golang.org/x/mod v0.39.0: 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@v0.39.0
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.CheckImportPath
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:48a216f49bf021c909cb2a07854b07405476265afdcb36b8c817f3251fc6e34c","contract":["module.CheckImportPath accepts valid standard and custom import paths returning nil","module.CheckImportPath rejects empty import path with module.InvalidPathError having Kind import","module.CheckImportPath rejects import paths with leading or trailing slashes","module.CheckImportPath rejects relative import paths beginning with dot or double dots","module.CheckImportPath rejects import paths containing Windows reserved file names","module.CheckImportPath rejects import paths containing invalid punctuation or whitespace"],"goal":"verify golang.org/x/mod/module.CheckImportPath 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.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@v0.39.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/mod@v0.39.0","symbols":["golang.org/x/mod/module.CheckImportPath"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/mod v0.39.0

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

package main

import (
	"fmt"
	"os"

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

func main() {
	validPath := "golang.org/x/mod/module"
	if err := module.CheckImportPath(validPath); err != nil {
		fmt.Fprintf(os.Stderr, "CheckImportPath(%q) unexpected error: %v\n", validPath, err)
		os.Exit(1)
	}
	fmt.Printf("valid import path %q passed check\n", validPath)

	invalidPath := "golang.org/x/mod//module"
	if err := module.CheckImportPath(invalidPath); err == nil {
		fmt.Fprintf(os.Stderr, "CheckImportPath(%q) expected error, got nil\n", invalidPath)
		os.Exit(1)
	} else {
		fmt.Printf("invalid import path %q correctly rejected: %v\n", invalidPath, err)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/mod/module.CheckImportPath 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.CheckImportPath"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"errors"
	"fmt"
	"os"

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

func main() {
	// Contract 1: module.CheckImportPath accepts valid standard and custom import paths returning nil
	validPaths := []string{
		"fmt",
		"net/http",
		"golang.org/x/mod/module",
		"example.com/user/pkg",
		"x.y/z/v2",
	}
	for _, p := range validPaths {
		if err := module.CheckImportPath(p); err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) returned unexpected error: %v\n", p, err)
			os.Exit(1)
		}
	}

	// Contract 2: module.CheckImportPath rejects empty import path with module.InvalidPathError having Kind import
	emptyErr := module.CheckImportPath("")
	if emptyErr == nil {
		fmt.Fprintln(os.Stderr, "FAIL: CheckImportPath(\"\") succeeded, expected error")
		os.Exit(1)
	}
	var emptyInvalidErr *module.InvalidPathError
	if !errors.As(emptyErr, &emptyInvalidErr) {
		fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(\"\") returned error type %T, want *module.InvalidPathError\n", emptyErr)
		os.Exit(1)
	}
	if emptyInvalidErr.Kind != "import" {
		fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(\"\") returned Kind %q, want \"import\"\n", emptyInvalidErr.Kind)
		os.Exit(1)
	}

	// Contract 3: module.CheckImportPath rejects import paths with leading or trailing slashes
	slashPaths := []string{
		"/golang.org/x/mod",
		"golang.org/x/mod/",
		"golang.org//x/mod",
	}
	for _, p := range slashPaths {
		err := module.CheckImportPath(p)
		if err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) succeeded, expected slash error\n", p)
			os.Exit(1)
		}
		var slashInvalidErr *module.InvalidPathError
		if !errors.As(err, &slashInvalidErr) || slashInvalidErr.Kind != "import" {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) returned unexpected error: %v\n", p, err)
			os.Exit(1)
		}
	}

	// Contract 4: module.CheckImportPath rejects relative import paths beginning with dot or double dots
	relativePaths := []string{
		".",
		"..",
		"./pkg",
		"../pkg",
		"example.com/pkg/../other",
	}
	for _, p := range relativePaths {
		err := module.CheckImportPath(p)
		if err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) succeeded, expected relative path error\n", p)
			os.Exit(1)
		}
	}

	// Contract 5: module.CheckImportPath rejects import paths containing Windows reserved file names
	reservedPaths := []string{
		"example.com/nul",
		"example.com/con/pkg",
		"example.com/aux.txt",
		"example.com/com1",
	}
	for _, p := range reservedPaths {
		err := module.CheckImportPath(p)
		if err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) succeeded, expected reserved name error\n", p)
			os.Exit(1)
		}
	}

	// Contract 6: module.CheckImportPath rejects import paths containing invalid punctuation or whitespace
	invalidCharPaths := []string{
		"example.com/foo bar",
		"example.com/foo\\bar",
		"example.com/foo:bar",
		"example.com/foo?bar",
	}
	for _, p := range invalidCharPaths {
		err := module.CheckImportPath(p)
		if err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: CheckImportPath(%q) succeeded, expected invalid char error\n", p)
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed.")
}