feature: Make usable without atty.

Cargo.toml

@@ -11,11 +11,13 @@ readme = "README.md"
 keywords = ["color", "string", "term", "ansi_term", "term-painter"]
 
 [features]
+default = ["tty"]
+tty = ["dep:atty"]
 # with this feature, no color will ever be written
 no-color = []
 
 [dependencies]
-atty = "0.2"
+atty = { version = "0.2", optional = true }
 lazy_static = "1"
 
 [target.'cfg(windows)'.dependencies.winapi]

src/control.rs

@@ -103,9 +103,16 @@ impl ShouldColorize {
     /// `CLICOLOR_FORCE` takes highest priority, followed by `NO_COLOR`,
     /// followed by `CLICOLOR` combined with tty check.
     pub fn from_env() -> Self {
+        #[allow(unused_mut)]
+        let mut tty: Option<bool> = None;
+
+        #[cfg(feature = "tty")]
+        {
+            tty = Some(atty::is(atty::Stream::Stdout));
+        }
         ShouldColorize {
-            clicolor: ShouldColorize::normalize_env(env::var("CLICOLOR")).unwrap_or_else(|| true)
-                && atty::is(atty::Stream::Stdout),
+            clicolor: ShouldColorize::normalize_env(env::var("CLICOLOR")).unwrap_or(true)
+                && tty.unwrap_or(false),
             clicolor_force: ShouldColorize::resolve_clicolor_force(
                 env::var("NO_COLOR"),
                 env::var("CLICOLOR_FORCE"),

src/lib.rs

@@ -25,6 +25,7 @@
 //!
 #![warn(missing_docs)]
 
+#[cfg(feature = "tty")]
 extern crate atty;
 #[macro_use]
 extern crate lazy_static;