golang.org/x/net v0.51.0: html.CommentNode

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.CommentNode in pkg:golang/golang.org/x/net@v0.51.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.51.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/html.CommentNode

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:cc549c50a808e7605d98b00cba5f98c48bffd6f977f653dcd40bc48b8d07e176","contract":["html.CommentNode represents an HTML comment node with its comment text in Node.Data","html.Parse parses HTML comments into nodes of Type html.CommentNode","html.Render serializes an html.CommentNode into HTML comment markup \u003c!-- text --\u003e","html.CommentNode with empty Data serializes into \u003c!----\u003e","html.CommentNode can be programmatically constructed and inserted into an HTML DOM tree","html.ParseFragment parses HTML comment strings into CommentNode children in context"],"goal":"verify golang.org/x/net/html.CommentNode in pkg:golang/golang.org/x/net@v0.51.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.51.0"],"schemaVersion":1,"symbols":["golang.org/x/net/html.CommentNode"]},"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@v0.51.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.51.0","symbols":["golang.org/x/net/html.CommentNode"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.25.0

require golang.org/x/net v0.51.0

golang.org/x/net v0.51.0 h1:94R/GTO7mt3/4wIKpcR5gkGmRLOuE/2hNGeWq/GBIFo=
golang.org/x/net v0.51.0/go.mod h1:aamm+2QF5ogm02fjy5Bb7CQ0WMt1/WVM7FtyaTLlA9Y=

package main

import (
	"bytes"
	"fmt"
	"strings"

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

func main() {
	rawHTML := "<div><!-- greeting --><span>Hello World</span></div>"
	doc, err := html.Parse(strings.NewReader(rawHTML))
	if err != nil {
		panic(err)
	}

	commentNode := &html.Node{
		Type: html.CommentNode,
		Data: " appended comment ",
	}
	doc.AppendChild(commentNode)

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

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

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html.CommentNode in pkg:golang/golang.org/x/net@v0.51.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.51.0"
  ],
  "symbols": [
    "golang.org/x/net/html.CommentNode"
  ]
}

package main

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

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

func findComments(n *html.Node) []*html.Node {
	var comments []*html.Node
	var walk func(*html.Node)
	walk = func(curr *html.Node) {
		if curr.Type == html.CommentNode {
			comments = append(comments, curr)
		}
		for c := curr.FirstChild; c != nil; c = c.NextSibling {
			walk(c)
		}
	}
	walk(n)
	return comments
}

func main() {
	// 1. html.CommentNode represents an HTML comment node with its comment text in Node.Data
	manualNode := &html.Node{
		Type: html.CommentNode,
		Data: "manual-comment-text",
	}
	if manualNode.Type != html.CommentNode {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected CommentNode type, got %v\n", manualNode.Type)
		os.Exit(1)
	}
	if manualNode.Data != "manual-comment-text" {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected 'manual-comment-text', got %q\n", manualNode.Data)
		os.Exit(1)
	}

	// 2. html.Parse parses HTML comments into nodes of Type html.CommentNode
	htmlDoc := `<!DOCTYPE html><html><body><!-- first comment --><div>text</div><!-- second comment --></body></html>`
	doc, err := html.Parse(strings.NewReader(htmlDoc))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: html.Parse returned error: %v\n", err)
		os.Exit(1)
	}
	comments := findComments(doc)
	if len(comments) != 2 {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected 2 comment nodes, got %d\n", len(comments))
		os.Exit(1)
	}
	if comments[0].Data != " first comment " {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected ' first comment ', got %q\n", comments[0].Data)
		os.Exit(1)
	}
	if comments[1].Data != " second comment " {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected ' second comment ', got %q\n", comments[1].Data)
		os.Exit(1)
	}

	// 3. html.Render serializes an html.CommentNode into HTML comment markup <!-- text -->
	var buf3 bytes.Buffer
	renderNode := &html.Node{
		Type: html.CommentNode,
		Data: " rendered text ",
	}
	if err := html.Render(&buf3, renderNode); err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: html.Render error: %v\n", err)
		os.Exit(1)
	}
	expectedRender := "<!-- rendered text -->"
	if buf3.String() != expectedRender {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected %q, got %q\n", expectedRender, buf3.String())
		os.Exit(1)
	}

	// 4. html.CommentNode with empty Data serializes into <!---->
	var buf4 bytes.Buffer
	emptyComment := &html.Node{
		Type: html.CommentNode,
		Data: "",
	}
	if err := html.Render(&buf4, emptyComment); err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: html.Render empty error: %v\n", err)
		os.Exit(1)
	}
	if buf4.String() != "<!---->" {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected '<!---->', got %q\n", buf4.String())
		os.Exit(1)
	}

	// 5. html.CommentNode can be programmatically constructed and inserted into an HTML DOM tree
	parsedTree, err := html.Parse(strings.NewReader("<div><span>Hello</span></div>"))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: html.Parse error: %v\n", err)
		os.Exit(1)
	}
	var span *html.Node
	var findSpan func(*html.Node)
	findSpan = func(curr *html.Node) {
		if curr.Type == html.ElementNode && curr.Data == "span" {
			span = curr
			return
		}
		for c := curr.FirstChild; c != nil; c = c.NextSibling {
			findSpan(c)
		}
	}
	findSpan(parsedTree)
	if span == nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: span element not found\n")
		os.Exit(1)
	}
	insertedComment := &html.Node{
		Type: html.CommentNode,
		Data: " inserted between ",
	}
	span.Parent.InsertBefore(insertedComment, span)

	var buf5 bytes.Buffer
	if err := html.Render(&buf5, parsedTree); err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: html.Render tree error: %v\n", err)
		os.Exit(1)
	}
	if !strings.Contains(buf5.String(), "<!-- inserted between --><span>Hello</span>") {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: rendered HTML does not contain inserted comment: %q\n", buf5.String())
		os.Exit(1)
	}

	// 6. html.ParseFragment parses HTML comment strings into CommentNode children in context
	contextDoc, err := html.Parse(strings.NewReader("<div></div>"))
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: context parse error: %v\n", err)
		os.Exit(1)
	}
	var divContext *html.Node
	var findDiv func(*html.Node)
	findDiv = func(curr *html.Node) {
		if curr.Type == html.ElementNode && curr.Data == "div" {
			divContext = curr
			return
		}
		for c := curr.FirstChild; c != nil; c = c.NextSibling {
			findDiv(c)
		}
	}
	findDiv(contextDoc)
	if divContext == nil {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: context div not found\n")
		os.Exit(1)
	}

	fragmentNodes, err := html.ParseFragment(strings.NewReader("<!-- fragment comment --><b>bold</b>"), divContext)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: ParseFragment error: %v\n", err)
		os.Exit(1)
	}
	if len(fragmentNodes) != 2 {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: expected 2 fragment nodes, got %d\n", len(fragmentNodes))
		os.Exit(1)
	}
	if fragmentNodes[0].Type != html.CommentNode || fragmentNodes[0].Data != " fragment comment " {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: fragment node 0 mismatch: type %v, data %q\n", fragmentNodes[0].Type, fragmentNodes[0].Data)
		os.Exit(1)
	}

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