collectors/version: Allow for custom label (#1860)

Co-authored-by: bwplotka <[email protected]>

Author: mrueg

prometheus/collectors/version/version.go

@@ -15,15 +15,44 @@ package version
 
 import (
 	"fmt"
+	"maps"
 
 	"github.com/prometheus/common/version"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+type Option func(*options)
+
+type options struct {
+	extraConstLabels prometheus.Labels
+}
+
+func WithExtraConstLabels(l prometheus.Labels) Option {
+	return func(o *options) {
+		o.extraConstLabels = l
+	}
+}
+
 // NewCollector returns a collector that exports metrics about current version
 // information.
-func NewCollector(program string) prometheus.Collector {
+func NewCollector(program string, opts ...Option) prometheus.Collector {
+	o := options{}
+	for _, opt := range opts {
+		opt(&o)
+	}
+
+	constLabels := prometheus.Labels{
+		"version":   version.Version,
+		"revision":  version.GetRevision(),
+		"branch":    version.Branch,
+		"goversion": version.GoVersion,
+		"goos":      version.GoOS,
+		"goarch":    version.GoArch,
+		"tags":      version.GetTags(),
+	}
+	maps.Copy(constLabels, o.extraConstLabels)
+
 	return prometheus.NewGaugeFunc(
 		prometheus.GaugeOpts{
 			Namespace: program,
@@ -32,15 +61,7 @@ func NewCollector(program string) prometheus.Collector {
 				"A metric with a constant '1' value labeled by version, revision, branch, goversion from which %s was built, and the goos and goarch for the build.",
 				program,
 			),
-			ConstLabels: prometheus.Labels{
-				"version":   version.Version,
-				"revision":  version.GetRevision(),
-				"branch":    version.Branch,
-				"goversion": version.GoVersion,
-				"goos":      version.GoOS,
-				"goarch":    version.GoArch,
-				"tags":      version.GetTags(),
-			},
+			ConstLabels: constLabels,
 		},
 		func() float64 { return 1 },
 	)

prometheus/collectors/version/version_test.go

@@ -0,0 +1,114 @@
+// Copyright 2025 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package version
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var defaultLabels = []string{"branch", "goarch", "goos", "goversion", "revision", "tags", "version"}
+
+func TestGoVersionCollector(t *testing.T) {
+	reg := prometheus.NewPedanticRegistry()
+	reg.MustRegister(NewCollector(
+		"foo"),
+	)
+	result, err := reg.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := json.Marshal(result); err != nil {
+		t.Errorf("json marshalling should not fail, %v", err)
+	}
+
+	got := []string{}
+
+	for _, r := range result {
+		got = append(got, r.GetName())
+		fmt.Println("foo")
+		m := r.GetMetric()
+
+		if len(m) != 1 {
+			t.Errorf("expected 1 metric, but got %d", len(m))
+		}
+
+		lk := []string{}
+		for _, lp := range m[0].GetLabel() {
+			lk = append(lk, lp.GetName())
+		}
+
+		if diff := cmp.Diff(lk, defaultLabels); diff != "" {
+			t.Errorf("missmatch (-want +got):\n%s", diff)
+		}
+
+	}
+
+	if diff := cmp.Diff(got, []string{"foo_build_info"}); diff != "" {
+		t.Errorf("missmatch (-want +got):\n%s", diff)
+	}
+}
+
+func TestGoVersionCollectorWithLabels(t *testing.T) {
+	reg := prometheus.NewPedanticRegistry()
+
+	labels := prometheus.Labels{
+		"z-mylabel": "myvalue",
+	}
+	reg.MustRegister(NewCollector(
+		"foo", WithExtraConstLabels(labels)),
+	)
+	result, err := reg.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := json.Marshal(result); err != nil {
+		t.Errorf("json marshalling should not fail, %v", err)
+	}
+
+	got := []string{}
+
+	for _, r := range result {
+		got = append(got, r.GetName())
+		fmt.Println("foo")
+		m := r.GetMetric()
+
+		if len(m) != 1 {
+			t.Errorf("expected 1 metric, but got %d", len(m))
+		}
+
+		lk := []string{}
+		for _, lp := range m[0].GetLabel() {
+			lk = append(lk, lp.GetName())
+		}
+
+		labels := append(defaultLabels, "z-mylabel")
+
+		if diff := cmp.Diff(lk, labels); diff != "" {
+			t.Errorf("missmatch (-want +got):\n%s", diff)
+		}
+
+	}
+
+	if diff := cmp.Diff(got, []string{"foo_build_info"}); diff != "" {
+		t.Errorf("missmatch (-want +got):\n%s", diff)
+	}
+}