Merge pull request prometheus#14004 from liam-howe-maersk/implement-c…

…onfig-marshal

configuration: Implement IsZero for relabel.Regex to remove default regex

model/relabel/relabel.go

@@ -206,6 +206,11 @@ func (re Regexp) MarshalYAML() (interface{}, error) {
 	return nil, nil
 }
 
+// IsZero implements the yaml.IsZeroer interface.
+func (re Regexp) IsZero() bool {
+	return re.Regexp == DefaultRelabelConfig.Regex.Regexp
+}
+
 // String returns the original string used to compile the regular expression.
 func (re Regexp) String() string {
 	str := re.Regexp.String()

model/relabel/relabel_test.go

@@ -851,3 +851,52 @@ func BenchmarkRelabel(b *testing.B) {
 		})
 	}
 }
+
+func TestConfig_UnmarshalThenMarshal(t *testing.T) {
+	tests := []struct {
+		name      string
+		inputYaml string
+	}{
+		{
+			name: "Values provided",
+			inputYaml: `source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_port]
+separator: ;
+regex: \\d+
+target_label: __meta_kubernetes_pod_container_port_number
+replacement: $1
+action: replace
+`,
+		},
+		{
+			name: "No regex provided",
+			inputYaml: `source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_port]
+separator: ;
+target_label: __meta_kubernetes_pod_container_port_number
+replacement: $1
+action: keepequal
+`,
+		},
+		{
+			name: "Default regex provided",
+			inputYaml: `source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_port]
+separator: ;
+regex: (.*)
+target_label: __meta_kubernetes_pod_container_port_number
+replacement: $1
+action: replace
+`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			unmarshalled := Config{}
+			err := yaml.Unmarshal([]byte(test.inputYaml), &unmarshalled)
+			require.NoError(t, err)
+
+			marshalled, err := yaml.Marshal(&unmarshalled)
+			require.NoError(t, err)
+
+			require.Equal(t, test.inputYaml, string(marshalled))
+		})
+	}
+}