golang.org/x/net v0.55.0: html.EscapeString, html.Parse, html.Render

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/html Parse, Render, and EscapeString in pkg:golang/golang.org/x/net@v0.55.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.55.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/html.EscapeString
  - golang.org/x/net/html.Parse
  - golang.org/x/net/html.Render

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:b9902c1fa57d5fe59cf642b2e606b34c4c7e7d80f39cdf996a3df429f5b26b6c","contract":["html.EscapeString escapes special characters like ampersands, angle brackets, and quotes for safe HTML insertion","html.Parse parses an HTML document into a DocumentNode tree with correct node hierarchy and attributes","html.Render serializes an HTML node tree back into formatted HTML written to an io.Writer"],"goal":"verify golang.org/x/net/html Parse, Render, and EscapeString in pkg:golang/golang.org/x/net@v0.55.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.55.0"],"schemaVersion":1,"symbols":["golang.org/x/net/html.EscapeString","golang.org/x/net/html.Parse","golang.org/x/net/html.Render"]},"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@v0.55.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.55.0","symbols":["golang.org/x/net/html.EscapeString","golang.org/x/net/html.Parse","golang.org/x/net/html.Render"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.25.0

require golang.org/x/net v0.55.0

golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=

package main

import (
	"bytes"
	"fmt"
	"log"
	"strings"

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

func main() {
	rawHTML := `<div class="container"><p>Hello &amp; welcome &lt;friends&gt;!</p></div>`

	rawText := "Tom & Jerry <cartoon>"
	escaped := html.EscapeString(rawText)
	fmt.Printf("Escaped: %s\n", escaped)

	doc, err := html.Parse(strings.NewReader(rawHTML))
	if err != nil {
		log.Fatalf("failed to parse HTML: %v", err)
	}

	var buf bytes.Buffer
	if err := html.Render(&buf, doc); err != nil {
		log.Fatalf("failed to render HTML: %v", err)
	}

	fmt.Printf("Rendered HTML:\n%s\n", buf.String())
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html Parse, Render, and EscapeString in pkg:golang/golang.org/x/net@v0.55.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.55.0"
  ],
  "symbols": [
    "golang.org/x/net/html.EscapeString",
    "golang.org/x/net/html.Parse",
    "golang.org/x/net/html.Render"
  ]
}

package main

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

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

func main() {
	// Assertion 1: html.EscapeString escapes special characters like ampersands, angle brackets, and quotes for safe HTML insertion
	unescaped := `<div id="test">& 'hello' "world"</div>`
	escaped := html.EscapeString(unescaped)
	expectedEscaped := `&lt;div id=&#34;test&#34;&gt;&amp; &#39;hello&#39; &#34;world&#34;&lt;/div&gt;`
	if escaped != expectedEscaped {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected %q, got %q\n", expectedEscaped, escaped)
		os.Exit(1)
	}

	// Assertion 2: html.Parse parses an HTML document into a DocumentNode tree with correct node hierarchy and attributes
	input := `<!DOCTYPE html><html><head><title>Test Page</title></head><body><div class="box" id="main-box"><p>Sample Text</p></div></body></html>`
	doc, err := html.Parse(strings.NewReader(input))
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: html.Parse error: %v\n", err)
		os.Exit(1)
	}
	if doc == nil || doc.Type != html.DocumentNode {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected DocumentNode, got %v\n", doc)
		os.Exit(1)
	}

	var findFirstByAtom func(*html.Node, atom.Atom) *html.Node
	findFirstByAtom = func(n *html.Node, a atom.Atom) *html.Node {
		if n == nil {
			return nil
		}
		if n.DataAtom == a {
			return n
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			if res := findFirstByAtom(c, a); res != nil {
				return res
			}
		}
		return nil
	}

	divNode := findFirstByAtom(doc, atom.Div)
	if divNode == nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: div element not found\n")
		os.Exit(1)
	}
	var classVal, idVal string
	for _, attr := range divNode.Attr {
		if attr.Key == "class" {
			classVal = attr.Val
		}
		if attr.Key == "id" {
			idVal = attr.Val
		}
	}
	if classVal != "box" || idVal != "main-box" {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected class='box' id='main-box', got class=%q id=%q\n", classVal, idVal)
		os.Exit(1)
	}

	pNode := findFirstByAtom(divNode, atom.P)
	if pNode == nil || pNode.FirstChild == nil || pNode.FirstChild.Type != html.TextNode || pNode.FirstChild.Data != "Sample Text" {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected p text 'Sample Text', got %+v\n", pNode)
		os.Exit(1)
	}

	// Assertion 3: html.Render serializes an HTML node tree back into formatted HTML written to an io.Writer
	var buf bytes.Buffer
	if err := html.Render(&buf, divNode); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: html.Render error: %v\n", err)
		os.Exit(1)
	}
	rendered := buf.String()
	expectedSub := `<div class="box" id="main-box"><p>Sample Text</p></div>`
	if !strings.Contains(rendered, expectedSub) {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: rendered HTML %q does not contain %q\n", rendered, expectedSub)
		os.Exit(1)
	}

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