golang.org/x/net v0.41.0

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@v0.41.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.41.0

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:sha256:5c40f1965791a19bfbc44f1de0c7414f2e73a7041d1d4b1ba61dd7652a6ab42e","contract":["html.Parse parses an HTML5 document into a tree of *html.Node with resolved DataAtom values","Traversing parsed nodes resolves atom.Div, atom.P, and atom.A elements and their attributes/text","atom.Lookup resolves known lowercase HTML tag names and returns 0 for unknown or uppercase names","html.Render serializes constructed *html.Node trees and escapes special characters in text and attributes","html.EscapeString and html.UnescapeString round-trip HTML entities accurately"],"goal":"verify pkg:golang/golang.org/x/net@v0.41.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.41.0"],"schemaVersion":1},"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@v0.41.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.41.0","verifierAdapter":"golang@1"}

module example.com/sample

go 1.23.0

require golang.org/x/net v0.41.0

golang.org/x/net v0.41.0 h1:vBTly1HeNPEn3wtREYfy4GZ/NECgw2Cnl+nK6Nz3uvw=
golang.org/x/net v0.41.0/go.mod h1:B/K4NNqkfmg07DQYrbwvSluqCJOOXwUjeb/5lOisjbA=

package main

import (
	"bytes"
	"fmt"
	"strings"

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

func main() {
	rawHTML := `<!DOCTYPE html><html><head><title>Sample</title></head><body><div id="main"><p>Hello, world!</p><a href="https://example.com/docs">Docs</a></div></body></html>`
	doc, err := html.Parse(strings.NewReader(rawHTML))
	if err != nil {
		panic(err)
	}

	var paragraphText string
	var linkHref string
	var walk func(*html.Node)
	walk = func(n *html.Node) {
		if n.Type == html.ElementNode {
			switch n.DataAtom {
			case atom.P:
				if n.FirstChild != nil && n.FirstChild.Type == html.TextNode {
					paragraphText = n.FirstChild.Data
				}
			case atom.A:
				for _, attr := range n.Attr {
					if attr.Key == "href" {
						linkHref = attr.Val
					}
				}
			}
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			walk(c)
		}
	}
	walk(doc)

	fmt.Printf("Paragraph: %s\n", paragraphText)
	fmt.Printf("Link: %s\n", linkHref)

	section := &html.Node{
		Type:     html.ElementNode,
		DataAtom: atom.Section,
		Data:     atom.Section.String(),
		Attr:     []html.Attribute{{Key: "class", Val: "summary"}},
	}
	span := &html.Node{
		Type:     html.ElementNode,
		DataAtom: atom.Span,
		Data:     atom.Span.String(),
	}
	span.AppendChild(&html.Node{
		Type: html.TextNode,
		Data: "Rendered output",
	})
	section.AppendChild(span)

	var buf bytes.Buffer
	if err := html.Render(&buf, section); err != nil {
		panic(err)
	}
	fmt.Printf("Rendered: %s\n", buf.String())
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/golang.org/x/net@v0.41.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.41.0"
  ]
}

package main

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

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

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

func main() {
	// 1. html.Parse parses an HTML5 document into a tree of *html.Node with resolved DataAtom values
	src := `<!DOCTYPE html><html><head><title>Title</title></head><body><div id="box"><p>Text</p><a href="https://example.com/item">Link</a></div></body></html>`
	doc, err := html.Parse(strings.NewReader(src))
	if err != nil {
		fail("assertion 1 failed: html.Parse returned error: %v", err)
	}
	if doc == nil || doc.Type != html.DocumentNode {
		fail("assertion 1 failed: expected root DocumentNode")
	}

	// 2. Traversing parsed nodes resolves atom.Div, atom.P, and atom.A elements and their attributes/text
	var foundDiv, foundP, foundA bool
	var hrefVal, pText string
	var walk func(*html.Node)
	walk = func(n *html.Node) {
		if n.Type == html.ElementNode {
			switch n.DataAtom {
			case atom.Div:
				for _, a := range n.Attr {
					if a.Key == "id" && a.Val == "box" {
						foundDiv = true
					}
				}
			case atom.P:
				foundP = true
				if n.FirstChild != nil && n.FirstChild.Type == html.TextNode {
					pText = n.FirstChild.Data
				}
			case atom.A:
				foundA = true
				for _, a := range n.Attr {
					if a.Key == "href" {
						hrefVal = a.Val
					}
				}
			}
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			walk(c)
		}
	}
	walk(doc)
	if !foundDiv || !foundP || !foundA {
		fail("assertion 2 failed: missing expected elements (div=%v, p=%v, a=%v)", foundDiv, foundP, foundA)
	}
	if pText != "Text" || hrefVal != "https://example.com/item" {
		fail("assertion 2 failed: unexpected text=%q or href=%q", pText, hrefVal)
	}

	// 3. atom.Lookup resolves known lowercase HTML tag names and returns 0 for unknown or uppercase names
	if atom.Lookup([]byte("section")) != atom.Section {
		fail("assertion 3 failed: expected atom.Section for 'section'")
	}
	if atom.Lookup([]byte("SECTION")) != 0 {
		fail("assertion 3 failed: expected 0 for uppercase 'SECTION'")
	}

	// 4. html.Render serializes constructed *html.Node trees and escapes special characters in text and attributes
	container := &html.Node{
		Type:     html.ElementNode,
		DataAtom: atom.Div,
		Data:     atom.Div.String(),
		Attr:     []html.Attribute{{Key: "data-label", Val: `a"b`}},
	}
	container.AppendChild(&html.Node{
		Type: html.TextNode,
		Data: "<tag>&value",
	})
	var rendered bytes.Buffer
	if err := html.Render(&rendered, container); err != nil {
		fail("assertion 4 failed: html.Render returned error: %v", err)
	}
	expected := `<div data-label="a&#34;b">&lt;tag&gt;&amp;value</div>`
	if rendered.String() != expected {
		fail("assertion 4 failed: expected %q, got %q", expected, rendered.String())
	}

	// 5. html.EscapeString and html.UnescapeString round-trip HTML entities accurately
	raw := `<script attr="val">'test' & more</script>`
	escaped := html.EscapeString(raw)
	if !strings.Contains(escaped, "&lt;script") || !strings.Contains(escaped, "&amp;") {
		fail("assertion 5 failed: EscapeString did not escape: %q", escaped)
	}
	if html.UnescapeString(escaped) != raw {
		fail("assertion 5 failed: UnescapeString did not round-trip: %q", html.UnescapeString(escaped))
	}
}