Don't compile ansi_term on Windows

[XAMPPRocky]

ansi_term currently doesn't work on 32bit Windows platforms and is not being maintained. clap being dependent by so many crates(mine included) needs to resolve this since there is no maintainer for ansi_term. There are two solutions I can think of.

• clap maintains a forked version of ansi_term.
• clap pulls required functionality of our ansi_term and into it's own module in tree.

[SergioBenitez]

Alternatively, migrate to yansi, a crate I created for Rocket. The API is fairly similar to ansi_term's, so migrating should be very simple. If there's a feature missing in yansi that makes migrating difficult, I'm happy to adjust the API.

[BurntSushi]

@SergioBenitez Your crate only supports ANSI escape sequences, which won't work in Windows consoles that don't have ANSI support. (Your API is also appears fundamentally incompatible with how Windows console coloring works.)

[SergioBenitez]

@BurntSushi Yes, I'm quite aware of that; it's even part of the crate's name! This issue is about moving away from ansi_term, which also doesn't support older Windows consoles.

[BurntSushi]

@SergioBenitez Let me rephrase: It would be great to move to a library that supports Windows console coloring.

[kbknapp]

@Aaronepower ansi_term isn't used by clap on Windows, as I just default to no color support on Windows. However, the plan is to move to termcolor to enable color support for Windows. Progress can be tracked specifically in #836

However, this color re-write will be implemented in v3 (which actively being worked again after a stagnant period) and can be tracked via the overall v3 tracking issue #1037

I've implemented a feature freeze for v2 so I can actually get v3 out the door. So it shouldn't be long before v3-alpha1 is out.

I'm going to close this so comments can be consolidated in one place. I appreciate the suggestions @SergioBenitez and if termcolor ends up not working out and I have to default back to no Windows color support, but still want color support elsewhere I'll look into swapping ansi_term with yansi.

[XAMPPRocky]

@kbknapp It's still compiled on Windows which is the real problem.

[kbknapp]

@Aaronepower Ah, I see my mistake. I'll re-open this issue as "Don't compile ansi_term on Windows which should be totally possible with cargo.

[kbknapp]

I'd be willing to merge a PR for 2.29.3 that fixes this.

[kbknapp]

Turns out this is harder than I had first thought: rust-lang/cargo#1197

[kbknapp]

For those compiling only to windows, not using the color feature will disable compiling ansi_term

kevin@beefcake: ~/Projects/clap-rs 
➜ cargo build --no-default-features --features wrap_help,suggestions
   Compiling strsim v0.7.0
   Compiling libc v0.2.36
   Compiling bitflags v1.0.1
   Compiling unicode-width v0.1.4
   Compiling term_size v0.3.1
   Compiling textwrap v0.9.0
   Compiling clap v2.29.4 (file:///home/kevin/Projects/clap-rs)
    Finished dev [unoptimized + debuginfo] target(s) in 8.0 secs

I'm going to close this for now, and re-address once cargo supports per-target deps. I'll also keep this in mind during the great color redux in v3.

[retep998]

re-address once cargo supports per-target deps

You mean like [target.i686-pc-windows-gnu.dependencies] or [target.'cfg(all(windows, target_arch="x86"))'.dependencies]? Or did you mean per-target features?

[kbknapp]

@retep998 I meant them somewhat interchangeably. The issue being the color feature is currently ignored on Windows, yet even though it's ignored the ansi_term dep is still compiled.

What I'd like to happen is per-target features (so that on everything but Windows the color feature will include ansi_term, but on Windows the color feature will simply be empty, thus not compiling ansi_term for no reason).

If this is already possible, I may have misunderstood the state of things.

[retep998]

While features themselves cannot be target specific, dependencies can, even if they are optional. You can enable the feature from any target, but the dependency will only be compiled for the targets it specifies.

[kbknapp]

TIL...just tested it and it works!

Wow 🎉 Thanks for the explanation @retep998 👍

I'll re-open this and put in the PR.