github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4: go.Gauge

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.Gauge 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.Gauge

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:sha256:62bea9decbf991cc6daa1cbedc5472cd01f537513a38d01be8adfd74ca101182","contract":["dto.Gauge.GetValue returns 0 for a nil or uninitialized Gauge, and returns the configured float64 value when set","dto.Gauge.Reset resets the gauge value back to 0 and clears the Value pointer","dto.Gauge.Descriptor returns the protobuf descriptor bytes and tag path for Gauge"],"goal":"verify github.com/prometheus/client_model/go.Gauge 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.Gauge"]},"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.Gauge"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

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

require github.com/golang/protobuf v1.2.0 // indirect

github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
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 h1:Bl/8QSvNqXvPGPGXa2z5xUTmV7VDcZyvRZ+QQXkXTZQ=
golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

package main

import (
	"fmt"

	dto "github.com/prometheus/client_model/go"
)

func main() {
	val := 42.5
	gauge := &dto.Gauge{
		Value: &val,
	}

	fmt.Printf("Gauge value: %f\n", gauge.GetValue())
	fmt.Printf("Gauge string: %s\n", gauge.String())

	gauge.Reset()
	fmt.Printf("Gauge value after reset: %f\n", gauge.GetValue())
}

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

package main

import (
	"fmt"
	"os"

	dto "github.com/prometheus/client_model/go"
)

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

	emptyGauge := &dto.Gauge{}
	if got := emptyGauge.GetValue(); got != 0 {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: emptyGauge.GetValue() = %v, want 0\n", got)
		os.Exit(1)
	}

	val := 123.456
	gauge := &dto.Gauge{Value: &val}
	if got := gauge.GetValue(); got != val {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: gauge.GetValue() = %v, want %v\n", got, val)
		os.Exit(1)
	}

	// Assertion 2: dto.Gauge.Reset resets the gauge value back to 0 and clears the Value pointer
	resetGauge := &dto.Gauge{Value: &val}
	resetGauge.Reset()
	if got := resetGauge.GetValue(); got != 0 {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: resetGauge.GetValue() = %v, want 0\n", got)
		os.Exit(1)
	}
	if resetGauge.Value != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: resetGauge.Value = %v, want nil\n", resetGauge.Value)
		os.Exit(1)
	}

	// Assertion 3: dto.Gauge.Descriptor returns the protobuf descriptor bytes and tag path for Gauge
	descBytes, descPath := gauge.Descriptor()
	if len(descBytes) == 0 {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: len(descBytes) = 0\n")
		os.Exit(1)
	}
	if len(descPath) != 1 || descPath[0] != 1 {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: descPath = %v, want [1]\n", descPath)
		os.Exit(1)
	}

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