Log color is broken sometimes

[gshuflin]

The decision of whether to use color is made very early in the startup process, while the default value for the --[no-]colors flag is being computed:

pants/src/python/pants/option/global_options.py

Lines 533 to 541 in af5fad7

	register(
	"--colors",
	type=bool,
	default=sys.stdout.isatty(),
	help=(
	"Whether Pants should use colors in output or not. This may also impact whether "
	"some tools Pants run use color."
	),
	)

Instead, the --[no-]colors flag should become a ternary (either explicitly e.g. "yes, no, auto" or implicitly e.g. "true, false, None"), and in case of "auto", we should lazily detect the TTY per destination:

pants/src/rust/engine/logging/src/logger.rs

Lines 198 to 199 in af5fad7

	// TODO: Fix application of color for log-files: see https://github.com/pantsbuild/pants/issues/11020
	let use_color = self.use_color.load(Ordering::SeqCst);

[Eric-Arellano]

I've noticed this. I think it's when pantsd is used. In fact, I don't think colors for the WARN part ever work for me with pantsd.

[stuhood]

The way that we should likely solve this will be shaken up quite a bit by #11536, but it is still an issue.

Post #11536, we should likely convert the --colors flag into a ternary of None/True/False, and move the defaulting of the None case deeper into 1) the Console object at creation time based on stdio (which will have been replaced), and 2) the logging module, which should inspect whether the destination accepts color.

[Eric-Arellano]

we should likely convert the --colors flag into a ternary of None/True/False

What is None here? Auto-detect what to do?

[stuhood]

we should likely convert the --colors flag into a ternary of None/True/False

What is None here? Auto-detect what to do?

Yea. So could convert into an actual ternary... would probably want to do --dynamic-ui at the same time. I didn't see a reason for it before, but the ternary allow us to delay deciding what we're going to do until post-options parsing as we launch the UI, or create a Console.

EDIT: Updated the description with this info.