Fixed colour output being printed to non-TTY outputs & to `NO_COLOR` environments.

This branch is basically done now; merge back to `cli` after patching the colouring code (& merging `ext.rs`) to `master` (and bumping its BF version.)

Fortune for rematch's current commit: Blessing − 吉

Cargo.toml

@@ -29,4 +29,4 @@ clap = { version = "4.5.35", features = ["derive", "env", "string"] }
 regex = { version = "1.11.1", features = ["use_std"] }
 color-eyre = { version = "0.6.3", default-features = false, features = ["track-caller"] }
 rayon = "1.10.0"
-owo-colors = "3.5.0"
+owo-colors = { version = "3.5.0", features = ["alloc", "supports-colors"] }

src/main.rs

@@ -161,6 +161,17 @@ fn main() -> eyre::Result<()>
 
     if args.len() < 4 {
 	use owo_colors::OwoColorize;
+	use owo_colors::Stream;
+
+	macro_rules! colour {
+	    (in $name:ident: $fmt:expr => $col:ident) => {
+		$fmt.if_supports_color(Stream::$name, |text| text.$col())
+	    };
+	    ($fmt:expr => $col:ident) => {
+		colour!(in Stdout: $fmt => $col)
+	    }
+	}
+	
 	println!("rematch v{}: Regular-expression group matcher", env!("CARGO_PKG_VERSION"));
 	println!("");
 	println!("Usage: {} <str> <regex> <group>...", args[0]);
@@ -168,14 +179,14 @@ fn main() -> eyre::Result<()>
 	println!("");
 	println!("Enabled Features:");
 	if cfg!(feature="perl") {
-	    println!("{}\t\t\tEnable PCRE2 (extended) regular-expressions.\n\t\t\tNote that PCRE2 regex engine matches on *bytes*, not *characters*; meaning if a match cuts a vlid UTF8 codepoint into an invalid one, the output will replace the invalid characters with U+FFFD REPLACEMENT CHARACTER.", disjoint!["+", "perl"].bright_red());
+	    println!("{}\t\t\tEnable PCRE2 (extended) regular-expressions.\n\t\t\tNote that PCRE2 regex engine matches on *bytes*, not *characters*; meaning if a match cuts a vlid UTF8 codepoint into an invalid one, the output will replace the invalid characters with U+FFFD REPLACEMENT CHARACTER.", colour!(disjoint!["+", "perl"] => bright_red));
 	} else {
-	    println!("{}\t\t\tPCRE2 (extended) features are disabled; a faster but less featureful regular expression engine (that matches on UTF8 strings instead of raw bytes) is used instead.", disjoint!["-", "perl"].blue());
+	    println!("{}\t\t\tPCRE2 (extended) features are disabled; a faster but less featureful regular expression engine (that matches on UTF8 strings instead of raw bytes) is used instead.", colour!(disjoint!["-", "perl"] => blue));
 	}
 	if cfg!(feature="unstable") {
-	    println!("{}\t\tUnstable optimisations evailable & enabled for build.", disjoint!["+", "unstable"].red());
+	    println!("{}\t\tUnstable optimisations evailable & enabled for build.", colour!(disjoint!["+", "unstable"] => red));
 	} else {
-	    println!("{}\t\tUnstable optimisations disabled / not available for build.", disjoint!["-", "unstable"].bright_blue());
+	    println!("{}\t\tUnstable optimisations disabled / not available for build.", colour!(disjoint!["-", "unstable"] => bright_blue));
 	}
 	std::process::exit(1)
     } else {