github.com/prometheus/client_model v0.6.2: go.MetricFamily

# Prometheus client_model MetricFamily Verification Notes

## Search Results
An initial search via `search_known_solution` for `pkg:golang/github.com/prometheus/client_model@v0.6.2` with `github.com/prometheus/client_model/go.MetricFamily` returned a reference-only match for v0.2.0.

## Pinned Version
- Package: `github.com/prometheus/client_model`
- Release: `v0.6.2`
- Import Path: `github.com/prometheus/client_model/go`
- Direct Dependency: `google.golang.org/protobuf v1.36.6`

## Observed Behavior
1. **MetricFamily Initialization and Metadata**:
   - `dto.MetricFamily` encapsulates metric metadata (`Name`, `Help`, `Type`, `Unit`) and a repeated slice of `*dto.Metric` samples.
   - `Unit` is supported on `MetricFamily` and accessible via `GetUnit()`.
2. **Safe Getters and Nil Handling**:
   - `GetName()`, `GetHelp()`, `GetType()`, `GetUnit()`, and `GetMetric()` return valid default zero values when called on a nil receiver `(*dto.MetricFamily)(nil)` or unpopulated struct.
3. **Protobuf Round-Trip Serialization**:
   - `MetricFamily` implements `google.golang.org/protobuf/proto.Message` and round-trips losslessly using `proto.Marshal` and `proto.Unmarshal`.
4. **ProtoReflect Inspection**:
   - `ProtoReflect()` returns a valid `protoreflect.Message` with descriptor full name `io.prometheus.client.MetricFamily`.

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/prometheus/client_model/go.MetricFamily in pkg:golang/github.com/prometheus/client_model@v0.6.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_model@v0.6.2
Demonstrate these symbols/APIs:
  - github.com/prometheus/client_model/go.MetricFamily

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:428526353b0b828c1dd9bfd55d6422700f11d5b85827a3b6eda59320d56e828c","contract":["MetricFamily initializes and organizes Prometheus metric data including Name, Help, Unit, MetricType, and Metric collections.","MetricFamily getter methods GetName, GetHelp, GetType, GetUnit, and GetMetric safely access protobuf fields with default zero-value fallbacks when receiver or fields are nil.","MetricFamily structures containing Counter, Gauge, and Histogram metrics with LabelPairs round-trip losslessly through google.golang.org/protobuf serialization and deserialization.","MetricFamily implements google.golang.org/protobuf protoreflect.Message interface with io.prometheus.client.MetricFamily descriptor full name."],"goal":"verify github.com/prometheus/client_model/go.MetricFamily in pkg:golang/github.com/prometheus/client_model@v0.6.2","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_model@v0.6.2"],"schemaVersion":1,"symbols":["github.com/prometheus/client_model/go.MetricFamily"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","runtime":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/client_model@v0.6.2"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_model@v0.6.2","symbols":["github.com/prometheus/client_model/go.MetricFamily"],"verifierAdapter":"golang@1"}

module example.com/metricfamilysample

go 1.22.0

require (
	github.com/prometheus/client_model v0.6.2
	google.golang.org/protobuf v1.36.6
)

github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
google.golang.org/protobuf v1.36.6 h1:z1NpPI8ku2WgiWnf+t9wTPsn6eP1L7ksHUlkfLvd9xY=
google.golang.org/protobuf v1.36.6/go.mod h1:jduwjTPXsFjZGTmRluh+L6NjiWu7pchiJ2/5YcXBHnY=

package metricfamilysample

import (
	"sort"

	dto "github.com/prometheus/client_model/go"
	"google.golang.org/protobuf/proto"
)

// BuildCounterMetricFamily constructs a MetricFamily with COUNTER type, documentation, unit, and a Metric sample.
func BuildCounterMetricFamily(name, help, unit string, labels map[string]string, value float64) *dto.MetricFamily {
	labelPairs := buildSortedLabelPairs(labels)

	metric := &dto.Metric{
		Label: labelPairs,
		Counter: &dto.Counter{
			Value: proto.Float64(value),
		},
	}

	mf := &dto.MetricFamily{
		Name:   proto.String(name),
		Help:   proto.String(help),
		Type:   dto.MetricType_COUNTER.Enum(),
		Metric: []*dto.Metric{metric},
	}
	if unit != "" {
		mf.Unit = proto.String(unit)
	}

	return mf
}

// BuildGaugeMetricFamily constructs a MetricFamily with GAUGE type, documentation, unit, and a Metric sample.
func BuildGaugeMetricFamily(name, help, unit string, labels map[string]string, value float64) *dto.MetricFamily {
	labelPairs := buildSortedLabelPairs(labels)

	metric := &dto.Metric{
		Label: labelPairs,
		Gauge: &dto.Gauge{
			Value: proto.Float64(value),
		},
	}

	mf := &dto.MetricFamily{
		Name:   proto.String(name),
		Help:   proto.String(help),
		Type:   dto.MetricType_GAUGE.Enum(),
		Metric: []*dto.Metric{metric},
	}
	if unit != "" {
		mf.Unit = proto.String(unit)
	}

	return mf
}

// BuildHistogramMetricFamily constructs a MetricFamily with HISTOGRAM type, documentation, unit, and bucket samples.
func BuildHistogramMetricFamily(name, help, unit string, labels map[string]string, count uint64, sum float64, buckets map[float64]uint64) *dto.MetricFamily {
	labelPairs := buildSortedLabelPairs(labels)

	upperBounds := make([]float64, 0, len(buckets))
	for bound := range buckets {
		upperBounds = append(upperBounds, bound)
	}
	sort.Float64s(upperBounds)

	pbBuckets := make([]*dto.Bucket, 0, len(upperBounds))
	for _, ub := range upperBounds {
		pbBuckets = append(pbBuckets, &dto.Bucket{
			UpperBound:      proto.Float64(ub),
			CumulativeCount: proto.Uint64(buckets[ub]),
		})
	}

	metric := &dto.Metric{
		Label: labelPairs,
		Histogram: &dto.Histogram{
			SampleCount: proto.Uint64(count),
			SampleSum:   proto.Float64(sum),
			Bucket:      pbBuckets,
		},
	}

	mf := &dto.MetricFamily{
		Name:   proto.String(name),
		Help:   proto.String(help),
		Type:   dto.MetricType_HISTOGRAM.Enum(),
		Metric: []*dto.Metric{metric},
	}
	if unit != "" {
		mf.Unit = proto.String(unit)
	}

	return mf
}

// RoundTripMetricFamily serializes and deserializes a MetricFamily using google.golang.org/protobuf/proto.
func RoundTripMetricFamily(mf *dto.MetricFamily) (*dto.MetricFamily, error) {
	data, err := proto.Marshal(mf)
	if err != nil {
		return nil, err
	}
	out := &dto.MetricFamily{}
	if err := proto.Unmarshal(data, out); err != nil {
		return nil, err
	}
	return out, nil
}

func buildSortedLabelPairs(labels map[string]string) []*dto.LabelPair {
	if len(labels) == 0 {
		return nil
	}
	keys := make([]string, 0, len(labels))
	for k := range labels {
		keys = append(keys, k)
	}
	sort.Strings(keys)

	pairs := make([]*dto.LabelPair, 0, len(keys))
	for _, k := range keys {
		pairs = append(pairs, &dto.LabelPair{
			Name:  proto.String(k),
			Value: proto.String(labels[k]),
		})
	}
	return pairs
}

package metricfamilysample_test

import (
	"testing"

	dto "github.com/prometheus/client_model/go"
	"google.golang.org/protobuf/proto"

	"example.com/metricfamilysample"
)

func TestMetricFamilyGettersAndNilSafety(t *testing.T) {
	var nilMF *dto.MetricFamily

	// Assert safe nil receiver access returns zero values
	if nilMF.GetName() != "" {
		t.Errorf("expected empty string for nil GetName, got %q", nilMF.GetName())
	}
	if nilMF.GetHelp() != "" {
		t.Errorf("expected empty string for nil GetHelp, got %q", nilMF.GetHelp())
	}
	if nilMF.GetType() != dto.MetricType_COUNTER {
		t.Errorf("expected default MetricType_COUNTER for nil GetType, got %v", nilMF.GetType())
	}
	if nilMF.GetUnit() != "" {
		t.Errorf("expected empty string for nil GetUnit, got %q", nilMF.GetUnit())
	}
	if nilMF.GetMetric() != nil {
		t.Errorf("expected nil slice for nil GetMetric, got %v", nilMF.GetMetric())
	}

	// Assert unpopulated struct returns zero values
	emptyMF := &dto.MetricFamily{}
	if emptyMF.GetName() != "" {
		t.Errorf("expected empty string for empty GetName, got %q", emptyMF.GetName())
	}
	if emptyMF.GetHelp() != "" {
		t.Errorf("expected empty string for empty GetHelp, got %q", emptyMF.GetHelp())
	}
	if emptyMF.GetType() != dto.MetricType_COUNTER {
		t.Errorf("expected default MetricType_COUNTER for empty GetType, got %v", emptyMF.GetType())
	}
	if emptyMF.GetUnit() != "" {
		t.Errorf("expected empty string for empty GetUnit, got %q", emptyMF.GetUnit())
	}
	if emptyMF.GetMetric() != nil {
		t.Errorf("expected nil slice for empty GetMetric, got %v", emptyMF.GetMetric())
	}

	// Assert populated struct getters return assigned values
	name := "http_requests_total"
	help := "Total number of HTTP requests processed"
	unit := "requests"
	mf := &dto.MetricFamily{
		Name: proto.String(name),
		Help: proto.String(help),
		Type: dto.MetricType_COUNTER.Enum(),
		Unit: proto.String(unit),
	}

	if mf.GetName() != name {
		t.Errorf("expected GetName() = %q, got %q", name, mf.GetName())
	}
	if mf.GetHelp() != help {
		t.Errorf("expected GetHelp() = %q, got %q", help, mf.GetHelp())
	}
	if mf.GetType() != dto.MetricType_COUNTER {
		t.Errorf("expected GetType() = %v, got %v", dto.MetricType_COUNTER, mf.GetType())
	}
	if mf.GetUnit() != unit {
		t.Errorf("expected GetUnit() = %q, got %q", unit, mf.GetUnit())
	}
}

func TestBuildCounterMetricFamily(t *testing.T) {
	labels := map[string]string{
		"method": "GET",
		"status": "200",
	}
	mf := metricfamilysample.BuildCounterMetricFamily(
		"http_requests_total",
		"Total number of HTTP requests processed",
		"requests",
		labels,
		1024.0,
	)

	if mf.GetName() != "http_requests_total" {
		t.Fatalf("expected name http_requests_total, got %s", mf.GetName())
	}
	if mf.GetHelp() != "Total number of HTTP requests processed" {
		t.Fatalf("expected help match, got %s", mf.GetHelp())
	}
	if mf.GetUnit() != "requests" {
		t.Fatalf("expected unit requests, got %s", mf.GetUnit())
	}
	if mf.GetType() != dto.MetricType_COUNTER {
		t.Fatalf("expected type COUNTER, got %v", mf.GetType())
	}
	if len(mf.GetMetric()) != 1 {
		t.Fatalf("expected 1 metric, got %d", len(mf.GetMetric()))
	}

	m := mf.GetMetric()[0]
	if m.GetCounter() == nil {
		t.Fatalf("expected counter to be present")
	}
	if m.GetCounter().GetValue() != 1024.0 {
		t.Fatalf("expected counter value 1024.0, got %f", m.GetCounter().GetValue())
	}
	if len(m.GetLabel()) != 2 {
		t.Fatalf("expected 2 labels, got %d", len(m.GetLabel()))
	}
	if m.GetLabel()[0].GetName() != "method" || m.GetLabel()[0].GetValue() != "GET" {
		t.Errorf("unexpected first label: %v", m.GetLabel()[0])
	}
	if m.GetLabel()[1].GetName() != "status" || m.GetLabel()[1].GetValue() != "200" {
		t.Errorf("unexpected second label: %v", m.GetLabel()[1])
	}
}

func TestBuildGaugeMetricFamily(t *testing.T) {
	labels := map[string]string{
		"instance": "localhost:9090",
	}
	mf := metricfamilysample.BuildGaugeMetricFamily(
		"memory_usage_bytes",
		"Current memory usage in bytes",
		"bytes",
		labels,
		67108864.0,
	)

	if mf.GetName() != "memory_usage_bytes" {
		t.Fatalf("expected name memory_usage_bytes, got %s", mf.GetName())
	}
	if mf.GetUnit() != "bytes" {
		t.Fatalf("expected unit bytes, got %s", mf.GetUnit())
	}
	if mf.GetType() != dto.MetricType_GAUGE {
		t.Fatalf("expected type GAUGE, got %v", mf.GetType())
	}
	if len(mf.GetMetric()) != 1 {
		t.Fatalf("expected 1 metric, got %d", len(mf.GetMetric()))
	}

	m := mf.GetMetric()[0]
	if m.GetGauge() == nil {
		t.Fatalf("expected gauge to be present")
	}
	if m.GetGauge().GetValue() != 67108864.0 {
		t.Fatalf("expected gauge value 67108864.0, got %f", m.GetGauge().GetValue())
	}
}

func TestBuildHistogramMetricFamily(t *testing.T) {
	labels := map[string]string{
		"handler": "api_v1",
	}
	buckets := map[float64]uint64{
		0.05: 10,
		0.1:  25,
		0.5:  50,
		1.0:  60,
	}

	mf := metricfamilysample.BuildHistogramMetricFamily(
		"http_request_duration_seconds",
		"HTTP request duration in seconds",
		"seconds",
		labels,
		60,
		12.5,
		buckets,
	)

	if mf.GetName() != "http_request_duration_seconds" {
		t.Fatalf("expected name http_request_duration_seconds, got %s", mf.GetName())
	}
	if mf.GetUnit() != "seconds" {
		t.Fatalf("expected unit seconds, got %s", mf.GetUnit())
	}
	if mf.GetType() != dto.MetricType_HISTOGRAM {
		t.Fatalf("expected type HISTOGRAM, got %v", mf.GetType())
	}
	if len(mf.GetMetric()) != 1 {
		t.Fatalf("expected 1 metric, got %d", len(mf.GetMetric()))
	}

	h := mf.GetMetric()[0].GetHistogram()
	if h == nil {
		t.Fatalf("expected histogram to be present")
	}
	if h.GetSampleCount() != 60 {
		t.Fatalf("expected sample count 60, got %d", h.GetSampleCount())
	}
	if h.GetSampleSum() != 12.5 {
		t.Fatalf("expected sample sum 12.5, got %f", h.GetSampleSum())
	}
	if len(h.GetBucket()) != 4 {
		t.Fatalf("expected 4 buckets, got %d", len(h.GetBucket()))
	}
	if h.GetBucket()[0].GetUpperBound() != 0.05 || h.GetBucket()[0].GetCumulativeCount() != 10 {
		t.Errorf("unexpected bucket 0: %v", h.GetBucket()[0])
	}
}

func TestMetricFamilyProtobufRoundTripAndEqual(t *testing.T) {
	original := metricfamilysample.BuildHistogramMetricFamily(
		"rpc_latency_seconds",
		"RPC call latency",
		"seconds",
		map[string]string{"service": "catalog"},
		100,
		35.2,
		map[float64]uint64{0.1: 50, 0.5: 90, 1.0: 100},
	)

	deserialized, err := metricfamilysample.RoundTripMetricFamily(original)
	if err != nil {
		t.Fatalf("RoundTripMetricFamily failed: %v", err)
	}

	if !proto.Equal(original, deserialized) {
		t.Fatalf("deserialized MetricFamily is not proto.Equal to original")
	}

	if deserialized.GetName() != original.GetName() {
		t.Errorf("name mismatch: %q != %q", deserialized.GetName(), original.GetName())
	}
	if deserialized.GetUnit() != original.GetUnit() {
		t.Errorf("unit mismatch: %q != %q", deserialized.GetUnit(), original.GetUnit())
	}
	if deserialized.GetHelp() != original.GetHelp() {
		t.Errorf("help mismatch: %q != %q", deserialized.GetHelp(), original.GetHelp())
	}
	if deserialized.GetType() != original.GetType() {
		t.Errorf("type mismatch: %v != %v", deserialized.GetType(), original.GetType())
	}
}

func TestMetricFamilyProtoReflectDescriptor(t *testing.T) {
	mf := &dto.MetricFamily{}
	msg := mf.ProtoReflect()
	if msg == nil {
		t.Fatalf("expected non-nil protoreflect.Message")
	}

	desc := msg.Descriptor()
	if string(desc.FullName()) != "io.prometheus.client.MetricFamily" {
		t.Fatalf("expected descriptor full name io.prometheus.client.MetricFamily, got %s", desc.FullName())
	}

	fields := desc.Fields()
	if fields.ByName("name") == nil {
		t.Errorf("expected 'name' field in descriptor")
	}
	if fields.ByName("unit") == nil {
		t.Errorf("expected 'unit' field in descriptor")
	}
	if fields.ByName("help") == nil {
		t.Errorf("expected 'help' field in descriptor")
	}
	if fields.ByName("type") == nil {
		t.Errorf("expected 'type' field in descriptor")
	}
	if fields.ByName("metric") == nil {
		t.Errorf("expected 'metric' field in descriptor")
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_model/go.MetricFamily in pkg:golang/github.com/prometheus/client_model@v0.6.2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_model@v0.6.2"
  ],
  "symbols": [
    "github.com/prometheus/client_model/go.MetricFamily"
  ]
}