go.opentelemetry.io/otel/trace v1.37.0: TraceFlags

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 go.opentelemetry.io/otel/trace.TraceFlags in pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0
Demonstrate these symbols/APIs:
  - go.opentelemetry.io/otel/trace.TraceFlags

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:b191afda895fedd22ada90ae9c7f1ad565fdafd13cc1cc42182b22bdb7f3f2c9","contract":["TraceFlags represents 8-bit trace options and FlagsSampled is bitmask 0x01.","TraceFlags.IsSampled reports true if and only if FlagsSampled bit is set.","TraceFlags.WithSampled sets or clears FlagsSampled while preserving other bits.","TraceFlags.String formats the byte as a two-character lowercase hex string.","TraceFlags.MarshalJSON serializes the hex string representation to JSON.","SpanContext preserves and returns configured TraceFlags via TraceFlags method."],"goal":"verify go.opentelemetry.io/otel/trace.TraceFlags in pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0","kind":"HOW","packages":["pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0"],"schemaVersion":1,"symbols":["go.opentelemetry.io/otel/trace.TraceFlags"]},"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/trace@v1.37.0"],"schemaVersion":1,"subject":"pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0","symbols":["go.opentelemetry.io/otel/trace.TraceFlags"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require go.opentelemetry.io/otel/trace v1.37.0

require go.opentelemetry.io/otel v1.37.0 // indirect

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/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 v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
go.opentelemetry.io/otel v1.37.0 h1:9zhNfelUvx0KBfu/gb+ZgeAfAgtWrfHJZcAqFC228wQ=
go.opentelemetry.io/otel v1.37.0/go.mod h1:ehE/umFRLnuLa/vSccNq9oS1ErUlkkK71gMcN34UG8I=
go.opentelemetry.io/otel/trace v1.37.0 h1:HLdcFNbRQBE2imdSEgm/kwqmQj1Or1l/7bW6mxVK7z4=
go.opentelemetry.io/otel/trace v1.37.0/go.mod h1:TlgrlQ+PtQO5XFerSPUYG0JSgGyryXewPGyayAWSBS0=
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 (
	"encoding/json"
	"fmt"

	"go.opentelemetry.io/otel/trace"
)

func main() {
	var defaultFlags trace.TraceFlags
	fmt.Printf("Default TraceFlags: %s (sampled: %t)\n", defaultFlags.String(), defaultFlags.IsSampled())

	sampledFlags := trace.FlagsSampled
	fmt.Printf("Sampled TraceFlags: %s (sampled: %t)\n", sampledFlags.String(), sampledFlags.IsSampled())

	toggled := defaultFlags.WithSampled(true)
	fmt.Printf("Default with sampled=true: %s (sampled: %t)\n", toggled.String(), toggled.IsSampled())

	cleared := sampledFlags.WithSampled(false)
	fmt.Printf("Sampled with sampled=false: %s (sampled: %t)\n", cleared.String(), cleared.IsSampled())

	data, err := json.Marshal(sampledFlags)
	if err == nil {
		fmt.Printf("JSON: %s\n", string(data))
	}

	sc := trace.NewSpanContext(trace.SpanContextConfig{
		TraceFlags: trace.FlagsSampled,
	})
	fmt.Printf("SpanContext TraceFlags: %s (sampled: %t)\n", sc.TraceFlags().String(), sc.TraceFlags().IsSampled())
}

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/otel/trace.TraceFlags in pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0"
  ],
  "symbols": [
    "go.opentelemetry.io/otel/trace.TraceFlags"
  ]
}

package main

import (
	"encoding/json"
	"fmt"
	"os"

	"go.opentelemetry.io/otel/trace"
)

func main() {
	// Assertion 1: TraceFlags represents 8-bit trace options and FlagsSampled is bitmask 0x01.
	if byte(trace.FlagsSampled) != 0x01 {
		fmt.Fprintf(os.Stderr, "FAIL: expected FlagsSampled to be 0x01, got 0x%02x\n", byte(trace.FlagsSampled))
		os.Exit(1)
	}

	// Assertion 2: TraceFlags.IsSampled reports true if and only if FlagsSampled bit is set.
	zeroFlags := trace.TraceFlags(0x00)
	if zeroFlags.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected zeroFlags.IsSampled() to be false\n")
		os.Exit(1)
	}
	if !trace.FlagsSampled.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected FlagsSampled.IsSampled() to be true\n")
		os.Exit(1)
	}
	customSampled := trace.TraceFlags(0x05)
	if !customSampled.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected customSampled (0x05).IsSampled() to be true\n")
		os.Exit(1)
	}
	customNonSampled := trace.TraceFlags(0x04)
	if customNonSampled.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected customNonSampled (0x04).IsSampled() to be false\n")
		os.Exit(1)
	}

	// Assertion 3: TraceFlags.WithSampled sets or clears FlagsSampled while preserving other bits.
	withSampledTrue := zeroFlags.WithSampled(true)
	if withSampledTrue != trace.FlagsSampled || !withSampledTrue.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected WithSampled(true) on zero to equal FlagsSampled\n")
		os.Exit(1)
	}
	withSampledFalse := trace.FlagsSampled.WithSampled(false)
	if withSampledFalse != 0x00 || withSampledFalse.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected WithSampled(false) on FlagsSampled to equal 0x00\n")
		os.Exit(1)
	}
	flagsWithOtherBits := trace.TraceFlags(0x06)
	setOther := flagsWithOtherBits.WithSampled(true)
	if setOther != trace.TraceFlags(0x07) || !setOther.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected WithSampled(true) to preserve other bits, got 0x%02x\n", byte(setOther))
		os.Exit(1)
	}
	clearedOther := setOther.WithSampled(false)
	if clearedOther != trace.TraceFlags(0x06) || clearedOther.IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected WithSampled(false) to preserve other bits, got 0x%02x\n", byte(clearedOther))
		os.Exit(1)
	}

	// Assertion 4: TraceFlags.String formats the byte as a two-character lowercase hex string.
	if s := zeroFlags.String(); s != "00" {
		fmt.Fprintf(os.Stderr, "FAIL: expected '00', got '%s'\n", s)
		os.Exit(1)
	}
	if s := trace.FlagsSampled.String(); s != "01" {
		fmt.Fprintf(os.Stderr, "FAIL: expected '01', got '%s'\n", s)
		os.Exit(1)
	}
	if s := trace.TraceFlags(0x0f).String(); s != "0f" {
		fmt.Fprintf(os.Stderr, "FAIL: expected '0f', got '%s'\n", s)
		os.Exit(1)
	}
	if s := trace.TraceFlags(0xff).String(); s != "ff" {
		fmt.Fprintf(os.Stderr, "FAIL: expected 'ff', got '%s'\n", s)
		os.Exit(1)
	}

	// Assertion 5: TraceFlags.MarshalJSON serializes the hex string representation to JSON.
	data, err := json.Marshal(trace.FlagsSampled)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unexpected json.Marshal error: %v\n", err)
		os.Exit(1)
	}
	if string(data) != `"01"` {
		fmt.Fprintf(os.Stderr, "FAIL: expected '\"01\"', got '%s'\n", string(data))
		os.Exit(1)
	}
	dataZero, err := json.Marshal(zeroFlags)
	if err != nil || string(dataZero) != `"00"` {
		fmt.Fprintf(os.Stderr, "FAIL: expected '\"00\"', got '%s'\n", string(dataZero))
		os.Exit(1)
	}

	// Assertion 6: SpanContext preserves and returns configured TraceFlags via TraceFlags method.
	sc := trace.NewSpanContext(trace.SpanContextConfig{
		TraceFlags: trace.FlagsSampled,
	})
	if sc.TraceFlags() != trace.FlagsSampled || !sc.TraceFlags().IsSampled() {
		fmt.Fprintf(os.Stderr, "FAIL: expected SpanContext to preserve FlagsSampled\n")
		os.Exit(1)
	}

	fmt.Println("PASS: all TraceFlags contract assertions passed.")
}