golang.org/x/mod v0.33.0: module.CheckImportPath

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.CheckImportPath in pkg:golang/golang.org/x/mod@v0.33.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/mod@v0.33.0
Demonstrate these symbols/APIs:
  - golang.org/x/mod/module.CheckImportPath

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:sha256:5bf3165ca35e93b72718fb2ced0b37464b622e7dc71ee7101562f8a0df3d8d4b","contract":["module.CheckImportPath returns nil for valid standard library and domain-prefixed import paths","module.CheckImportPath rejects an empty path with *module.InvalidPathError having Kind set to import","module.CheckImportPath rejects import paths with leading, trailing, or consecutive slashes","module.CheckImportPath rejects relative import paths and dot path elements","module.CheckImportPath rejects import paths containing Windows reserved names or invalid characters"],"goal":"verify golang.org/x/mod/module.CheckImportPath in pkg:golang/golang.org/x/mod@v0.33.0","kind":"HOW","packages":["pkg:golang/golang.org/x/mod@v0.33.0"],"schemaVersion":1,"symbols":["golang.org/x/mod/module.CheckImportPath"]},"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@v0.33.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/mod@v0.33.0","symbols":["golang.org/x/mod/module.CheckImportPath"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/mod v0.33.0

golang.org/x/mod v0.33.0 h1:tHFzIWbBifEmbwtGz65eaWyGiGZatSrT9prnU8DbVL8=
golang.org/x/mod v0.33.0/go.mod h1:swjeQEj+6r7fODbD2cqrnje9PnziFuw4bmLbBZFrQ5w=

package main

import (
	"fmt"
	"os"

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

func main() {
	if err := module.CheckImportPath("example.com/pkg/sub"); err != nil {
		fmt.Fprintf(os.Stderr, "unexpected error for valid import path: %v\n", err)
		os.Exit(1)
	}
	if err := module.CheckImportPath("../invalid"); err == nil {
		fmt.Fprintln(os.Stderr, "expected error for invalid import path, got nil")
		os.Exit(1)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/mod/module.CheckImportPath in pkg:golang/golang.org/x/mod@v0.33.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/mod@v0.33.0"
  ],
  "symbols": [
    "golang.org/x/mod/module.CheckImportPath"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

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

func main() {
	// 1. Valid import paths return nil
	validImportPaths := []string{
		"fmt",
		"encoding/json",
		"example.com/pkg",
		"example.com/pkg/sub/v2",
	}
	for _, p := range validImportPaths {
		if err := module.CheckImportPath(p); err != nil {
			fmt.Fprintf(os.Stderr, "CheckImportPath(%q) failed unexpectedly: %v\n", p, err)
			os.Exit(1)
		}
	}

	// 2. Empty import path returns *module.InvalidPathError with Kind == "import"
	err := module.CheckImportPath("")
	if err == nil {
		fmt.Fprintln(os.Stderr, "CheckImportPath(\"\") returned nil, expected error")
		os.Exit(1)
	}
	var pathErr *module.InvalidPathError
	if !errors.As(err, &pathErr) || pathErr.Kind != "import" || pathErr.Path != "" {
		fmt.Fprintf(os.Stderr, "CheckImportPath(\"\") returned unexpected error structure: %#v\n", err)
		os.Exit(1)
	}

	// 3. Import paths with leading, trailing, or consecutive slashes are rejected
	for _, p := range []string{"/example.com/pkg", "example.com/pkg/", "example.com//pkg"} {
		if err := module.CheckImportPath(p); err == nil {
			fmt.Fprintf(os.Stderr, "CheckImportPath(%q) returned nil, expected slash error\n", p)
			os.Exit(1)
		}
	}

	// 4. Relative import paths and dot segments are rejected
	for _, p := range []string{".", "..", "./pkg", "../pkg", "example.com/./pkg", "example.com/../pkg"} {
		if err := module.CheckImportPath(p); err == nil {
			fmt.Fprintf(os.Stderr, "CheckImportPath(%q) returned nil, expected dot segment error\n", p)
			os.Exit(1)
		}
	}

	// 5. Windows reserved names and invalid characters are rejected
	for _, p := range []string{"example.com/con", "example.com/nul.txt", "example.com/bad path", "example.com/bad:path"} {
		if err := module.CheckImportPath(p); err == nil {
			fmt.Fprintf(os.Stderr, "CheckImportPath(%q) returned nil, expected invalid element error\n", p)
			os.Exit(1)
		}
	}
}