dependencies, otherwise though this is covered by #1286 so I'm going to close in favor of that.