github.com/prometheus/client_model v0.6.1: 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@v0.6.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_model@v0.6.1
Demonstrate these symbols/APIs:
  - github.com/prometheus/client_model/go.Counter

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:a8c4b562d56a369d731628a2656b84eedd85c602fc8244578c5b319c23503ada","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 attaches a CreatedTimestamp accessible via GetCreatedTimestamp, returning nil when unset.","dto.Counter.Reset resets the counter value and all nested fields back to their zero values."],"goal":"verify github.com/prometheus/client_model/go.Counter in pkg:golang/github.com/prometheus/client_model@v0.6.1","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_model@v0.6.1"],"schemaVersion":1,"symbols":["github.com/prometheus/client_model/go.Counter"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/client_model@v0.6.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_model@v0.6.1","symbols":["github.com/prometheus/client_model/go.Counter"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

require (
	github.com/prometheus/client_model v0.6.1
	google.golang.org/protobuf v1.33.0
)

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 v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
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 v1.33.0 h1:uNO2rsAINq/JlFpSdYEKIZ0uKD/R9cpdv0T+yoGwGmI=
google.golang.org/protobuf v1.33.0/go.mod h1:c6P6GXX6sHbq/GpV6MGZEdwhWPcYBgnhAHhKbcUYpos=

package main

import (
	"fmt"
	"time"

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

func main() {
	now := time.Now()
	ts := timestamppb.New(now)
	exemplar := &dto.Exemplar{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String("trace_id"),
				Value: proto.String("trace-42"),
			},
		},
		Value:     proto.Float64(3.14),
		Timestamp: ts,
	}

	createdTs := timestamppb.New(now.Add(-time.Hour))

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

	fmt.Printf("Counter value: %f\n", counter.GetValue())
	if ex := counter.GetExemplar(); ex != nil {
		fmt.Printf("Exemplar value: %f\n", ex.GetValue())
	}
	if ct := counter.GetCreatedTimestamp(); ct != nil {
		fmt.Printf("Created timestamp: %s\n", ct.AsTime().Format(time.RFC3339))
	}

	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@v0.6.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_model@v0.6.1"
  ],
  "symbols": [
    "github.com/prometheus/client_model/go.Counter"
  ]
}

package main

import (
	"fmt"
	"os"
	"time"

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

func main() {
	// 1. dto.Counter.GetValue returns 0 for a nil or uninitialized Counter, and returns the configured float64 value when set.
	var nilCounter *dto.Counter
	if got := nilCounter.GetValue(); got != 0 {
		fmt.Fprintf(os.Stderr, "nilCounter.GetValue() expected 0, got %v\n", got)
		os.Exit(1)
	}

	emptyCounter := &dto.Counter{}
	if got := emptyCounter.GetValue(); got != 0 {
		fmt.Fprintf(os.Stderr, "emptyCounter.GetValue() expected 0, got %v\n", got)
		os.Exit(1)
	}

	val := 42.5
	counter := &dto.Counter{
		Value: proto.Float64(val),
	}
	if got := counter.GetValue(); got != val {
		fmt.Fprintf(os.Stderr, "counter.GetValue() expected %v, got %v\n", val, got)
		os.Exit(1)
	}

	// 2. dto.Counter attaches an Exemplar containing label pairs, float64 value, and timestamp, accessible via GetExemplar.
	if emptyCounter.GetExemplar() != nil {
		fmt.Fprintf(os.Stderr, "emptyCounter.GetExemplar() expected nil, got %v\n", emptyCounter.GetExemplar())
		os.Exit(1)
	}

	labelName := "trace_id"
	labelVal := "abc-123"
	exemplarVal := 1.5
	now := time.Now()
	ts := timestamppb.New(now)

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

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

	gotEx := counterWithExemplar.GetExemplar()
	if gotEx == nil {
		fmt.Fprintf(os.Stderr, "counter.GetExemplar() expected non-nil exemplar\n")
		os.Exit(1)
	}
	if gotEx.GetValue() != exemplarVal {
		fmt.Fprintf(os.Stderr, "exemplar.GetValue() expected %v, got %v\n", exemplarVal, gotEx.GetValue())
		os.Exit(1)
	}
	if len(gotEx.GetLabel()) != 1 || gotEx.GetLabel()[0].GetName() != labelName || gotEx.GetLabel()[0].GetValue() != labelVal {
		fmt.Fprintf(os.Stderr, "exemplar label mismatch: got %v\n", gotEx.GetLabel())
		os.Exit(1)
	}
	if gotEx.GetTimestamp().GetSeconds() != ts.GetSeconds() {
		fmt.Fprintf(os.Stderr, "exemplar timestamp seconds mismatch: got %v, want %v\n", gotEx.GetTimestamp().GetSeconds(), ts.GetSeconds())
		os.Exit(1)
	}

	// 3. dto.Counter attaches a CreatedTimestamp accessible via GetCreatedTimestamp, returning nil when unset.
	if nilCounter.GetCreatedTimestamp() != nil {
		fmt.Fprintf(os.Stderr, "nilCounter.GetCreatedTimestamp() expected nil\n")
		os.Exit(1)
	}
	if emptyCounter.GetCreatedTimestamp() != nil {
		fmt.Fprintf(os.Stderr, "emptyCounter.GetCreatedTimestamp() expected nil\n")
		os.Exit(1)
	}

	createdTs := timestamppb.New(now.Add(-time.Hour))
	counterWithCreatedTs := &dto.Counter{
		Value:            proto.Float64(50.0),
		CreatedTimestamp: createdTs,
	}
	gotCreated := counterWithCreatedTs.GetCreatedTimestamp()
	if gotCreated == nil {
		fmt.Fprintf(os.Stderr, "counter.GetCreatedTimestamp() expected non-nil timestamp\n")
		os.Exit(1)
	}
	if gotCreated.GetSeconds() != createdTs.GetSeconds() || gotCreated.GetNanos() != createdTs.GetNanos() {
		fmt.Fprintf(os.Stderr, "created timestamp mismatch: got %v, want %v\n", gotCreated, createdTs)
		os.Exit(1)
	}

	// 4. dto.Counter.Reset resets the counter value and all nested fields back to their zero values.
	counterToReset := &dto.Counter{
		Value:            proto.Float64(99.9),
		Exemplar:         exemplar,
		CreatedTimestamp: createdTs,
	}
	counterToReset.Reset()
	if got := counterToReset.GetValue(); got != 0 {
		fmt.Fprintf(os.Stderr, "counter.GetValue() after Reset() expected 0, got %v\n", got)
		os.Exit(1)
	}
	if counterToReset.GetExemplar() != nil {
		fmt.Fprintf(os.Stderr, "counter.GetExemplar() after Reset() expected nil, got %v\n", counterToReset.GetExemplar())
		os.Exit(1)
	}
	if counterToReset.GetCreatedTimestamp() != nil {
		fmt.Fprintf(os.Stderr, "counter.GetCreatedTimestamp() after Reset() expected nil, got %v\n", counterToReset.GetCreatedTimestamp())
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}