ASCII color codes are displayed inline for editors about proc-macro2-diagnostics HOT 3 OPEN

Right, this is problematic.

The issue, as you identified in rust-lang/rust-analyzer#15443, is that as far as I can tell, there's no way for a proc-macro to know if it should emit colors or not. The proxy is typically to check whether we're connected to a TTY, but Cargo captures all output, so we're never connected to a TTY, and detecting via this manner would mean never emitting colors, which would be a shame.

Ideally, there would be some way to query 1) whether cargo itself will be emitting colors and/or 2) what message-format is expected. Alternatively, if we could inquire about how the compiler is invoked, we might be able to patch this minimally for rust-analyzer. It doesn't seem like 1) or 2) are viable options now, but the alternative might be, given that rust-analyzer appears to set RUSTC_WRAPPER to rust-analyzer by default. If we can detect this, we can stop emitting colors when rust-analyzer invokes rustc.

I'll give this a try now.

from proc-macro2-diagnostics.

Following-up: the above didn't work. First, the wrapper is only set for build scripts, which is fine-ish as we can forward the env-var along via Cargo. Second, and more importantly, the wrapper is only set the first time the build script is built/run, so the solution only really works once in a given workspace, if it works at all.

Until there's some reliable mechanism to detect whether we should color, I think the "correct" solution here is for rust-analyzer to strip ANSI escapes from any output before it re-emits it. Cargo itself uses https://crates.io/crates/strip-ansi-escapes, which is why using --color=never works as expected.

from proc-macro2-diagnostics.

Right. I'm glad you see the issue here. Too bad it does not sound like there is an easy fix around the corner.

Would you mind posting an issue to rust-analyzer or commenting on the issue I posted? I feel like I was unsuccessful convincing them before, so it's probably better to give them your perspective on this.

from proc-macro2-diagnostics.