go.step.sm/crypto v0.89.0: randutil.UUIDv4

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.step.sm/crypto/randutil.UUIDv4 in pkg:golang/go.step.sm/crypto@v0.89.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.step.sm/crypto@v0.89.0
Demonstrate these symbols/APIs:
  - go.step.sm/crypto/randutil.UUIDv4

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:sha256:24d2a5da7fb3f2d60d80b081dc56a57629f8f2f1c77623d6990da3b72bf0f8da","contract":["randutil.UUIDv4 returns a string with valid RFC 4122 format of 36 characters","randutil.UUIDv4 sets the version 4 bits and RFC 4122 variant bits","randutil.UUIDv4 produces unique identifiers across consecutive calls","randutil.UUIDv4 returns nil error under normal conditions"],"goal":"verify go.step.sm/crypto/randutil.UUIDv4 in pkg:golang/go.step.sm/crypto@v0.89.0","kind":"HOW","packages":["pkg:golang/go.step.sm/crypto@v0.89.0"],"schemaVersion":1,"symbols":["go.step.sm/crypto/randutil.UUIDv4"]},"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.step.sm/crypto@v0.89.0"],"schemaVersion":1,"subject":"pkg:golang/go.step.sm/crypto@v0.89.0","symbols":["go.step.sm/crypto/randutil.UUIDv4"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require go.step.sm/crypto v0.89.0

require github.com/pkg/errors v0.9.1 // indirect

github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/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.step.sm/crypto v0.89.0 h1:NPxryE+cZ4XDwXOQY2U6Gu+mOzOihuRLPIsX7WtPzZM=
go.step.sm/crypto v0.89.0/go.mod h1:IEgE6DndnYojbDyHU7eYXpwWzpu4ftkouw7nyI6jsxg=
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 (
	"fmt"
	"log"

	"go.step.sm/crypto/randutil"
)

func main() {
	id, err := randutil.UUIDv4()
	if err != nil {
		log.Fatalf("failed to generate UUIDv4: %v", err)
	}
	fmt.Printf("Generated UUIDv4: %s\n", id)
}

{
  "schemaVersion": 1,
  "goal": "verify go.step.sm/crypto/randutil.UUIDv4 in pkg:golang/go.step.sm/crypto@v0.89.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.step.sm/crypto@v0.89.0"
  ],
  "symbols": [
    "go.step.sm/crypto/randutil.UUIDv4"
  ]
}

package main

import (
	"fmt"
	"os"
	"regexp"

	"go.step.sm/crypto/randutil"
)

var uuidv4Regex = regexp.MustCompile(`^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$`)

func main() {
	// Assertion 1: randutil.UUIDv4 returns a string with valid RFC 4122 format of 36 characters
	uuid, err := randutil.UUIDv4()
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: randutil.UUIDv4 returned error: %v\n", err)
		os.Exit(1)
	}
	if len(uuid) != 36 {
		fmt.Fprintf(os.Stderr, "FAIL: expected UUID length 36, got %d: %q\n", len(uuid), uuid)
		os.Exit(1)
	}
	if !uuidv4Regex.MatchString(uuid) {
		fmt.Fprintf(os.Stderr, "FAIL: UUID %q does not match RFC 4122 v4 pattern\n", uuid)
		os.Exit(1)
	}
	if uuid[8] != '-' || uuid[13] != '-' || uuid[18] != '-' || uuid[23] != '-' {
		fmt.Fprintf(os.Stderr, "FAIL: invalid hyphen positions in UUID %q\n", uuid)
		os.Exit(1)
	}

	// Assertion 2: randutil.UUIDv4 sets the version 4 bits and RFC 4122 variant bits
	if uuid[14] != '4' {
		fmt.Fprintf(os.Stderr, "FAIL: expected version '4' at index 14, got %c in %q\n", uuid[14], uuid)
		os.Exit(1)
	}
	variantChar := uuid[19]
	if variantChar != '8' && variantChar != '9' && variantChar != 'a' && variantChar != 'b' {
		fmt.Fprintf(os.Stderr, "FAIL: expected variant char [89ab] at index 19, got %c in %q\n", variantChar, uuid)
		os.Exit(1)
	}

	// Assertion 3: randutil.UUIDv4 produces unique identifiers across consecutive calls
	seen := make(map[string]bool)
	const sampleCount = 100
	for i := 0; i < sampleCount; i++ {
		val, err := randutil.UUIDv4()
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: randutil.UUIDv4 error on iteration %d: %v\n", i, err)
			os.Exit(1)
		}
		if !uuidv4Regex.MatchString(val) {
			fmt.Fprintf(os.Stderr, "FAIL: iteration %d generated invalid UUIDv4 %q\n", i, val)
			os.Exit(1)
		}
		if seen[val] {
			fmt.Fprintf(os.Stderr, "FAIL: duplicate UUID %q generated at iteration %d\n", val, i)
			os.Exit(1)
		}
		seen[val] = true
	}
	if len(seen) != sampleCount {
		fmt.Fprintf(os.Stderr, "FAIL: expected %d unique UUIDs, got %d\n", sampleCount, len(seen))
		os.Exit(1)
	}

	// Assertion 4: randutil.UUIDv4 returns nil error under normal conditions
	testVal, testErr := randutil.UUIDv4()
	if testErr != nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected nil error, got %v\n", testErr)
		os.Exit(1)
	}
	if testVal == "" {
		fmt.Fprintf(os.Stderr, "FAIL: expected non-empty UUID string, got empty\n")
		os.Exit(1)
	}

	fmt.Println("PASS: all randutil.UUIDv4 contract assertions passed")
}