Make unit an optional argument in MetricFamilyToOpenMetrics func

Signed-off-by: Arianna Vespri <[email protected]>

Author: vesari

expfmt/openmetrics_create.go

@@ -63,7 +63,25 @@ import (
 //
 //   - The value of Counters is not checked. (OpenMetrics doesn't allow counters
 //     with a `NaN` value.)
-func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int, err error) {
+
+type ToOpenMetrics struct {
+	withUnit bool
+	// withCreated bool can be added in the future
+}
+
+type ToOpenMetricsOption = func(*ToOpenMetrics)
+
+func ToOpenMetricsWithUnit() ToOpenMetricsOption {
+	return func(om *ToOpenMetrics) {
+		om.withUnit = true
+	}
+}
+
+func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily, options ...ToOpenMetricsOption) (written int, err error) {
+	toOM := ToOpenMetrics{}
+	for _, option := range options {
+		option(&toOM)
+	}
 	name := in.GetName()
 	if name == "" {
 		return 0, fmt.Errorf("MetricFamily has no name: %s", in)
@@ -154,7 +172,7 @@ func MetricFamilyToOpenMetrics(out io.Writer, in *dto.MetricFamily) (written int
 	if err != nil {
 		return
 	}
-	if in.Unit != nil {
+	if toOM.withUnit && in.Unit != nil {
 		n, err = w.WriteString("# UNIT ")
 		written += n
 		if err != nil {