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

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.Attribute 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.Attribute

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:f21c5664be942ae35f8224284c269aa7be17be698ce81031dbbf4c11a92f0f7a","contract":["Attribute struct holds Namespace, Key, and Val fields representing HTML element attributes","html.Parse extracts element attributes into html.Node.Attr as a slice of html.Attribute","html.Render serializes html.Node with html.Attribute slice into valid HTML attribute syntax","Attribute supports namespaced attributes such as xml and xlink","Attribute values preserve exact strings including whitespace, URLs, and custom data attributes"],"goal":"verify golang.org/x/net/html.Attribute 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.Attribute"]},"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.Attribute"],"verifierAdapter":"golang@1"}

module sample

go 1.26.0

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 sample

import (
	"bytes"
	"fmt"
	"strings"

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

// FindAttribute searches an attribute slice for the first attribute matching the given key (with empty namespace).
func FindAttribute(attrs []html.Attribute, key string) (html.Attribute, bool) {
	for _, a := range attrs {
		if a.Namespace == "" && a.Key == key {
			return a, true
		}
	}
	return html.Attribute{}, false
}

// FindNamespacedAttribute searches an attribute slice for an attribute matching the given namespace and key.
func FindNamespacedAttribute(attrs []html.Attribute, namespace, key string) (html.Attribute, bool) {
	for _, a := range attrs {
		if a.Namespace == namespace && a.Key == key {
			return a, true
		}
	}
	return html.Attribute{}, false
}

// SetOrAddAttribute updates an existing attribute with the matching key or appends a new one.
func SetOrAddAttribute(attrs []html.Attribute, key, val string) []html.Attribute {
	for i, a := range attrs {
		if a.Namespace == "" && a.Key == key {
			attrs[i].Val = val
			return attrs
		}
	}
	return append(attrs, html.Attribute{Key: key, Val: val})
}

// ExtractFirstElementAttributes parses an HTML string and returns the attributes of the first element found.
func ExtractFirstElementAttributes(htmlStr string) ([]html.Attribute, error) {
	doc, err := html.Parse(strings.NewReader(htmlStr))
	if err != nil {
		return nil, fmt.Errorf("failed to parse HTML: %w", err)
	}

	var firstElemAttrs []html.Attribute
	var found bool
	var traverse func(*html.Node)
	traverse = func(n *html.Node) {
		if found {
			return
		}
		if n.Type == html.ElementNode && n.Data != "html" && n.Data != "head" && n.Data != "body" {
			firstElemAttrs = n.Attr
			found = true
			return
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			traverse(c)
		}
	}
	traverse(doc)

	if !found {
		return nil, fmt.Errorf("no element node found in HTML")
	}
	return firstElemAttrs, nil
}

// RenderElementWithAttributes builds and renders an HTML element node with given tag, attributes, and text content.
func RenderElementWithAttributes(tag string, attrs []html.Attribute, textContent string) (string, error) {
	node := &html.Node{
		Type: html.ElementNode,
		Data: tag,
		Attr: attrs,
	}
	if textContent != "" {
		node.AppendChild(&html.Node{
			Type: html.TextNode,
			Data: textContent,
		})
	}

	var buf bytes.Buffer
	if err := html.Render(&buf, node); err != nil {
		return "", fmt.Errorf("failed to render HTML: %w", err)
	}
	return buf.String(), nil
}

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

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// Assertion 1: Attribute struct holds Namespace, Key, and Val fields representing HTML element attributes
	attr1 := html.Attribute{
		Namespace: "",
		Key:       "class",
		Val:       "btn primary",
	}
	if attr1.Key != "class" || attr1.Val != "btn primary" || attr1.Namespace != "" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 1 failed: incorrect Attribute struct fields\n")
		os.Exit(1)
	}

	// Assertion 2: html.Parse extracts element attributes into html.Node.Attr as a slice of html.Attribute
	htmlInput := `<div id="container" class="main-box" data-custom="xyz">Hello</div>`
	attrs, err := sample.ExtractFirstElementAttributes(htmlInput)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 2 failed to extract attributes: %v\n", err)
		os.Exit(1)
	}
	if len(attrs) != 3 {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 2 failed: expected 3 attributes, got %d\n", len(attrs))
		os.Exit(1)
	}
	idAttr, foundId := sample.FindAttribute(attrs, "id")
	if !foundId || idAttr.Val != "container" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 2 failed: id attribute mismatch: %+v\n", idAttr)
		os.Exit(1)
	}
	classAttr, foundClass := sample.FindAttribute(attrs, "class")
	if !foundClass || classAttr.Val != "main-box" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 2 failed: class attribute mismatch: %+v\n", classAttr)
		os.Exit(1)
	}
	dataAttr, foundData := sample.FindAttribute(attrs, "data-custom")
	if !foundData || dataAttr.Val != "xyz" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 2 failed: data-custom attribute mismatch: %+v\n", dataAttr)
		os.Exit(1)
	}

	// Assertion 3: html.Render serializes html.Node with html.Attribute slice into valid HTML attribute syntax
	renderAttrs := []html.Attribute{
		{Key: "href", Val: "https://example.com/path?q=1&v=2"},
		{Key: "target", Val: "_blank"},
	}
	rendered, err := sample.RenderElementWithAttributes("a", renderAttrs, "Link Text")
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 3 failed to render: %v\n", err)
		os.Exit(1)
	}
	if !strings.Contains(rendered, `href="https://example.com/path?q=1&amp;v=2"`) || !strings.Contains(rendered, `target="_blank"`) {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 3 failed: rendered HTML mismatch: %s\n", rendered)
		os.Exit(1)
	}

	// Assertion 4: Attribute supports namespaced attributes such as xml and xlink
	nsAttrs := []html.Attribute{
		{Namespace: "xlink", Key: "href", Val: "#icon-star"},
		{Namespace: "xml", Key: "lang", Val: "en-US"},
	}
	xlinkAttr, foundXlink := sample.FindNamespacedAttribute(nsAttrs, "xlink", "href")
	if !foundXlink || xlinkAttr.Val != "#icon-star" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 4 failed: namespaced xlink:href not found or incorrect\n")
		os.Exit(1)
	}
	xmlAttr, foundXml := sample.FindNamespacedAttribute(nsAttrs, "xml", "lang")
	if !foundXml || xmlAttr.Val != "en-US" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 4 failed: namespaced xml:lang not found or incorrect\n")
		os.Exit(1)
	}

	// Assertion 5: Attribute values preserve exact strings including whitespace, URLs, and custom data attributes
	updatedAttrs := sample.SetOrAddAttribute(attrs, "class", "main-box updated")
	updatedAttrs = sample.SetOrAddAttribute(updatedAttrs, "data-version", "v0.51.0")
	updatedClass, foundUpdatedClass := sample.FindAttribute(updatedAttrs, "class")
	if !foundUpdatedClass || updatedClass.Val != "main-box updated" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 5 failed: updated class value mismatch\n")
		os.Exit(1)
	}
	newAttr, foundNewAttr := sample.FindAttribute(updatedAttrs, "data-version")
	if !foundNewAttr || newAttr.Val != "v0.51.0" {
		fmt.Fprintf(os.Stderr, "FAIL: Assertion 5 failed: new data-version attribute mismatch\n")
		os.Exit(1)
	}

	fmt.Println("PASS: all golang.org/x/net/html.Attribute contract assertions passed")
}