NO_COLOR is printing ansi in non-terminals

[Boshen]

Background: oxc-project/oxc#3539

Currently, if you use oxc_diagnostics with GraphicalReportHandler, and you print to a non-terminal, the output will contain color escape codes, even with NO_COLOR=1. This is because if stdout or stderr are not a terminal, GraphicalTheme::default() will return GraphicalTheme::ascii() regardless of the NO_COLOR value, and ascii() does have colors. This means that when printing to a non-terminal, there is no way to turn off the color escapes.

When printing to a non-terminal, you usually don't want color output, so presumably the default GraphicalTheme on non-terminals should be GraphicalTheme::none(). But in some cases it might be useful to enable color, even if not by default. Maybe FORCE_COLOR could be used in that case.

miette/src/handlers/theme.rs

Lines 72 to 75 in b82cc81

	match std::env::var("NO_COLOR") {
	_ if !std::io::stdout().is_terminal() || !std::io::stderr().is_terminal() => {
	Self::ascii()
	}

When it's non-terminal, Self::ascii()

miette/src/handlers/theme.rs

Lines 25 to 31 in b82cc81

	/// ASCII-art-based graphical drawing, with ANSI styling.
	pub fn ascii() -> Self {
	Self {
	characters: ThemeCharacters::ascii(),
	styles: ThemeStyles::ansi(),
	}
	}

still uses ansi colors.

If the intention of NO_COLOR is to always not print ansi color codes, I can PR a change to GraphicalTheme::none().

[zkat]

yeah uh, that seems like a bug.