golang.org/x/net v0.12.0: publicsuffix.EffectiveTLDPlusOne

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/net/publicsuffix.EffectiveTLDPlusOne in pkg:golang/golang.org/x/net@v0.12.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.12.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/publicsuffix.EffectiveTLDPlusOne

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:sha256:891aa4e65576d6c287bc13676aa788a440e9329c5f8ee6428366d703fd411740","contract":["publicsuffix.EffectiveTLDPlusOne extracts the effective top-level domain plus one label, or returns an error for invalid domains"],"goal":"verify golang.org/x/net/publicsuffix.EffectiveTLDPlusOne in pkg:golang/golang.org/x/net@v0.12.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.12.0"],"schemaVersion":1,"symbols":["golang.org/x/net/publicsuffix.EffectiveTLDPlusOne"]},"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/net@v0.12.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.12.0","symbols":["golang.org/x/net/publicsuffix.EffectiveTLDPlusOne"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.20

require golang.org/x/net v0.12.0

golang.org/x/net v0.12.0 h1:cfawfvKITfUsFCeJIHJrbSxpeu/E81khclypR0GVT50=
golang.org/x/net v0.12.0/go.mod h1:zEVYFnQC7m/vmpQFELhcD1EWkZlX69l4oqgmer6hfKA=

package main

import (
	"fmt"
	"log"

	"golang.org/x/net/publicsuffix"
)

func main() {
	domain := "subdomain.example.com"
	etldPlusOne, err := publicsuffix.EffectiveTLDPlusOne(domain)
	if err != nil {
		log.Fatalf("failed to extract eTLD+1: %v", err)
	}
	fmt.Printf("Domain: %s -> eTLD+1: %s\n", domain, etldPlusOne)

	fmt.Println("golang.org/x/net/publicsuffix sample completed successfully")
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/publicsuffix.EffectiveTLDPlusOne in pkg:golang/golang.org/x/net@v0.12.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.12.0"
  ],
  "symbols": [
    "golang.org/x/net/publicsuffix.EffectiveTLDPlusOne"
  ]
}

package main

import (
	"fmt"
	"os"

	"golang.org/x/net/publicsuffix"
)

func main() {
	// Assertion: publicsuffix.EffectiveTLDPlusOne extracts the effective top-level domain plus one label, or returns an error for invalid domains
	validCases := []struct {
		domain  string
		wantDom string
	}{
		{"example.com", "example.com"},
		{"sub.example.com", "example.com"},
		{"a.b.c.example.co.uk", "example.co.uk"},
		{"foo.github.io", "foo.github.io"},
		{"sub.foo.github.io", "foo.github.io"},
	}

	for _, tc := range validCases {
		gotDom, err := publicsuffix.EffectiveTLDPlusOne(tc.domain)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion failed for %q: unexpected error: %v\n", tc.domain, err)
			os.Exit(1)
		}
		if gotDom != tc.wantDom {
			fmt.Fprintf(os.Stderr, "assertion failed for %q: got %q, want %q\n", tc.domain, gotDom, tc.wantDom)
			os.Exit(1)
		}
	}

	invalidCases := []string{
		"com",
		"co.uk",
		"github.io",
		"",
		".",
		"..",
	}

	for _, inv := range invalidCases {
		gotDom, err := publicsuffix.EffectiveTLDPlusOne(inv)
		if err == nil {
			fmt.Fprintf(os.Stderr, "assertion failed for invalid domain %q: expected error, got %q\n", inv, gotDom)
			os.Exit(1)
		}
	}

	fmt.Println("PASS: publicsuffix.EffectiveTLDPlusOne contract passed")
}