golang.org/x/sys v0.22.0: unix.EEXIST

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 golang.org/x/sys/unix.EEXIST in pkg:golang/golang.org/x/sys@v0.22.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.22.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.EEXIST

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:sha256:7b3d7b44e3c3aae1f835cc542c5248c4522269e60714ec0d754f0d5478a0174a","contract":["unix.EEXIST error number equals 17 and Error() returns file exists","unix.Open with O_CREAT and O_EXCL returns unix.EEXIST when file already exists","unix.Mkdir returns unix.EEXIST when directory path already exists"],"goal":"verify golang.org/x/sys/unix.EEXIST in pkg:golang/golang.org/x/sys@v0.22.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.22.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.EEXIST"]},"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/golang.org/x/sys@v0.22.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.22.0","symbols":["golang.org/x/sys/unix.EEXIST"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22

require golang.org/x/sys v0.22.0

golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	tmpFile, err := os.CreateTemp("", "eexist_demo_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp file: %v\n", err)
		os.Exit(1)
	}
	defer os.Remove(tmpFile.Name())
	tmpFile.Close()

	_, err = unix.Open(tmpFile.Name(), unix.O_CREAT|unix.O_EXCL|unix.O_RDWR, 0600)
	if errors.Is(err, unix.EEXIST) {
		fmt.Printf("Successfully encountered unix.EEXIST: %v\n", err)
	} else {
		fmt.Fprintf(os.Stderr, "expected unix.EEXIST, got: %v\n", err)
		os.Exit(1)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.EEXIST in pkg:golang/golang.org/x/sys@v0.22.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.22.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.EEXIST"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	if err := runTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract assertions passed.")
}

func runTests() error {
	// 1. unix.EEXIST error number equals 17 and Error() returns file exists
	if unix.EEXIST != 17 {
		return fmt.Errorf("expected unix.EEXIST to be 17, got %d", int(unix.EEXIST))
	}
	if unix.EEXIST.Error() != "file exists" {
		return fmt.Errorf("expected unix.EEXIST.Error() to be 'file exists', got '%s'", unix.EEXIST.Error())
	}

	// 2. unix.Open with O_CREAT and O_EXCL returns unix.EEXIST when file already exists
	tmpFile, err := os.CreateTemp("", "eexist_test_*")
	if err != nil {
		return fmt.Errorf("failed to create temporary file: %w", err)
	}
	tmpFileName := tmpFile.Name()
	tmpFile.Close()
	defer os.Remove(tmpFileName)

	fd, err := unix.Open(tmpFileName, unix.O_CREAT|unix.O_EXCL|unix.O_RDWR, 0600)
	if err == nil {
		unix.Close(fd)
		return fmt.Errorf("expected unix.Open to fail with unix.EEXIST, but succeeded")
	}
	if !errors.Is(err, unix.EEXIST) {
		return fmt.Errorf("expected unix.EEXIST, got %v", err)
	}

	// 3. unix.Mkdir returns unix.EEXIST when directory path already exists
	tmpDir, err := os.MkdirTemp("", "eexist_dir_*")
	if err != nil {
		return fmt.Errorf("failed to create temporary directory: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	err = unix.Mkdir(tmpDir, 0755)
	if err == nil {
		return fmt.Errorf("expected unix.Mkdir to fail with unix.EEXIST, but succeeded")
	}
	if !errors.Is(err, unix.EEXIST) {
		return fmt.Errorf("expected unix.EEXIST, got %v", err)
	}

	return nil
}