honor CLICOLOR and CLICOLOR_FORCE

src/encode/writer/console.rs

@@ -4,6 +4,8 @@
 
 use std::{fmt, io};
 
+use once_cell::sync::Lazy;
+
 use crate::encode::{self, Style};
 use once_cell::sync::Lazy;
 
@@ -42,6 +44,43 @@ pub enum ColorMode {
     Never,
 }
 
+#[cfg(not(windows))]
+static COLOR_MODE: Lazy<ColorMode> = Lazy::new(|| {
+    let no_color = std::env::var("NO_COLOR")
+        .map(|var| var != "0")
+        .unwrap_or(false);
+    let clicolor_force = std::env::var("CLICOLOR_FORCE")
+        .map(|var| var != "0")
+        .unwrap_or(false);
+    if no_color {
+        ColorMode::Never
+    }
+    else if clicolor_force {
+        ColorMode::Always
+    } else {
+        let clicolor = std::env::var("CLICOLOR")
+            .map(|var| var != "0")
+            .unwrap_or(true);
+        if clicolor {
+            ColorMode::Auto
+        } else {
+            ColorMode::Never
+        }
+    }
+});
+
+/// The color output mode for a `ConsoleAppender`
+#[derive(Clone, Copy, Default)]
+pub enum ColorMode {
+    /// Print color only if the output is recognized as a console
+    #[default]
+    Auto,
+    /// Force color output
+    Always,
+    /// Never print color
+    Never,
+}
+
 /// An `encode::Write`r that outputs to a console.
 pub struct ConsoleWriter(imp::Writer);