github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4: 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@v0.0.0-20190812154241-14fe0d1b01d4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_model@v0.0.0-20190812154241-14fe0d1b01d4
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:sha256:802a57120ca49bb573092edea2c9aab9ef5ab9a9a1318c303ec7b49afa6f63c3","contract":["dto.Counter.GetValue returns 0 for a nil or uninitialized Counter, and returns the configured float64 value when set.","dto.Counter.Reset resets the counter value back to zero.","dto.Counter serializes to and deserializes from protocol buffer wire format via proto.Marshal and proto.Unmarshal."],"goal":"verify github.com/prometheus/client_model/go.Counter in pkg:golang/github.com/prometheus/client_model@v0.0.0-20190812154241-14fe0d1b01d4","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_model@v0.0.0-20190812154241-14fe0d1b01d4"],"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@v0.0.0-20190812154241-14fe0d1b01d4"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_model@v0.0.0-20190812154241-14fe0d1b01d4","symbols":["github.com/prometheus/client_model/go.Counter"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.23

require github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4

require (
	github.com/golang/protobuf v1.5.0 // indirect
	google.golang.org/protobuf v1.36.12 // 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/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4 h1:gQz4mCbXsO+nc9n1hCxHcGA3Zx3Eo+UHZoInFGUIXNM=
github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/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/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
google.golang.org/protobuf v1.36.12 h1:pJOKDDOyeXErUroCihFAd5LQuwXBSpVnKGrj5o/fwxc=
google.golang.org/protobuf v1.36.12/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=

package main

import (
	"fmt"

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

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

	fmt.Printf("Counter value: %f\n", counter.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@v0.0.0-20190812154241-14fe0d1b01d4",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_model@v0.0.0-20190812154241-14fe0d1b01d4"
  ],
  "symbols": [
    "github.com/prometheus/client_model/go.Counter"
  ]
}

package main

import (
	"fmt"
	"os"

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

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.Reset resets the counter value back to zero.
	counterToReset := &dto.Counter{
		Value: proto.Float64(99.9),
	}
	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)
	}

	// 3. dto.Counter serializes to and deserializes from protocol buffer wire format via proto.Marshal and proto.Unmarshal.
	original := &dto.Counter{
		Value: proto.Float64(123.456),
	}
	data, err := proto.Marshal(original)
	if err != nil {
		fmt.Fprintf(os.Stderr, "proto.Marshal failed: %v\n", err)
		os.Exit(1)
	}

	var decoded dto.Counter
	if err := proto.Unmarshal(data, &decoded); err != nil {
		fmt.Fprintf(os.Stderr, "proto.Unmarshal failed: %v\n", err)
		os.Exit(1)
	}

	if decoded.GetValue() != 123.456 {
		fmt.Fprintf(os.Stderr, "decoded value expected 123.456, got %v\n", decoded.GetValue())
		os.Exit(1)
	}

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