Add method to remove labels with empty values

model/labelset.go

@@ -27,6 +27,15 @@ import (
 // match.
 type LabelSet map[LabelName]LabelValue
 
+// RemoveEmptyLabels removes labels that have empty values.
+func (ls LabelSet) RemoveEmptyLabels() {
+	for k, v := range ls {
+		if string(v) == "" {
+			delete(ls, k)
+		}
+	}
+}
+
 // Validate checks whether all names and values in the label set
 // are valid.
 func (ls LabelSet) Validate() error {

model/labelset_test.go

@@ -0,0 +1,21 @@
+package model
+
+import "testing"
+
+func TestRemoveEmptyLabels(t *testing.T) {
+	ls := LabelSet{
+		LabelName("one"):   LabelValue("two"),
+		LabelName("three"): LabelValue("four"),
+		LabelName("five"):  LabelValue(""),
+	}
+
+	ls.RemoveEmptyLabels()
+
+	if _, prs := ls["five"]; prs {
+		t.Errorf(`key "five" not removed from map`)
+	}
+
+	if len(ls) != 2 {
+		t.Errorf("expected 2 keys in labelset; found %d:\n%v\n", len(ls), ls)
+	}
+}