go.opentelemetry.io/otel/metric/x v0.66.0

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 pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0

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:sha256:9c07ab7d6c4f481d0aec34d7100bd3c8cfe144bdd97aa524724b0bf6e07da328","contract":["WithDefaultAttributes creates an InstrumentOption with allowed attribute keys","Instruments created with WithDefaultAttributes record measurements successfully","Settable interface allows mutation of reusable options"],"goal":"verify pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0"],"schemaVersion":1},"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/go.opentelemetry.io/otel/metric/x@v0.66.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0","verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require (
	go.opentelemetry.io/otel v1.44.0
	go.opentelemetry.io/otel/metric v1.44.0
	go.opentelemetry.io/otel/metric/x v0.66.0
)

require github.com/cespare/xxhash/v2 v2.3.0 // indirect

github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
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/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
go.opentelemetry.io/otel v1.44.0 h1:JjwHmHpA4iZ3wBxluu2fbbE7j4kqlE8jXyAyPXH7HqU=
go.opentelemetry.io/otel v1.44.0/go.mod h1:BMgjTHL9WPRlRjL2oZCBTL4whCGtXch2H4BhOPIAyYc=
go.opentelemetry.io/otel/metric v1.44.0 h1:1w0gILTcHdr3YI+ixLyjemwrVnsMURbTZFrSYCdDdmc=
go.opentelemetry.io/otel/metric v1.44.0/go.mod h1:8O7hanEPBNgEMmybD3s2VBKcgWOCsA6tzHBPODAiquo=
go.opentelemetry.io/otel/metric/x v0.66.0 h1:YkCrx1zLOChi9ZcZ6euupOcsgzbVlec7D/xoEU1+cTA=
go.opentelemetry.io/otel/metric/x v0.66.0/go.mod h1:d1+BDj9t96do0/1LoU1ayfCv79ZgNE41qbhBvnMOBZk=
go.opentelemetry.io/otel/trace v1.44.0 h1:jxF5CsGYCe74MCRx2X4g7WsY/VBKRqqpNvXlX/6gtIk=
go.opentelemetry.io/otel/trace v1.44.0/go.mod h1:oLl1jrMQAVo6v3GAggN+1VH9VIz9iUSvW53sW1Q8PIE=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"context"
	"fmt"
	"log"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/metric/noop"
	"go.opentelemetry.io/otel/metric/x"
)

// reusableOption implements x.Settable to allow reusing measurement options.
type reusableOption struct {
	metric.MeasurementOption
	attrs []attribute.KeyValue
}

func (r *reusableOption) Set(attrs []attribute.KeyValue) {
	r.attrs = attrs
}

func main() {
	ctx := context.Background()

	// Configure instrument with default attribute keys
	defaultOpt := x.WithDefaultAttributes(
		attribute.Key("service.name"),
		attribute.Key("environment"),
	)

	// Create a counter instrument using the experimental option
	meter := noop.NewMeterProvider().Meter("example.com/sample")
	counter, err := meter.Int64Counter("sample_requests_total", defaultOpt)
	if err != nil {
		log.Fatalf("failed to create counter: %v", err)
	}

	// Use reusable option via Settable interface
	opt := &reusableOption{
		attrs: []attribute.KeyValue{
			attribute.String("service.name", "billing"),
			attribute.String("environment", "staging"),
		},
	}
	counter.Add(ctx, 1)

	var settable x.Settable[[]attribute.KeyValue] = opt
	settable.Set([]attribute.KeyValue{
		attribute.String("service.name", "billing"),
		attribute.String("environment", "production"),
	})
	counter.Add(ctx, 2)

	fmt.Println("Metric observations recorded successfully")
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/otel/metric/x@v0.66.0"
  ]
}

package main

import (
	"context"
	"fmt"
	"os"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/metric/noop"
	"go.opentelemetry.io/otel/metric/x"
)

type reusableOption struct {
	metric.MeasurementOption
	attrs []attribute.KeyValue
}

func (r *reusableOption) Set(attrs []attribute.KeyValue) {
	r.attrs = attrs
}

func main() {
	ctx := context.Background()

	// 1. WithDefaultAttributes creates an InstrumentOption with allowed attribute keys
	defaultOpt := x.WithDefaultAttributes(
		attribute.Key("service.name"),
		attribute.Key("environment"),
	)
	if defaultOpt == nil {
		fmt.Fprintln(os.Stderr, "WithDefaultAttributes returned nil")
		os.Exit(1)
	}
	allowed, ok := defaultOpt.(interface{ AllowedKeys() []attribute.Key })
	if !ok {
		fmt.Fprintln(os.Stderr, "defaultOpt does not implement AllowedKeys()")
		os.Exit(1)
	}
	keys := allowed.AllowedKeys()
	if len(keys) != 2 || keys[0] != "service.name" || keys[1] != "environment" {
		fmt.Fprintf(os.Stderr, "unexpected AllowedKeys: %v\n", keys)
		os.Exit(1)
	}

	// 2. Instruments created with WithDefaultAttributes record measurements successfully
	mp := noop.NewMeterProvider()
	meter := mp.Meter("example.com/sample")
	counter, err := meter.Int64Counter("sample_requests_total", defaultOpt)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create counter: %v\n", err)
		os.Exit(1)
	}
	counter.Add(ctx, 1, metric.WithAttributes(
		attribute.String("service.name", "demo"),
		attribute.String("environment", "staging"),
	))

	// 3. Settable interface allows mutation of reusable options
	opt := &reusableOption{
		attrs: []attribute.KeyValue{
			attribute.String("environment", "staging"),
		},
	}
	var settable x.Settable[[]attribute.KeyValue] = opt
	settable.Set([]attribute.KeyValue{
		attribute.String("environment", "production"),
	})
	if len(opt.attrs) != 1 || opt.attrs[0].Key != "environment" || opt.attrs[0].Value.AsString() != "production" {
		fmt.Fprintf(os.Stderr, "unexpected attributes after Set: %v\n", opt.attrs)
		os.Exit(1)
	}

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