Windows / Colors are displayed as codes

[AndyBitz]

I'm on Windows 10 Build 16299.19

I've recently updated from cargo 0.20.0 to 0.22.0 and now I have the following issue.

Colors (especially green) are not displayed correctly under normal circumstances.
When I redirect stdout to a file everything seems to almost work fine.

I've tried this with cargo 0.21.1 and had the same bug.
A VM with the same Windows Version did't have this problem.
An other device with an older windows version did't have this bug until I updated to the current version.

Could the recent cmd.exe change be the problem?

The nightly version has the same bug. Only 0.20.0 seems to work normal.
This is the same for cmd, powershell and hyper (the terminal emulator I use).

I've posted this on StackOverflow before.

[alexcrichton]

Thanks for the report!

@BurntSushi you wouldn't happen to know what's going on here would you? We're using a pretty thin wrapper over the termcolor crate

[AndyBitz]

Yes, termcolor seems to be the problem.
It replaced term after 0.20.0.

But I'm not sure why it only works when stdout is redirected.
It also seems to print wrong color codes when stderr is redirected to stdout.

cargo run --color always > output.txt 2>&1

output.txt

[alexcrichton]

Do you have the TERM environment variable set? If so, do you know what its value is?

[AndyBitz]

Ahhh. It is xterm-256color. Setting it to nothing solves the problem.

[alexcrichton]

Ok that'd explain it! Do you know how come that variable is set? Should Cargo not be interpreting that environment variable?

[retep998]

https://github.com/BurntSushi/ripgrep/blob/2c84825ccbe2d42e0648b56a7d3289c5f5bcb9e5/termcolor/src/lib.rs#L176-L182

If TERM is set, then it will forcefully attempt to use ANSI codes even if the stdout/stderr it is writing to is a windows console. This is clearly the wrong behavior as the correct behavior is to unconditionally use the windows console API as the way to perform colors when stdout/stderr is a windows console. Even if the color choice is set to ColorChoice::AlwaysAnsi, even if TERM is set, stick to the windows console API!

That said, if you are writing to the windows console and you successfully set ENABLE_VIRTUAL_TERMINAL_PROCESSING via SetConsoleMode (or it was already set via GetConsoleMode), then and only then are you allowed to use Microsoft's flavor of ANSI escape codes. The supported escape codes in this case depend on the version of Windows 10, not the TERM environment variable!

[AndyBitz]

@alexcrichton Probably when working with hyper.js.

@retep998 so, termcolor needs to get fixed?

[alexcrichton]

@AndyBitz hm I'm a little confused then as to what's going on, it sounds like you're using a terminal emulator which claims to support ansi escape codes but it doesn't?

[BurntSushi]

I'm also confused. If you're setting TERM to something other than dumb, then you're declaring that your terminal supports ANSI colors.

[retep998]

@BurntSushi If you're writing to the windows console, then you must disregard what TERM says. Unless the console has the ENABLE_VIRTUAL_TERMINAL_PROCESSING mode enabled, ANSI escape codes will never work. This is the chain of logic that should occur:

• Call GetConsoleMode
• If GetConsoleMode fails then use ansi escape codes based on TERM, the ColorChoice, and the name of the pipe.
• If GetConsoleMode succeeds and the current modes already have ENABLE_VIRTUAL_TERMINAL_PROCESSING then use Microsoft flavor escape codes.
• Otherwise call SetConsoleMode with the current modes or'd with ENABLE_VIRTUAL_TERMINAL_PROCESSING.
• If SetConsoleMode succeeds then use Microsoft flavor escape codes.
• Otherwise use the Windows console API for colors.

[AndyBitz]

Sorry for the confusion, I meant that when I worked on hyper the TERM variable (probably) got set globally and was therefore available in every terminal I used which caused cargo to display wrong colors everywhere.

Also I found this in the Microsoft docs, which is as @retep998 says.

[jacobmorzinski]

My own experience: my TERM is set to msys (not set by me, but set by GitHub's old "git shell" CLI package). I haven't yet upgraded to GitHub's new desktop app, because the old "git shell" CLI package is stunningly useful and I don't want to break it. I do confirm that removing TERM restores colors to cargo's windows console output, so I'm glad that I found this thread.

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