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

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.Counter 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.Counter
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:ec8fc052d738ca9018b13b6a57adac1776cbeb6a5651cf177c95355d0420241a","contract":["dto.Counter.GetValue returns 0 for a nil or uninitialized Counter, and returns the configured float64 value when set.","dto.Counter attaches an Exemplar containing label pairs, float64 value, and timestamp, accessible via GetExemplar.","dto.Counter.Reset resets the counter value back to 0."],"goal":"verify github.com/prometheus/client_model/go.Counter 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.Counter"]},"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.Counter"],"verifierAdapter":"golang@1"}

module example.com/counter

go 1.26.6

require (
	github.com/golang/protobuf v1.5.3
	github.com/prometheus/client_model v0.2.0
)

require google.golang.org/protobuf v1.26.0 // indirect

github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
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/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
google.golang.org/protobuf v1.26.0 h1:bxAC2xTBsZGibn2RTntX0oH50xLsqy1OxA9tTL3p/lk=
google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=

package main

import (
	"fmt"
	"time"

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

func main() {
	ts, _ := ptypes.TimestampProto(time.Now())
	exemplar := &dto.Exemplar{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String("trace_id"),
				Value: proto.String("abc-123"),
			},
		},
		Value:     proto.Float64(1.0),
		Timestamp: ts,
	}

	counter := &dto.Counter{
		Value:    proto.Float64(42.0),
		Exemplar: exemplar,
	}

	fmt.Printf("Counter value: %f\n", counter.GetValue())
	if ex := counter.GetExemplar(); ex != nil {
		fmt.Printf("Exemplar value: %f\n", ex.GetValue())
	}

	counter.Reset()
	fmt.Printf("After reset: %f\n", counter.GetValue())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_model/go.Counter 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.Counter"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package test

import (
	"testing"
	"time"

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

func TestCounterGetValue(t *testing.T) {
	// Nil counter returns 0
	var nilCounter *dto.Counter
	if got := nilCounter.GetValue(); got != 0 {
		t.Errorf("nilCounter.GetValue() = %v, want 0", got)
	}

	// Empty counter returns 0
	emptyCounter := &dto.Counter{}
	if got := emptyCounter.GetValue(); got != 0 {
		t.Errorf("emptyCounter.GetValue() = %v, want 0", got)
	}

	// Counter with configured value
	val := 42.5
	counter := &dto.Counter{
		Value: proto.Float64(val),
	}
	if got := counter.GetValue(); got != val {
		t.Errorf("counter.GetValue() = %v, want %v", got, val)
	}
}

func TestCounterExemplar(t *testing.T) {
	labelName := "trace_id"
	labelVal := "abc-123"
	exemplarVal := 1.5
	now := time.Now()
	ts, err := ptypes.TimestampProto(now)
	if err != nil {
		t.Fatalf("ptypes.TimestampProto failed: %v", err)
	}

	exemplar := &dto.Exemplar{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String(labelName),
				Value: proto.String(labelVal),
			},
		},
		Value:     proto.Float64(exemplarVal),
		Timestamp: ts,
	}

	counter := &dto.Counter{
		Value:    proto.Float64(100.0),
		Exemplar: exemplar,
	}

	got := counter.GetExemplar()
	if got == nil {
		t.Fatal("counter.GetExemplar() returned nil, expected exemplar")
	}
	if got.GetValue() != exemplarVal {
		t.Errorf("exemplar.GetValue() = %v, want %v", got.GetValue(), exemplarVal)
	}
	if len(got.GetLabel()) != 1 || got.GetLabel()[0].GetName() != labelName || got.GetLabel()[0].GetValue() != labelVal {
		t.Errorf("exemplar labels mismatch: got %v", got.GetLabel())
	}
	if got.GetTimestamp().GetSeconds() != ts.GetSeconds() {
		t.Errorf("exemplar timestamp seconds mismatch: got %v, want %v", got.GetTimestamp().GetSeconds(), ts.GetSeconds())
	}
}

func TestCounterReset(t *testing.T) {
	counter := &dto.Counter{
		Value: proto.Float64(99.9),
	}
	counter.Reset()
	if got := counter.GetValue(); got != 0 {
		t.Errorf("counter.GetValue() after Reset() = %v, want 0", got)
	}
}