Add ability to only colorize the header, not the whole log message

colorize_unix.go

@@ -1,3 +1,4 @@
+//go:build !windows
 // +build !windows
 
 package hclog
@@ -21,6 +22,7 @@ func (l *intLogger) setColorization(opts *LoggerOptions) {
 		isCygwinTerm := isatty.IsCygwinTerminal(fi.Fd())
 		isTerm := isUnixTerm || isCygwinTerm
 		if !isTerm {
+			l.headerColor = ColorOff
 			l.writer.color = ColorOff
 		}
 	}

colorize_windows.go

@@ -1,3 +1,4 @@
+//go:build windows
 // +build windows
 
 package hclog
@@ -26,8 +27,12 @@ func (l *intLogger) setColorization(opts *LoggerOptions) {
 		isTerm := isUnixTerm || isCygwinTerm
 		if !isTerm {
 			l.writer.color = ColorOff
+			l.headerColor = ColorOff
 			return
 		}
-		l.writer.w = colorable.NewColorable(fi)
+
+		if l.headerColor == ColorOff {
+			l.writer.w = colorable.NewColorable(fi)
+		}
 	}
 }

intlogger.go

@@ -69,6 +69,8 @@ type intLogger struct {
 	writer *writer
 	level  *int32
 
+	headerColor ColorOption
+
 	implied []interface{}
 
 	exclude func(level Level, msg string, args ...interface{}) bool
@@ -113,17 +115,28 @@ func newLogger(opts *LoggerOptions) *intLogger {
 		mutex = new(sync.Mutex)
 	}
 
+	var primaryColor, headerColor ColorOption
+
+	if opts.ColorHeaderOnly {
+		primaryColor = ColorOff
+		headerColor = opts.Color
+	} else {
+		primaryColor = opts.Color
+		headerColor = ColorOff
+	}
+
 	l := &intLogger{
 		json:              opts.JSONFormat,
 		name:              opts.Name,
 		timeFormat:        TimeFormat,
 		timeFn:            time.Now,
 		disableTime:       opts.DisableTime,
 		mutex:             mutex,
-		writer:            newWriter(output, opts.Color),
+		writer:            newWriter(output, primaryColor),
 		level:             new(int32),
 		exclude:           opts.Exclude,
 		independentLevels: opts.IndependentLevels,
+		headerColor:       headerColor,
 	}
 	if opts.IncludeLocation {
 		l.callerOffset = offsetIntLogger + opts.AdditionalLocationOffset
@@ -232,7 +245,12 @@ func (l *intLogger) logPlain(t time.Time, name string, level Level, msg string,
 
 	s, ok := _levelToBracket[level]
 	if ok {
-		l.writer.WriteString(s)
+		if l.headerColor != ColorOff {
+			color := _levelToColor[level]
+			color.Fprint(l.writer, s)
+		} else {
+			l.writer.WriteString(s)
+		}
 	} else {
 		l.writer.WriteString("[?????]")
 	}

logger.go

@@ -271,6 +271,9 @@ type LoggerOptions struct {
 	// are concretely instances of *os.File.
 	Color ColorOption
 
+	// Only color the header, not the body. This can help with readability of long messages.
+	ColorHeaderOnly bool
+
 	// A function which is called with the log information and if it returns true the value
 	// should not be logged.
 	// This is useful when interacting with a system that you wish to suppress the log