github.com/prometheus/client_model v0.2.0: 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@v0.2.0` with `github.com/prometheus/client_model/go.MetricFamily` returned reference-only match for v0.5.0.

## Pinned Version
- Package: `github.com/prometheus/client_model`
- Release: `v0.2.0` (in `go.mod` / `go.sum`)
- Import Path: `github.com/prometheus/client_model/go`

## Observed Behavior
1. **MetricFamily Creation and Structuring**:
   - `dto.MetricFamily` holds metric metadata (`Name`, `Help`, `Type`) and a slice of `*dto.Metric` items.
   - Metrics contain `LabelPair` slices and type-specific metric data such as `*dto.Counter` or `*dto.Gauge`.
2. **Safe Getters and Nil Handling**:
   - `GetName()`, `GetHelp()`, `GetType()`, and `GetMetric()` return valid defaults or empty values when called on nil receivers or unset fields.
3. **Protobuf Compatibility**:
   - In `v0.2.0`, generated protobuf code implements `github.com/golang/protobuf/proto.Message` rather than `google.golang.org/protobuf/proto.Message`.
   - Round-trip serialization/deserialization works losslessly via `github.com/golang/protobuf/proto`.

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@v0.2.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_model@v0.2.0
Demonstrate these symbols/APIs:
  - github.com/prometheus/client_model/go.MetricFamily
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:cbd903df630044d3b95a47ca3855b986994edf1e51db0b9916c20f341efadefc","contract":["MetricFamily initializes and organizes Prometheus metric data including Name, Help, MetricType, and Metric collections.","MetricFamily getter methods GetName, GetHelp, GetType, and GetMetric safely access protobuf fields with default zero-value fallbacks when receiver or fields are nil.","MetricFamily structures containing Counter and Gauge metrics with LabelPairs round-trip losslessly through protobuf serialization and deserialization."],"goal":"verify github.com/prometheus/client_model/go.MetricFamily in pkg:golang/github.com/prometheus/client_model@v0.2.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_model@v0.2.0"],"schemaVersion":1,"symbols":["github.com/prometheus/client_model/go.MetricFamily"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","executionContext":"go","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@v0.2.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_model@v0.2.0","symbols":["github.com/prometheus/client_model/go.MetricFamily"],"verifierAdapter":"golang@1"}

module example.com/clientmodelsample

go 1.22

require (
	github.com/golang/protobuf v1.5.0
	github.com/prometheus/client_model v0.2.0
)

require google.golang.org/protobuf v1.26.0-rc.1 // indirect

github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
github.com/golang/protobuf v1.5.0 h1:LUVKkCeviFUMKqHa4tXIIij/lbhnMbP7Fn5wKdKkRh4=
github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
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 v0.2.0 h1:uq5h0d+GuxiXLJLNABMgp2qUWDPiLvgCzz2dUR+/W/M=
github.com/prometheus/client_model v0.2.0/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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 v1.26.0-rc.1 h1:7QnIQpGRHE5RnLKnESfDoxm2dTapTZua5a0kS0A+VXQ=
google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=

package clientmodelsample

import (
	"github.com/golang/protobuf/proto"
	dto "github.com/prometheus/client_model/go"
)

// BuildCounterMetricFamily constructs a MetricFamily for counter metrics.
func BuildCounterMetricFamily(name, help string, labels map[string]string, value float64) *dto.MetricFamily {
	labelPairs := make([]*dto.LabelPair, 0, len(labels))
	for k, v := range labels {
		labelPairs = append(labelPairs, &dto.LabelPair{
			Name:  proto.String(k),
			Value: proto.String(v),
		})
	}

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

	return &dto.MetricFamily{
		Name:   proto.String(name),
		Help:   proto.String(help),
		Type:   dto.MetricType_COUNTER.Enum(),
		Metric: []*dto.Metric{metric},
	}
}

// BuildGaugeMetricFamily constructs a MetricFamily for gauge metrics.
func BuildGaugeMetricFamily(name, help string, labels map[string]string, value float64) *dto.MetricFamily {
	labelPairs := make([]*dto.LabelPair, 0, len(labels))
	for k, v := range labels {
		labelPairs = append(labelPairs, &dto.LabelPair{
			Name:  proto.String(k),
			Value: proto.String(v),
		})
	}

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

	return &dto.MetricFamily{
		Name:   proto.String(name),
		Help:   proto.String(help),
		Type:   dto.MetricType_GAUGE.Enum(),
		Metric: []*dto.Metric{metric},
	}
}

// RoundTripMetricFamily marshals and unmarshals a MetricFamily using protobuf.
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
}

package clientmodelsample_test

import (
	"testing"

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

	"example.com/clientmodelsample"
)

func TestMetricFamilyGettersAndDefaults(t *testing.T) {
	var nilMF *dto.MetricFamily
	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.GetMetric() != nil {
		t.Errorf("expected nil slice for nil GetMetric, got %v", nilMF.GetMetric())
	}

	name := "http_requests_total"
	help := "Total number of HTTP requests processed"
	mf := &dto.MetricFamily{
		Name: proto.String(name),
		Help: proto.String(help),
		Type: dto.MetricType_COUNTER.Enum(),
	}

	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())
	}
}

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

	if mf.GetName() != "http_requests_total" {
		t.Fatalf("expected name http_requests_total, got %s", mf.GetName())
	}
	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()))
	}
}

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

	if mf.GetName() != "memory_usage_bytes" {
		t.Fatalf("expected name memory_usage_bytes, got %s", mf.GetName())
	}
	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 TestMetricFamilyRoundTripProtobuf(t *testing.T) {
	original := clientmodelsample.BuildCounterMetricFamily(
		"rpc_duration_seconds_count",
		"RPC duration count",
		map[string]string{"service": "auth"},
		42.0,
	)

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

	if deserialized.GetName() != original.GetName() {
		t.Errorf("deserialized name mismatch: expected %q, got %q", original.GetName(), deserialized.GetName())
	}
	if deserialized.GetHelp() != original.GetHelp() {
		t.Errorf("deserialized help mismatch: expected %q, got %q", original.GetHelp(), deserialized.GetHelp())
	}
	if deserialized.GetType() != original.GetType() {
		t.Errorf("deserialized type mismatch: expected %v, got %v", original.GetType(), deserialized.GetType())
	}
	if len(deserialized.GetMetric()) != len(original.GetMetric()) {
		t.Fatalf("metric length mismatch: expected %d, got %d", len(original.GetMetric()), len(deserialized.GetMetric()))
	}

	origMetric := original.GetMetric()[0]
	deserMetric := deserialized.GetMetric()[0]
	if deserMetric.GetCounter().GetValue() != origMetric.GetCounter().GetValue() {
		t.Errorf("metric counter value mismatch: expected %f, got %f",
			origMetric.GetCounter().GetValue(), deserMetric.GetCounter().GetValue())
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_model/go.MetricFamily in pkg:golang/github.com/prometheus/client_model@v0.2.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_model@v0.2.0"
  ],
  "symbols": [
    "github.com/prometheus/client_model/go.MetricFamily"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}