github.com/prometheus/client_model v0.2.0: go.LabelPair

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.LabelPair 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.LabelPair

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:sha256:43361246083c451a1d7f6955e9d2c42388532928f8c0363f78db2001d8dec74e","contract":["dto.LabelPair.GetName and dto.LabelPair.GetValue return empty strings on a nil or empty LabelPair, and return configured string values when set.","dto.LabelPair can be instantiated with name and value pointers, serialized and deserialized via proto preserving label fields.","dto.LabelPair.Reset clears all fields of the LabelPair struct.","dto.LabelPair can be used in Prometheus metrics label collections."],"goal":"verify github.com/prometheus/client_model/go.LabelPair 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.LabelPair"]},"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.LabelPair"],"verifierAdapter":"golang@1"}

module example.com/labelpair

go 1.22.0

require (
	github.com/golang/protobuf v1.5.4
	github.com/prometheus/client_model v0.2.0
)

require google.golang.org/protobuf v1.36.6 // indirect

github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
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 v1.36.6 h1:z1NpPI8ku2WgiWnf+t9wTPsn6eP1L7ksHUlkfLvd9xY=
google.golang.org/protobuf v1.36.6/go.mod h1:jduwjTPXsFjZGTmRluh+L6NjiWu7pchiJ2/5YcXBHnY=

package main

import (
	"fmt"

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

func main() {
	lp := &dto.LabelPair{
		Name:  proto.String("service"),
		Value: proto.String("web"),
	}

	fmt.Printf("Label: %s=%s\n", lp.GetName(), lp.GetValue())

	data, err := proto.Marshal(lp)
	if err != nil {
		panic(err)
	}

	decoded := &dto.LabelPair{}
	if err := proto.Unmarshal(data, decoded); err != nil {
		panic(err)
	}

	fmt.Printf("Decoded: %s=%s\n", decoded.GetName(), decoded.GetValue())
	lp.Reset()
	fmt.Printf("After Reset: %s=%s\n", lp.GetName(), lp.GetValue())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_model/go.LabelPair 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.LabelPair"
  ]
}

package test

import (
	"testing"

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

func TestLabelPairGetters(t *testing.T) {
	var nilLP *dto.LabelPair
	if got := nilLP.GetName(); got != "" {
		t.Errorf("nilLP.GetName() = %q, want \"\"", got)
	}
	if got := nilLP.GetValue(); got != "" {
		t.Errorf("nilLP.GetValue() = %q, want \"\"", got)
	}

	emptyLP := &dto.LabelPair{}
	if got := emptyLP.GetName(); got != "" {
		t.Errorf("emptyLP.GetName() = %q, want \"\"", got)
	}
	if got := emptyLP.GetValue(); got != "" {
		t.Errorf("emptyLP.GetValue() = %q, want \"\"", got)
	}

	name := "service_name"
	val := "order_processor"
	lp := &dto.LabelPair{
		Name:  proto.String(name),
		Value: proto.String(val),
	}
	if got := lp.GetName(); got != name {
		t.Errorf("lp.GetName() = %q, want %q", got, name)
	}
	if got := lp.GetValue(); got != val {
		t.Errorf("lp.GetValue() = %q, want %q", got, val)
	}
}

func TestLabelPairProtobufSerialization(t *testing.T) {
	name := "http_method"
	val := "POST"
	original := &dto.LabelPair{
		Name:  proto.String(name),
		Value: proto.String(val),
	}

	data, err := proto.Marshal(original)
	if err != nil {
		t.Fatalf("proto.Marshal failed: %v", err)
	}

	decoded := &dto.LabelPair{}
	if err := proto.Unmarshal(data, decoded); err != nil {
		t.Fatalf("proto.Unmarshal failed: %v", err)
	}

	if decoded.GetName() != name {
		t.Errorf("decoded.GetName() = %q, want %q", decoded.GetName(), name)
	}
	if decoded.GetValue() != val {
		t.Errorf("decoded.GetValue() = %q, want %q", decoded.GetValue(), val)
	}
	if !proto.Equal(original, decoded) {
		t.Error("proto.Equal(original, decoded) = false, want true")
	}
}

func TestLabelPairReset(t *testing.T) {
	lp := &dto.LabelPair{
		Name:  proto.String("region"),
		Value: proto.String("us-west-2"),
	}

	lp.Reset()

	if got := lp.GetName(); got != "" {
		t.Errorf("after Reset(), lp.GetName() = %q, want \"\"", got)
	}
	if got := lp.GetValue(); got != "" {
		t.Errorf("after Reset(), lp.GetValue() = %q, want \"\"", got)
	}
}

func TestLabelPairInMetric(t *testing.T) {
	metric := &dto.Metric{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String("instance"),
				Value: proto.String("web-01"),
			},
			{
				Name:  proto.String("job"),
				Value: proto.String("api"),
			},
		},
		Counter: &dto.Counter{
			Value: proto.Float64(128.0),
		},
	}

	labels := metric.GetLabel()
	if len(labels) != 2 {
		t.Fatalf("len(metric.GetLabel()) = %d, want 2", len(labels))
	}
	if labels[0].GetName() != "instance" || labels[0].GetValue() != "web-01" {
		t.Errorf("label[0] = %s=%s, want instance=web-01", labels[0].GetName(), labels[0].GetValue())
	}
	if labels[1].GetName() != "job" || labels[1].GetValue() != "api" {
		t.Errorf("label[1] = %s=%s, want job=api", labels[1].GetName(), labels[1].GetValue())
	}
}