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Terminal colors for output #636

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9999years
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@9999years 9999years commented Dec 12, 2024

This adds terminal colors to cabal2nix's output. This checks if stderr isatty so that output will not be colored if (for example) cabal2nix's stderr is being piped to a file. It also respects the $NO_COLOR and $FORCE_COLOR environment variables for toggling the output coloring (see no-color.org).

A couple small changes while I was preparing this:

  1. I added nix-prefetch-scripts to the shell.nix so that you can run cabal2nix successfully while hacking on it.
  2. I added a line to print the fetcher command (like nix-prefetch-git ...) before we run it. This makes it a lot clearer where the errors come from, and which errors are being ignored (because we're trying another fetcher).

Example output:
image

If stderr isatty (i.e. the output is not being pumped to a file) and
`$NO_COLOR` is unset or empty, or if `$FORCE_COLOR` is set and
non-empty, output is colored.

This helps distinguish `cabal2nix`'s output from the output of the
fetchers it runs.
@sternenseemann
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Good idea, I think this is a good migitation for the error message problem the current fetcher logic has!

Not quite sure what to think about colored output, i.e. if the extra code is worth it…

@9999years
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@sternenseemann Happy to remove the colored output if you'd prefer (or you can update my branch -- just drop the last commit), let me know

@sternenseemann sternenseemann changed the title Print commands before we run them + terminal colors for output Terminal colors for output Dec 16, 2024
@sternenseemann
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I've merged those changes manually, we can leave this PR for the color changes. I'm going to keep thinking about it. Maybe @maralorn and @cdepillabout want to comment?

@cdepillabout
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cdepillabout commented Dec 17, 2024

I think I'm generally in favor of (optional) colors.

For CLI programs that use color, I think I'd also expect a --color / --no-color CLI flag to exist, but I don't think not having it should necessarily block this PR.

@9999years could you post a screenshot of what the colors look like in the output of cabal2nix?

@9999years
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@cdepillabout Added a screenshot to the PR description!

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I think the colors seems nice, and it will likely make visually parsing the output of cabal2nix easier. I'm for merging this.

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3 participants