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

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.SelfClosingTagToken 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.SelfClosingTagToken

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:e582dd6c08125afb14eccc01b8cba2405663fec598c1b261ec104e2b61ad0a33","contract":["SelfClosingTagToken is a TokenType constant with value 4 representing self-closing tags","SelfClosingTagToken String method returns string representation \"SelfClosingTag\"","SelfClosingTagToken is distinct from StartTagToken and EndTagToken","Tokenizer Next returns SelfClosingTagToken for void element with self-closing slash syntax","Tokenizer Next returns StartTagToken rather than SelfClosingTagToken for void element without slash","Tokenizer Token returns a Token with Type SelfClosingTagToken, tag Data, and parsed Attributes","Tokenizer TagName and TagAttr extract name and attributes from SelfClosingTagToken","Token with Type SelfClosingTagToken renders as XML-style self-closing tag via String"],"goal":"verify golang.org/x/net/html.SelfClosingTagToken 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.SelfClosingTagToken"]},"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.SelfClosingTagToken"],"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 (
	"fmt"
	"io"
	"strings"

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

func main() {
	htmlContent := `<div class="container"><img src="photo.jpg" alt="preview"/><br/><input type="checkbox" checked/></div>`
	z := html.NewTokenizer(strings.NewReader(htmlContent))

	fmt.Println("Tokenizing HTML with self-closing tags:")
	for {
		tt := z.Next()
		if tt == html.ErrorToken {
			if z.Err() == io.EOF {
				break
			}
			fmt.Printf("Tokenization error: %v\n", z.Err())
			break
		}

		tok := z.Token()
		if tt == html.SelfClosingTagToken {
			fmt.Printf("Found SelfClosingTagToken [%s]: %s (tag: %s, attrs: %d)\n",
				tt.String(), tok.String(), tok.Data, len(tok.Attr))
		}
	}
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html.SelfClosingTagToken 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.SelfClosingTagToken"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// 1. SelfClosingTagToken is a TokenType constant with value 4 representing self-closing tags
	if html.SelfClosingTagToken != 4 {
		fmt.Fprintf(os.Stderr, "Expected SelfClosingTagToken to have value 4, got %d\n", html.SelfClosingTagToken)
		os.Exit(1)
	}

	// 2. SelfClosingTagToken String method returns string representation "SelfClosingTag"
	if html.SelfClosingTagToken.String() != "SelfClosingTag" {
		fmt.Fprintf(os.Stderr, "Expected SelfClosingTagToken.String() to be %q, got %q\n", "SelfClosingTag", html.SelfClosingTagToken.String())
		os.Exit(1)
	}

	// 3. SelfClosingTagToken is distinct from StartTagToken and EndTagToken
	if html.SelfClosingTagToken == html.StartTagToken || html.SelfClosingTagToken == html.EndTagToken {
		fmt.Fprintf(os.Stderr, "Expected SelfClosingTagToken to be distinct from StartTagToken and EndTagToken\n")
		os.Exit(1)
	}

	// 4. Tokenizer Next returns SelfClosingTagToken for void element with self-closing slash syntax
	zSlash := html.NewTokenizer(strings.NewReader(`<img src="photo.jpg" alt="test"/>`))
	ttSlash := zSlash.Next()
	if ttSlash != html.SelfClosingTagToken {
		fmt.Fprintf(os.Stderr, "Expected SelfClosingTagToken for <img .../>, got %v\n", ttSlash)
		os.Exit(1)
	}

	// 5. Tokenizer Next returns StartTagToken rather than SelfClosingTagToken for void element without slash
	zNoSlash := html.NewTokenizer(strings.NewReader(`<img src="photo.jpg">`))
	ttNoSlash := zNoSlash.Next()
	if ttNoSlash != html.StartTagToken {
		fmt.Fprintf(os.Stderr, "Expected StartTagToken for <img> without slash, got %v\n", ttNoSlash)
		os.Exit(1)
	}

	// 6. Tokenizer Token returns a Token with Type SelfClosingTagToken, tag Data, and parsed Attributes
	tok := zSlash.Token()
	if tok.Type != html.SelfClosingTagToken {
		fmt.Fprintf(os.Stderr, "Expected tok.Type to be SelfClosingTagToken, got %v\n", tok.Type)
		os.Exit(1)
	}
	if tok.Data != "img" || tok.DataAtom != atom.Img {
		fmt.Fprintf(os.Stderr, "Expected Data='img' and DataAtom=atom.Img, got Data=%q DataAtom=%v\n", tok.Data, tok.DataAtom)
		os.Exit(1)
	}
	if len(tok.Attr) != 2 || tok.Attr[0].Key != "src" || tok.Attr[0].Val != "photo.jpg" {
		fmt.Fprintf(os.Stderr, "Unexpected attributes: %+v\n", tok.Attr)
		os.Exit(1)
	}

	// 7. Tokenizer TagName and TagAttr extract name and attributes from SelfClosingTagToken
	zStream := html.NewTokenizer(strings.NewReader(`<input type="text" name="user"/>`))
	if tt := zStream.Next(); tt != html.SelfClosingTagToken {
		fmt.Fprintf(os.Stderr, "Expected SelfClosingTagToken for input tag, got %v\n", tt)
		os.Exit(1)
	}
	name, hasAttr := zStream.TagName()
	if string(name) != "input" || !hasAttr {
		fmt.Fprintf(os.Stderr, "Expected TagName 'input' with hasAttr=true, got %q, %v\n", string(name), hasAttr)
		os.Exit(1)
	}
	k1, v1, more1 := zStream.TagAttr()
	if string(k1) != "type" || string(v1) != "text" || !more1 {
		fmt.Fprintf(os.Stderr, "Expected first attr type=text more=true, got %s=%s more=%v\n", k1, v1, more1)
		os.Exit(1)
	}
	k2, v2, more2 := zStream.TagAttr()
	if string(k2) != "name" || string(v2) != "user" || more2 {
		fmt.Fprintf(os.Stderr, "Expected second attr name=user more=false, got %s=%s more=%v\n", k2, v2, more2)
		os.Exit(1)
	}

	// 8. Token with Type SelfClosingTagToken renders as XML-style self-closing tag via String
	rendered := tok.String()
	if rendered != `<img src="photo.jpg" alt="test"/>` {
		fmt.Fprintf(os.Stderr, "Expected rendered self closing tag %q, got %q\n", `<img src="photo.jpg" alt="test"/>`, rendered)
		os.Exit(1)
	}

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