golang.org/x/net v0.25.0: html.Parse, html.Render, 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 pkg:golang/golang.org/x/net@v0.25.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.25.0

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:sha256:7fdbf9d3e1b1e4fe1726fd244b35ba96e64fdf16564d6ec2db3b97f8a54b8caa","contract":["html.Parse parses an HTML document into a node tree to extract the document title and anchor href attributes","html.Render serializes a parsed html.Node tree back into valid HTML while preserving escaped entities","publicsuffix.PublicSuffix and publicsuffix.EffectiveTLDPlusOne resolve the ICANN public suffix and registrable domain and reject bare suffixes"],"goal":"verify pkg:golang/golang.org/x/net@v0.25.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.25.0"],"schemaVersion":1,"symbols":["html.Parse","html.Render","publicsuffix.EffectiveTLDPlusOne","publicsuffix.PublicSuffix"]},"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@v0.25.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.25.0","symbols":["html.Parse","html.Render","publicsuffix.EffectiveTLDPlusOne","publicsuffix.PublicSuffix"],"verifierAdapter":"golang@1"}

module example.com/xnet-sample

go 1.21

require golang.org/x/net v0.25.0

golang.org/x/net v0.25.0 h1:d/OCCoBEUq33pjydKrGQhw7IlUPI2Oylr+8qLx49kac=
golang.org/x/net v0.25.0/go.mod h1:JkAGAh7GEvH74S6FOH42FLoXpXbE/aqXSrIQjXgsiwM=

package main

import (
	"bytes"
	"fmt"
	"strings"

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

func ExtractLinks(rawHTML string) ([]string, string, error) {
	doc, err := html.Parse(strings.NewReader(rawHTML))
	if err != nil {
		return nil, "", err
	}
	var links []string
	var walk func(*html.Node)
	walk = func(n *html.Node) {
		if n.Type == html.ElementNode && n.Data == "a" {
			for _, attr := range n.Attr {
				if attr.Key == "href" {
					links = append(links, attr.Val)
				}
			}
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			walk(c)
		}
	}
	walk(doc)

	var buf bytes.Buffer
	if err := html.Render(&buf, doc); err != nil {
		return nil, "", err
	}
	return links, buf.String(), nil
}

func ResolveDomain(host string) (suffix string, icann bool, etldPlusOne string, err error) {
	suffix, icann = publicsuffix.PublicSuffix(host)
	etldPlusOne, err = publicsuffix.EffectiveTLDPlusOne(host)
	return suffix, icann, etldPlusOne, err
}

func main() {
	links, _, err := ExtractLinks(`<p><a href="https://example.com/docs">Docs</a></p>`)
	if err != nil {
		panic(err)
	}
	suffix, icann, root, err := ResolveDomain("sub.example.co.uk")
	if err != nil {
		panic(err)
	}
	fmt.Printf("links=%v suffix=%s icann=%v root=%s\n", links, suffix, icann, root)
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/golang.org/x/net@v0.25.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.25.0"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"
	"strings"

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

func fail(format string, args ...any) {
	fmt.Fprintf(os.Stderr, format+"\n", args...)
	os.Exit(1)
}

func main() {
	const inputHTML = `<!DOCTYPE html><html><head><title>Sample &amp; Test</title></head><body><a href="https://example.com/a">First</a><a href="/b">Second</a></body></html>`
	doc, err := html.Parse(strings.NewReader(inputHTML))
	if err != nil {
		fail("html.Parse failed: %v", err)
	}

	var title string
	var hrefs []string
	var visit func(*html.Node)
	visit = func(n *html.Node) {
		if n.Type == html.ElementNode {
			if n.Data == "title" && n.FirstChild != nil && n.FirstChild.Type == html.TextNode {
				title = n.FirstChild.Data
			}
			if n.Data == "a" {
				for _, a := range n.Attr {
					if a.Key == "href" {
						hrefs = append(hrefs, a.Val)
					}
				}
			}
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			visit(c)
		}
	}
	visit(doc)

	if title != "Sample & Test" {
		fail("unexpected title: got %q, want %q", title, "Sample & Test")
	}
	if len(hrefs) != 2 || hrefs[0] != "https://example.com/a" || hrefs[1] != "/b" {
		fail("unexpected hrefs: got %v", hrefs)
	}

	var rendered bytes.Buffer
	if err := html.Render(&rendered, doc); err != nil {
		fail("html.Render failed: %v", err)
	}
	if !strings.Contains(rendered.String(), "<title>Sample &amp; Test</title>") {
		fail("rendered HTML did not preserve escaped title: %s", rendered.String())
	}

	suffix, icann := publicsuffix.PublicSuffix("api.sub.example.co.uk")
	if suffix != "co.uk" || !icann {
		fail("PublicSuffix(api.sub.example.co.uk) = (%q, %v), want (\"co.uk\", true)", suffix, icann)
	}

	etld1, err := publicsuffix.EffectiveTLDPlusOne("api.sub.example.co.uk")
	if err != nil || etld1 != "example.co.uk" {
		fail("EffectiveTLDPlusOne(api.sub.example.co.uk) = (%q, %v), want (\"example.co.uk\", nil)", etld1, err)
	}

	if _, err := publicsuffix.EffectiveTLDPlusOne("co.uk"); err == nil {
		fail("expected EffectiveTLDPlusOne(\"co.uk\") to fail for bare public suffix")
	}
}