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

# OpenTelemetry Go SpanIDFromHex Contract Validation

## Summary
Validates `go.opentelemetry.io/otel/trace.SpanIDFromHex` behavior for `pkg:golang/go.opentelemetry.io/otel/trace@v1.37.0`.

## Pinned Release
- `go.opentelemetry.io/otel/trace v1.37.0`
- `go.opentelemetry.io/otel v1.37.0`

## Proven Contract Assertions
1. `SpanIDFromHex` parses a valid 16-character lowercase hex string into a valid `SpanID` whose `String()` equals the input.
2. `SpanIDFromHex` rejects strings of length other than 16 hex characters.
3. `SpanIDFromHex` rejects uppercase hex characters per W3C trace-context requirements.
4. `SpanIDFromHex` rejects non-hex characters.
5. `SpanIDFromHex` rejects all-zero span ID (`0000000000000000`).
6. Zero-value `SpanID` is invalid (`IsValid() == false`) and formats as 16 zeros, while a parsed non-zero hex `SpanID` is valid.

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.SpanIDFromHex 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.SpanIDFromHex

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:sha256:3a01fe4adeb1e9a96d560a027dc0e304e01ffc0cd8f31fab6886db195be38644","contract":["SpanIDFromHex parses valid 16-character lowercase hex string into valid SpanID whose String matches input","SpanIDFromHex rejects strings of length other than 16 hex characters","SpanIDFromHex rejects uppercase hex characters per W3C trace-context requirements","SpanIDFromHex rejects non-hex characters","SpanIDFromHex rejects all-zero span ID string returning an error","Zero-value SpanID is invalid and formats as 16 zeros, while parsed non-zero SpanID is valid"],"goal":"verify go.opentelemetry.io/otel/trace.SpanIDFromHex 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.SpanIDFromHex"]},"contractCommand":["go","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.SpanIDFromHex"],"verifierAdapter":"golang@1"}

module sample

go 1.25.0

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

require (
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/go-logr/logr v1.4.3 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
	go.opentelemetry.io/otel v1.37.0 // indirect
	go.opentelemetry.io/otel/metric v1.37.0 // 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/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
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/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
github.com/stretchr/testify v1.12.1 h1:EuwCh5fleGS7H32xRwO3wRGT7DxrDhLAT6FF8MpWDWE=
github.com/stretchr/testify v1.12.1/go.mod h1:MDEgiDPPsNp5cuIrHPPCyornHKgEVbtFUmoNlxoYthg=
go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
go.opentelemetry.io/auto/sdk v1.1.0/go.mod h1:3wSPjt5PWp2RhlCcmmOial7AvC4DQqZb7a7wCow3W8A=
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 v1.46.0 h1:FHt5/CDyVxi/8IM1CH7VE/rRgq3kLHa2mSTVMO8AWyc=
go.opentelemetry.io/otel v1.46.0/go.mod h1:Gj3SEScelsNC45tp4nSxRYlS+f5iez7W8XPMCt905kE=
go.opentelemetry.io/otel/metric v1.37.0 h1:mvwbQS5m0tbmqML4NqK+e3aDiO02vsf/WgbsdpcPoZE=
go.opentelemetry.io/otel/metric v1.37.0/go.mod h1:04wGrZurHYKOc+RKeye86GwKiTb9FKm1WHtO+4EVr2E=
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=
go.opentelemetry.io/otel/trace v1.46.0 h1:OULy7ccdJnZtJ0UDYFOIGaCmiWzJ8Vi2G/Rsu60qs1c=
go.opentelemetry.io/otel/trace v1.46.0/go.mod h1:J7GAXweO77XSFkB/rmAqk9D6ihszhFjLU+d9WuUxDLI=
go.yaml.in/yaml/v3 v3.0.5 h1:N6y/pJk8buWs9NY5ERU2HSMfm+IuD/OtfdAnq6kESPw=
go.yaml.in/yaml/v3 v3.0.5/go.mod h1:HVTZu1O7/Vkt2N+BFy8Zza+lnLsABggaTM2ZpNIGuKg=

{
  "schemaVersion": 1,
  "goal": "verify go.opentelemetry.io/otel/trace.SpanIDFromHex 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.SpanIDFromHex"
  ]
}

package sample_test

import (
	"testing"

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

func TestSpanIDFromHex_Valid(t *testing.T) {
	validHex := "00f067aa0ba902b7"
	sid, err := trace.SpanIDFromHex(validHex)
	if err != nil {
		t.Fatalf("SpanIDFromHex failed for valid hex %q: %v", validHex, err)
	}
	if !sid.IsValid() {
		t.Fatalf("expected parsed SpanID to be valid")
	}
	if sid.String() != validHex {
		t.Fatalf("expected String() %q, got %q", validHex, sid.String())
	}
}

func TestSpanIDFromHex_InvalidLengths(t *testing.T) {
	invalidCases := []string{
		"",
		"00f0",
		"00f067aa0ba902b",       // 15 chars
		"00f067aa0ba902b70",      // 17 chars
		"00f067aa0ba902b7000000", // 22 chars
	}
	for _, tc := range invalidCases {
		if sid, err := trace.SpanIDFromHex(tc); err == nil {
			t.Fatalf("expected error for invalid length string %q, got SpanID %v", tc, sid)
		}
	}
}

func TestSpanIDFromHex_RejectsUppercaseHex(t *testing.T) {
	uppercaseHex := "00F067AA0BA902B7"
	if sid, err := trace.SpanIDFromHex(uppercaseHex); err == nil {
		t.Fatalf("expected error for uppercase hex %q, got SpanID %v", uppercaseHex, sid)
	}
}

func TestSpanIDFromHex_RejectsNonHex(t *testing.T) {
	nonHexCases := []string{
		"00f067aa0ba902bg",
		"00f067aa-ba902b7",
		"00f067aa 0ba902b",
		"zzzzzzzzzzzzzzzz",
	}
	for _, tc := range nonHexCases {
		if sid, err := trace.SpanIDFromHex(tc); err == nil {
			t.Fatalf("expected error for non-hex string %q, got SpanID %v", tc, sid)
		}
	}
}

func TestSpanIDFromHex_RejectsAllZero(t *testing.T) {
	zeroHex := "0000000000000000"
	if sid, err := trace.SpanIDFromHex(zeroHex); err == nil {
		t.Fatalf("expected error for all-zero span ID %q, got SpanID %v", zeroHex, sid)
	}
}

func TestSpanID_ValidityAndZeroValue(t *testing.T) {
	var zeroSid trace.SpanID
	if zeroSid.IsValid() {
		t.Fatalf("expected zero-value SpanID to be invalid")
	}
	if zeroSid.String() != "0000000000000000" {
		t.Fatalf("expected zero-value SpanID.String() to be 16 zeros, got %q", zeroSid.String())
	}

	validHex := "00f067aa0ba902b7"
	parsedSid, err := trace.SpanIDFromHex(validHex)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if !parsedSid.IsValid() {
		t.Fatalf("expected parsed SpanID to be valid")
	}
}