Start with a colorful log if stderr is TTY, but also respect NO_COLOR

This will ensure we have the same behavior as previous k6 version there's an error before setupLoggers() is executed, e.g. when parsing a wrong CLI flag. However, we will now also respect NO_COLOR and K6_NO_COLOR and disable it when they are specified.

cmd/root.go

@@ -98,7 +98,17 @@ func newGlobalState(ctx context.Context) *globalState {
 	stdOut := &consoleWriter{os.Stdout, colorable.NewColorable(os.Stdout), stdoutTTY, outMutex, nil}
 	stdErr := &consoleWriter{os.Stderr, colorable.NewColorable(os.Stderr), stderrTTY, outMutex, nil}
 
-	logger := getDefaultLogger(stdErr)
+	logger := &logrus.Logger{
+		Out: stdErr,
+		Formatter: &logrus.TextFormatter{
+			ForceColors: stderrTTY,
+			// This is a hack just for this env var, since we need the logger
+			// before we can parse all of the env vars...
+			DisableColors: !stderrTTY || os.Getenv("NO_COLOR") != "" || os.Getenv("K6_NO_COLOR") != "",
+		},
+		Hooks: make(logrus.LevelHooks),
+		Level: logrus.InfoLevel,
+	}
 
 	confDir, err := os.UserConfigDir()
 	if err != nil {
@@ -110,30 +120,26 @@ func newGlobalState(ctx context.Context) *globalState {
 	defaultFlags := getDefaultFlags(confDir)
 
 	return &globalState{
-		ctx:            ctx,
-		fs:             afero.NewOsFs(),
-		getwd:          os.Getwd,
-		args:           append(make([]string, 0, len(os.Args)), os.Args...), // copy
-		envVars:        envVars,
-		defaultFlags:   defaultFlags,
-		flags:          getFlags(defaultFlags, envVars),
-		outMutex:       outMutex,
-		stdOut:         stdOut,
-		stdErr:         stdErr,
-		stdIn:          os.Stdin,
-		signalNotify:   signal.Notify,
-		signalStop:     signal.Stop,
-		logger:         logger,
-		fallbackLogger: getDefaultLogger(stdErr), // we may modify the other one
-	}
-}
-
-func getDefaultLogger(out io.Writer) *logrus.Logger {
-	return &logrus.Logger{
-		Out:       out,
-		Formatter: new(logrus.TextFormatter),
-		Hooks:     make(logrus.LevelHooks),
-		Level:     logrus.InfoLevel,
+		ctx:          ctx,
+		fs:           afero.NewOsFs(),
+		getwd:        os.Getwd,
+		args:         append(make([]string, 0, len(os.Args)), os.Args...), // copy
+		envVars:      envVars,
+		defaultFlags: defaultFlags,
+		flags:        getFlags(defaultFlags, envVars),
+		outMutex:     outMutex,
+		stdOut:       stdOut,
+		stdErr:       stdErr,
+		stdIn:        os.Stdin,
+		signalNotify: signal.Notify,
+		signalStop:   signal.Stop,
+		logger:       logger,
+		fallbackLogger: &logrus.Logger{ // we may modify the other one
+			Out:       stdErr,
+			Formatter: new(logrus.TextFormatter), // no fancy formatting here
+			Hooks:     make(logrus.LevelHooks),
+			Level:     logrus.InfoLevel,
+		},
 	}
 }
 
@@ -163,6 +169,12 @@ func getFlags(defaultFlags globalFlags, env map[string]string) globalFlags {
 	if val, ok := env["K6_LOG_FORMAT"]; ok {
 		result.logFormat = val
 	}
+	if _, ok := env["K6_NO_COLOR"]; ok {
+		result.noColor = true
+	}
+	if _, ok := env["NO_COLOR"]; ok { // https://no-color.org/
+		result.noColor = true
+	}
 	return result
 }