Colorize CLI error banner#15408
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josevalim merged 2 commits intoMay 21, 2026
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The script-crash path in Kernel.CLI.print_error/3 now renders the exception banner (e.g. "** (ArgumentError) ...") in red when IO.ANSI.enabled?/0 is true. The stacktrace stays plain. Coloring is opt-in via a new ansi? argument on Kernel.CLI.format_error/4 that defaults to false, so callers that build Mix.Task.Compiler.Diagnostic messages from the same helper keep producing plain text and do not leak escape codes into existing consumers (see elixir-lang#13142). Assisted-by: claude-code:claude-opus-4-7
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This is good to me, we don't need a |
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Thanks for the feedback! I've seperated the different components to color them in the 
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kevinschweikert
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💚 💙 💜 💛 ❤️ |
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I noticed that the error message from the cli output is not colored and thought it would improve readability, when more salient. Hope this improves the overall experience. It's gated behind the
--colorflag to not break existing output parsing.Claude Opus was used to assist in this PR
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