Colour output doesn't work in cmd on Windows

[garyb]

It just prints the colour codes as text:

←[34m[info] ←[0mInstalling 65 dependencies.←[0m
←[34m[info] ←[0mSearching for packages cache metadata..←[0m
←[34m[info] ←[0mUnable to find packages cache metadata, downloading from GitHub..←[0m
←[34m[info] ←[0mInstalling "exists"←[0m
←[34m[info] ←[0mInstalling "distributive"←[0m

Perhaps related to #729, but the suggestion there is there's a regression in an upstream library, and it's been this way for as long as I've been using spago. That doesn't necessarily rule out the upstream regression, as I came to it late!

[garyb]

I probably should have mentioned, this isn't true for all commands. The [info] highlight works correctly for builds, for example.

[f-f]

The [info] highlight works correctly for builds, for example.

Oh, that's funny then - if all color was wrong then we'd know that there's something wrong with the lway we do logging, but if only some coloring is wrong then I am not really sure how to even debug this. Do you have any ideas? We're using the logging machinery from RIO

[garyb]

Ah! I think it's something that purs is doing that makes it work actually. Any command that invokes the compiler has colour codes working correctly after "Compiling..." messages have been printed. spago docs is a perfect example actually, because it does this kind of thing:

←[34m[info] ←[0mGenerating documentation for the project. This might take a while...←[0m
Compiling documentation for Data.NaturalTransformation
Compiling documentation for Unsafe.Coerce
Compiling documentation for Record.Unsafe
Compiling documentation for Type.Proxy
... snip ...
Documentation written to: generated-docs/html
[info] Docs generation succeeded.
[info] Making the documentation searchable...

So before the compiler is invoked: no colour, after, colour.

[garyb]

I have an idea of something to try 🙂

[f-f]

Oh I see, that makes sense. Note that we just disable ANSI codes when TERM=win:

spago/src/Spago/RunEnv.hs

Lines 24 to 27 in 72315e0

	-- https://github.com/purescript/spago/issues/579
	maybeTerm <- Env.lookupEnv "TERM"
	let termDumb = maybeTerm == Just "dumb" || maybeTerm == Just "win"
	let useColor = globalUseColor && not termDumb

..but maybe we should just disable it when running on Windows at all?

[stkb]

Yeah would nice to get this fixed. I've tried to do some investigating but it's quite laborious with the little knowledge I have.

I've found though that if you just open start a stack repl in the Spago folder, and then do System.IO.putStrLn "\ESC[31mRED\ESC[0m", then it works. But if you do that within the Spago app itself, it doesn't.

Also about TERM=win, I'm not sure what environments exactly that's for? Because that variable isn't set in vanilla Windows.

[garyb]

I've not yet managed to determine what the difference is between purs and spago that means it works in one place, and not the other, and that invoking purs inside spago will fix it from that point on too.

I was looking into how stdio was configured with utf-8 support, etc. to see if there was something there as it seems like it must be something along those lines, but I've not gotten back to it to try again yet. I'm probably going to try in a fresh CLI app entirely and see if it works "out of the box", and if not, I can maybe figure something out in there then take it back to spago.

[stkb]

I'm probably going to try in a fresh CLI app entirely and see if it works "out of the box"

Yeah that was just what I was trying next, just with stack new testproject and it does indeed work fine there too. But apart from that I'm completely in the dark.

[garyb]

Interesting! When I hacked spago to the point of printing a colour-coded line from its main before it does anything else (before withUtf8 even), it still wasn't displaying correctly.

[stkb]

with stack new testproject and it does indeed work fine there too.

Ok no I have to correct that. It's when running the exe through stack exec that the colors work. Works for a new project, works for Spago. When just running the .exe from the command line, it doesn't (also for a fresh project)

[f-f]

Could it be because the compiler calls IO.hSetBuffering IO.stdout IO.LineBuffering but we don't?

[garyb]

Replicating the IO setup there was the first thing I tried when I hacked my local spago 😄, I tried doing all that explicitly and avoiding withUtf8, and variations on all that without much luck. I really thought it would be the LineBuffering thing when I saw that.

[stkb]

That didn't work but I think it lead me to the right answer :) Just preparing a PR...