Skip to content

Colorize CLI error banner #15408

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
josevalim merged 2 commits into from
May 21, 2026
+9 −3
Merged

Colorize CLI error banner #15408

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
4a0cf6c
Colorize CLI error banner when ANSI is enabled
kevinschweikert May 21, 2026
103a829
refactor: split formatting in banner and rest
kevinschweikert May 21, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 9 additions & 3 deletions lib/elixir/lib/kernel/cli.ex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -99,9 +99,14 @@ defmodule Kernel.CLI do
Shared helper for error formatting on CLI tools.
"""
def format_error(kind, reason, stacktrace) do
{banner, rest} = format_error_parts(kind, reason, stacktrace)
[banner, rest]
end

defp format_error_parts(kind, reason, stacktrace) do
{blamed, stacktrace} = Exception.blame(kind, reason, stacktrace)

iodata =
banner =
case blamed do
%FunctionClauseError{} ->
formatted = Exception.format_banner(kind, reason, stacktrace)
Expand All @@ -112,7 +117,7 @@ defmodule Kernel.CLI do
Exception.format_banner(kind, blamed, stacktrace)
end

[iodata, ?\n, Exception.format_stacktrace(prune_stacktrace(stacktrace))]
{banner, [?\n, Exception.format_stacktrace(prune_stacktrace(stacktrace))]}
end

@doc """
Expand Down Expand Up @@ -179,7 +184,8 @@ defmodule Kernel.CLI do
## Error handling

defp print_error(kind, reason, stacktrace) do
IO.write(:stderr, format_error(kind, reason, stacktrace))
{banner, rest} = format_error_parts(kind, reason, stacktrace)
IO.write(:stderr, [IO.ANSI.format([:red, banner]), rest])
end

defp blame_match(%{match?: true, node: node}), do: blame_ansi(:normal, "+", node)
Expand Down
Loading