Platform specific dependencies documentation unclear

[gnzlbg]

See here: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html

I depend on two platform specific crates, A and B:

[target.'cfg(foo)'.dependencies]
crate_a = "0.4.0"

[target.'cfg(bar)'.dependencies]
crate_b = "1.0.1"

Crate A has one feature "baz" enabled by default. I want to disable it by default, and then re-export it as my own feature baz.

IIUC I could do this to disable it by default:

[dependencies.crate_a]
default-features = false

• I am not sure whether this works for platform specific dependencies as well, the docs don't say. Cargo produces this warning:

warning: dependency (crate_a) specified without providing a local path, Git repository, or version to use. This will be considered an error in future versions

After I disable all default features of crate A, I have no idea how to re-export them. The docs say I should do:

[features]
baz = [ "crate_a/baz" ] 

but what happens when I am on a target that is using crate_b and crate_a does not exist ? Is that still ok? EDIT: with the fix below it seems to "just work" but I am not sure if this is some behavior I can rely on. Like what happens when someone in a platform that uses crate_b enables the feature baz ?

[gnzlbg]

Ok so it seems that I have to do:

[target.'cfg(foo)'.dependencies.crates_a]
crate_a = "0.4.0"
default-features = false

to disable the features of a platform-specific dependency. An example of this in the docs would have helped.

[gnzlbg]

Maybe related to this #1197 ?

[stale]

As there hasn't been any activity here in over 6 months I've marked this as stale and if no further activity happens for 7 days I will close it.

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[gnzlbg]

Is this still relevant?

Yes.

If so, what is blocking it?

Nothing.

[epage]

Unsure if this would be better in https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html or https://doc.rust-lang.org/cargo/reference/features.html#dependency-features

Its also not quite clear to me what is needing documenting. That default-features = false can be used? That seems like just-another dependency field. @gnzlbg could you help me understand what the point of confusion was.

[weihanglo]

The doc has been improved since then, and this has been stale for a while. Given there is no response from the original author, I am going to close this. Feel free to open a new issue if there are still some confusions.