Remove enforcal of printing exceptions as red

[KristofferC]

The code here

julia/base/errorshow.jl

Lines 87 to 95 in 0413ef0

	function showerror(io::IO, ex, bt; backtrace=true)
	try
	with_output_color(get(io, :color, false) ? error_color() : :nothing, io) do io
	showerror(io, ex)
	end
	finally
	backtrace && show_backtrace(io, bt)
	end
	end

tries its best to ensure that the showerror code an exception implement gets printed in red. This can mess up custom coloring that the exception itself tries to do in showerror. For example, here is some code that defines an exception text using colors:

julia> struct CustomException end

julia> function Base.showerror(io::IO, ce::CustomException)
           printstyled(io, "This is in red\n"; color=:light_red)
           println(io, "This is in white")
       end

Trying with the normal two arg showerror and things look ok. But when the error would actually be shown in REPL, the second line would have "magically" also turned red, ruining the formatting.

If an exception wants to print its text in red, it can just implement that with printstyled.

[JeffBezanson]

I guess just printing ERROR: in red is enough to call attention to it, so I'm fine with that.

[kimikage]

Although I don't feel strongly about it, the fully red messages are somewhat useful when the log is slightly long, and the color is no longer helpful when the log is "very" long.

The coloration is auxiliary function, so I don't think designers of exceptions should specify the colors actively. If desired, you can specify the :normal color

function Base.showerror(io::IO, ce::CustomException)
    printstyled(io, "This is in red\n"; color=:light_red)
    printstyled(io, "This is in white(?)\n"; color=:normal)
end

[KristofferC]

The coloration is auxiliary function, so I don't think designers of exceptions should specify the colors actively.

Why not? Colors can be very useful to improve the clarity of error messages.

If desired, you can specify the :normal color

I know how to work around it. I am saying that trying to color the whole exception message in red is just a bad idea because you don't know how the one that made the error message wants to format it.

[kimikage]

Why not?

Encouraging the designers to customize the color of error messages spoils the simple rule of "red means error".
Unfortunately, I don't think many users read error messages as carefully as you do. 😅

[KristofferC]

Unfortunately, I don't think many users read error messages as carefully as you do. sweat_smile

That seems like an argument to make them better so that people will start reading them? The context this comes up in was when doing error messages for a TOML parser:

compare that with

Also, remember that the Julia error messages used to look like