Refactor LogLevelWithColors into generic structure and test it.

The test added ensures that WithColors behavior matches that which colored itself does. The main reason
we duplicate this behavior is so that we can format without doing any additional allocations.

.travis.yml

@@ -10,8 +10,9 @@ before_script:
 script:
 - cargo build --verbose
 - cargo test --verbose -- --skip test2 --skip test3
-- cargo test test2
-- cargo test test3
+- cargo test --verbose test2
+- cargo test --verbose test3
+- cargo test --verbose --all-features -- --skip test2 --skip test3
 - cargo run --example cmd-program
 - cargo run --example cmd-program -- --verbose
 - cargo run --example colored --features colored

appveyor.yml

@@ -48,8 +48,9 @@ install:
 test_script:
 - cargo build --verbose
 - cargo test --verbose -- --skip test2 --skip test3
-- cargo test test2
-- cargo test test3
+- cargo test --verbose test2
+- cargo test --verbose test3
+- cargo test --verbose --all-features -- --skip test2 --skip test3
 - cargo run --example cmd-program
 - cargo run --example cmd-program -- --verbose
 - cargo run --example colored --features colored

src/colors.rs

@@ -15,22 +15,31 @@ use log::LogLevel;
 /// Extension crate allowing the use of `.colored` on LogLevels.
 trait ColoredLogLevel {
     /// Colors this log level with the given color.
-    fn colored(&self, color: Color) -> LogLevelWithColor;
+    fn colored(&self, color: Color) -> WithFgColor<LogLevel>;
 }
 
-/// Opaque structure representing a log level with an associated color. This implements [`fmt::Display`] so that it is
-/// displayed as the underlying log level surrounded with ASCII markers for the given color.
+/// Opaque structure which represents some text data and a color to display it with. This implements [`fmt::Display`]
+/// via displaying the inner text (usually a log level) with ANSI color markers before to set the color and after to
+/// reset the color.
+///
+/// WithFgColor instances can be created and displayed without any allocation.
 // this is necessary in order to avoid using colored::ColorString, which has a Display
 // implementation involving many allocations, and would involve two more string allocations
 // even to create it.
-pub struct LogLevelWithColor {
-    level: LogLevel,
+pub struct WithFgColor<T>
+where
+    T: fmt::Display,
+{
+    text: T,
     color: Color,
 }
 
-impl fmt::Display for LogLevelWithColor {
+impl<T> fmt::Display for WithFgColor<T>
+where
+    T: fmt::Display,
+{
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "\x1B[{}m{}\x1B[0m", self.color.to_fg_str(), self.level)
+        write!(f, "\x1B[{}m{}\x1B[0m", self.color.to_fg_str(), self.text)
     }
 }
 
@@ -184,7 +193,7 @@ impl ColoredLogLevelConfig {
     /// of support from the [`colored`] crate, this will not function in Windows.
     ///
     /// [`colored`]: https://github.com/mackwic/colored
-    pub fn color(&self, level: LogLevel) -> LogLevelWithColor {
+    pub fn color(&self, level: LogLevel) -> WithFgColor<LogLevel> {
         level.colored(self.get_color(&level))
     }
 
@@ -201,10 +210,50 @@ impl ColoredLogLevelConfig {
 }
 
 impl ColoredLogLevel for LogLevel {
-    fn colored(&self, color: Color) -> LogLevelWithColor {
-        LogLevelWithColor {
-            level: *self,
+    fn colored(&self, color: Color) -> WithFgColor<LogLevel> {
+        WithFgColor {
+            text: *self,
             color: color,
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::WithFgColor;
+    use colored::Colorize;
+    use colored::Color::*;
+
+    #[test]
+    fn fg_color_matches_colored_behavior() {
+        for &color in &[
+            Black,
+            Red,
+            Green,
+            Yellow,
+            Blue,
+            Magenta,
+            Cyan,
+            White,
+            BrightBlack,
+            BrightRed,
+            BrightGreen,
+            BrightYellow,
+            BrightBlue,
+            BrightMagenta,
+            BrightCyan,
+            BrightWhite,
+        ] {
+            assert_eq!(
+                format!("{}", "test".color(color)),
+                format!(
+                    "{}",
+                    WithFgColor {
+                        text: "test",
+                        color: color,
+                    }
+                )
+            );
+        }
+    }
+}