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

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.EISDIR 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.EISDIR

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:f23b4a4842a832c56631d4d5f131ebb1806e838c296080ba0f1ce85451fe2b7c","contract":["unix.EISDIR constant equals errno 21","unix.EISDIR error message equals \"is a directory\"","unix.Open on a directory with O_WRONLY fails with unix.EISDIR","unix.Read on a directory file descriptor fails with unix.EISDIR"],"goal":"verify golang.org/x/sys/unix.EISDIR 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.EISDIR"]},"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.EISDIR"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

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() {
	tmpDir, err := os.MkdirTemp("", "eisdir_demo_*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	// Attempting to open a directory for writing triggers EISDIR
	_, err = unix.Open(tmpDir, unix.O_WRONLY, 0)
	if err == nil {
		fmt.Fprintf(os.Stderr, "expected error opening directory with O_WRONLY, got nil\n")
		os.Exit(1)
	}

	if !errors.Is(err, unix.EISDIR) {
		fmt.Fprintf(os.Stderr, "expected EISDIR error, got: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Demonstrated unix.EISDIR successfully: %v (errno %d)\n", err, unix.EISDIR)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.EISDIR 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.EISDIR"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"
	"syscall"

	"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.EISDIR constant equals errno 21
	if unix.EISDIR != 21 {
		return fmt.Errorf("expected unix.EISDIR to equal 21, got %d", unix.EISDIR)
	}
	if unix.EISDIR != syscall.EISDIR {
		return fmt.Errorf("expected unix.EISDIR to equal syscall.EISDIR")
	}

	// 2. unix.EISDIR error message equals "is a directory"
	if msg := unix.EISDIR.Error(); msg != "is a directory" {
		return fmt.Errorf("expected error string %q, got %q", "is a directory", msg)
	}

	tmpDir, err := os.MkdirTemp("", "eisdir_contract_*")
	if err != nil {
		return fmt.Errorf("failed to create temp dir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	// 3. unix.Open on a directory with O_WRONLY fails with unix.EISDIR
	fd, err := unix.Open(tmpDir, unix.O_WRONLY, 0)
	if err == nil {
		unix.Close(fd)
		return fmt.Errorf("expected unix.Open with O_WRONLY on directory to fail, but it succeeded")
	}
	if !errors.Is(err, unix.EISDIR) {
		return fmt.Errorf("expected unix.Open error to match unix.EISDIR, got: %w", err)
	}

	// 4. unix.Read on a directory file descriptor fails with unix.EISDIR
	dirFd, err := unix.Open(tmpDir, unix.O_RDONLY|unix.O_DIRECTORY, 0)
	if err != nil {
		return fmt.Errorf("failed to open directory for reading: %w", err)
	}
	defer unix.Close(dirFd)

	buf := make([]byte, 16)
	_, readErr := unix.Read(dirFd, buf)
	if readErr == nil {
		return fmt.Errorf("expected unix.Read on directory to fail, but it succeeded")
	}
	if !errors.Is(readErr, unix.EISDIR) {
		return fmt.Errorf("expected unix.Read error to match unix.EISDIR, got: %w", readErr)
	}

	return nil
}