Conditional compilation of dependency feature based on target doesn't work

[PaulGrandperrin]

Here is my use case:
The crate hyper can be compiled with or without SSL.
The target_env gnu compiles fine with SSL whereas musl (for static linking) doesn't.

Here is what I'd like to do:

# By default compile hyper with SSL except when target_env is musl
[target.'cfg(not(target_env = "musl"))'.dependencies]
hyper = {version="*", features=["ssl"], default-features = false}

# When target_env is musl, compile hyper without SSL
[target.'cfg(target_env = "musl")'.dependencies]
hyper = {version="*", default-features = false}

It doesn't work as intented, the hyper/ssl feature compilation is tried whatever the target platform.
I'm using cargo 0.10.0-nightly (4e6434d 2016-03-24).

[alexcrichton]

Hm this is indeed surprising!

I think that this can work, but it doesn't lend itself well to the current implementation. We currently record "activated features" in resolve, but we probably need to delay what was actually activated until the very end when we're compiling crates as that's where the filtering of target-specific dependencies and such actually happens.

[dthul]

Are there any news on this issue?
I have the exact same problem with the "blas" crate. I want to disable its default features on Windows (since they break the build) but use the default features on Linux. My current setup:

[target.'cfg(not(windows))'.dependencies.blas]
version = "0.15.4" # We use the standard options on Linux (meaning building OpenBLAS during compilation)

[target.'cfg(windows)'.dependencies.blas]
version = "0.15.4"
default-features = false # We take care of linking a BLAS implementation on Windows ourselves (see build.rs)

Is there a workaround or do I have to modify Cargo.toml manually according to my target?

[fuine]

I believe I have the same problem, while trying to use specific feature in x11 crate only if a specific feature in my crate is set:

[target.'cfg(feature="my_xss")'.dependencies]
x11 = {version = "2.14", features = ["xlib", "xss"]}
[target.'cfg(not(feature="my_xss"))'.dependencies]
x11 = {version = "2.14", features = ["xlib"]}

[features]
my_xss = []

No matter what features the crate is compiled with, it always compiles x11 with xss feature. Is this supposed to be happening?

[axos88]

I'm also unable to cross-compile my project to both raspberry and x86_64 for testing due to this not working:

[target.'cfg(not(target_arch = "arm"))'.dependencies]
wiringpi = { version = '0.2.4' }

[target.'cfg(target_arch = "arm")'.dependencies]
wiringpi = { version = '0.2.4', features = ["development"] }

The latter would stub the wiringpi libary and just log the usage, which should be good for testing it on my development machine... Currently it doesn't compile because it's looking for a .so file that does not exist for anything other than an arm