golang.org/x/net v0.0.0-20210525063256-abc453219eb5

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@v0.0.0-20210525063256-abc453219eb5
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5

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:aec8b8dfa962239fdbe9bdae16ee3444822ce0dacde77115528828fe4cf1e396","contract":["html.EscapeString and html.UnescapeString round-trip HTML special characters","atom.Lookup resolves lowercase tag names to atom.Atom constants and returns zero for unknown tags","html.Parse builds an html.Node tree with DataAtom and attributes and html.Render serializes it back to HTML"],"goal":"verify pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5"],"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@v0.0.0-20210525063256-abc453219eb5"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5","verifierAdapter":"golang@1"}

module example.com/netverify

go 1.21

require golang.org/x/net v0.0.0-20210525063256-abc453219eb5

golang.org/x/net v0.0.0-20210525063256-abc453219eb5 h1:wjuX4b5yYQnEQHzd+CBcrcC6OVR2J1CN6mUy0oSxIPo=
golang.org/x/net v0.0.0-20210525063256-abc453219eb5/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=

package netverify

import (
	"bytes"
	"strings"

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

// ParseAndRender parses HTML markup into a node tree and renders it back to string.
func ParseAndRender(markup string) (*html.Node, string, error) {
	doc, err := html.Parse(strings.NewReader(markup))
	if err != nil {
		return nil, "", err
	}
	var buf bytes.Buffer
	if err := html.Render(&buf, doc); err != nil {
		return nil, "", err
	}
	return doc, buf.String(), nil
}

// LookupAtom resolves a lowercase tag byte slice to an atom.Atom.
func LookupAtom(tag []byte) atom.Atom {
	return atom.Lookup(tag)
}

// FindFirstByAtom traverses an HTML node tree and returns the first ElementNode with DataAtom == target.
func FindFirstByAtom(root *html.Node, target atom.Atom) *html.Node {
	if root == nil {
		return nil
	}
	if root.Type == html.ElementNode && root.DataAtom == target {
		return root
	}
	for c := root.FirstChild; c != nil; c = c.NextSibling {
		if found := FindFirstByAtom(c, target); found != nil {
			return found
		}
	}
	return nil
}

// GetAttr returns the value of an attribute key on an html.Node and whether it was found.
func GetAttr(n *html.Node, key string) (string, bool) {
	if n == nil {
		return "", false
	}
	for _, a := range n.Attr {
		if a.Key == key {
			return a.Val, true
		}
	}
	return "", false
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

	"example.com/netverify"
	"golang.org/x/net/html"
	"golang.org/x/net/html/atom"
)

func main() {
	// 1. html.EscapeString and html.UnescapeString round-trip HTML special characters.
	raw := `<div class="box">&copy; "hello" 'world'</div>`
	escaped := html.EscapeString(raw)
	if !strings.Contains(escaped, "&lt;div") || !strings.Contains(escaped, "&#34;hello&#34;") {
		fmt.Fprintf(os.Stderr, "FAIL: unexpected EscapeString output: %q\n", escaped)
		os.Exit(1)
	}
	if unescaped := html.UnescapeString(escaped); unescaped != raw {
		fmt.Fprintf(os.Stderr, "FAIL: UnescapeString mismatch: got %q, want %q\n", unescaped, raw)
		os.Exit(1)
	}

	// 2. atom.Lookup resolves lowercase tag names to atom.Atom constants and returns 0 for unknown tags.
	if got := netverify.LookupAtom([]byte("article")); got != atom.Article || got.String() != "article" {
		fmt.Fprintf(os.Stderr, "FAIL: LookupAtom(\"article\") = %v (%q)\n", got, got.String())
		os.Exit(1)
	}
	if got := netverify.LookupAtom([]byte("nonexistent-tag")); got != 0 || got.String() != "" {
		fmt.Fprintf(os.Stderr, "FAIL: expected zero atom for unknown tag, got %v\n", got)
		os.Exit(1)
	}

	// 3. html.Parse builds a document tree with DataAtom and attributes, and html.Render serializes it.
	doc, rendered, err := netverify.ParseAndRender(`<!DOCTYPE html><html><body><article id="post-1"><p>content</p></article></body></html>`)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: ParseAndRender error: %v\n", err)
		os.Exit(1)
	}
	if !strings.Contains(rendered, `<article id="post-1"><p>content</p></article>`) {
		fmt.Fprintf(os.Stderr, "FAIL: unexpected rendered HTML: %q\n", rendered)
		os.Exit(1)
	}

	article := netverify.FindFirstByAtom(doc, atom.Article)
	if article == nil {
		fmt.Fprintf(os.Stderr, "FAIL: did not find article node\n")
		os.Exit(1)
	}
	if id, ok := netverify.GetAttr(article, "id"); !ok || id != "post-1" {
		fmt.Fprintf(os.Stderr, "FAIL: expected id=\"post-1\", got %q (ok=%v)\n", id, ok)
		os.Exit(1)
	}

	pNode := netverify.FindFirstByAtom(article, atom.P)
	if pNode == nil || pNode.FirstChild == nil || pNode.FirstChild.Type != html.TextNode || pNode.FirstChild.Data != "content" {
		fmt.Fprintf(os.Stderr, "FAIL: unexpected paragraph text content\n")
		os.Exit(1)
	}
}