golang.org/x/mod v0.39.0: module.CheckFilePath

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/mod/module.CheckFilePath in pkg:golang/golang.org/x/mod@v0.39.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/mod@v0.39.0
Demonstrate these symbols/APIs:
  - golang.org/x/mod/module.CheckFilePath

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:sha256:71819ba7fc82d8560b893c475ac473f2017daac3ddf941278b4bcb47d8059780","contract":["CheckFilePath returns nil for valid relative file paths","CheckFilePath returns an error for empty file path","CheckFilePath returns an error for file paths starting with a leading slash","CheckFilePath returns an error for file paths containing dot-dot path traversal","CheckFilePath returns an error for file paths containing consecutive slashes or trailing slash","CheckFilePath returns an error for file paths containing Windows reserved device names","CheckFilePath returns an error for file paths containing invalid characters"],"goal":"verify golang.org/x/mod/module.CheckFilePath in pkg:golang/golang.org/x/mod@v0.39.0","kind":"HOW","packages":["pkg:golang/golang.org/x/mod@v0.39.0"],"schemaVersion":1,"symbols":["golang.org/x/mod/module.CheckFilePath"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/mod@v0.39.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/mod@v0.39.0","symbols":["golang.org/x/mod/module.CheckFilePath"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require golang.org/x/mod v0.39.0

golang.org/x/mod v0.39.0 h1:UF5zwQdCRRUpHfyPwr7d4UrGiVeldIsogtzWVnczL74=
golang.org/x/mod v0.39.0/go.mod h1:bvIbwjQ0HUFFf5AKukeeYQG4ZBUG9yxQbR9aEweIwYY=

package main

import (
	"fmt"

	"golang.org/x/mod/module"
)

func main() {
	samplePaths := []string{
		"pkg/sub/file.go",
		"README.md",
		"/absolute/path.go",
		"../traversal.go",
		"CON",
	}

	for _, p := range samplePaths {
		if err := module.CheckFilePath(p); err != nil {
			fmt.Printf("Path %q is invalid: %v\n", p, err)
		} else {
			fmt.Printf("Path %q is valid\n", p)
		}
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/mod/module.CheckFilePath in pkg:golang/golang.org/x/mod@v0.39.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/mod@v0.39.0"
  ],
  "symbols": [
    "golang.org/x/mod/module.CheckFilePath"
  ]
}

package main

import (
	"fmt"
	"os"

	"golang.org/x/mod/module"
)

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

func runTests() error {
	// 1. CheckFilePath returns nil for valid relative file paths
	{
		validPaths := []string{
			"README.md",
			"pkg/sub/file.go",
			"dir/file-1.0.txt",
			"src/main_test.go",
		}
		for _, p := range validPaths {
			if err := module.CheckFilePath(p); err != nil {
				return fmt.Errorf("expected valid path %q to succeed, got error: %w", p, err)
			}
		}
	}

	// 2. CheckFilePath returns an error for empty file path
	{
		if err := module.CheckFilePath(""); err == nil {
			return fmt.Errorf("expected empty path to return error, got nil")
		}
	}

	// 3. CheckFilePath returns an error for file paths starting with a leading slash
	{
		if err := module.CheckFilePath("/absolute/path.go"); err == nil {
			return fmt.Errorf("expected leading slash path to return error, got nil")
		}
	}

	// 4. CheckFilePath returns an error for file paths containing dot-dot path traversal
	{
		invalidPaths := []string{
			"../file.go",
			"dir/../file.go",
			"dir/..",
		}
		for _, p := range invalidPaths {
			if err := module.CheckFilePath(p); err == nil {
				return fmt.Errorf("expected path traversal %q to return error, got nil", p)
			}
		}
	}

	// 5. CheckFilePath returns an error for file paths containing consecutive slashes or trailing slash
	{
		invalidPaths := []string{
			"dir//file.go",
			"dir/file.go/",
		}
		for _, p := range invalidPaths {
			if err := module.CheckFilePath(p); err == nil {
				return fmt.Errorf("expected malformed slash path %q to return error, got nil", p)
			}
		}
	}

	// 6. CheckFilePath returns an error for file paths containing Windows reserved device names
	{
		reservedPaths := []string{
			"CON",
			"aux.txt",
			"dir/NUL",
			"dir/com1.go",
		}
		for _, p := range reservedPaths {
			if err := module.CheckFilePath(p); err == nil {
				return fmt.Errorf("expected Windows reserved path %q to return error, got nil", p)
			}
		}
	}

	// 7. CheckFilePath returns an error for file paths containing invalid characters
	{
		invalidCharPaths := []string{
			"dir\\file.go",
			"dir:file.go",
			"dir*file.go",
		}
		for _, p := range invalidCharPaths {
			if err := module.CheckFilePath(p); err == nil {
				return fmt.Errorf("expected invalid character path %q to return error, got nil", p)
			}
		}
	}

	return nil
}