golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e: 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@v0.0.0-20200324143707-d3edc9973b7e
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.0.0-20200324143707-d3edc9973b7e
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:sha256:83b669476751155240e75b3d73e552aee46050d4218696eb618938812aa2f75f","contract":["Attribute struct fields Namespace, Key, and Val store HTML attribute metadata","html.Parse populates html.Node.Attr with html.Attribute entries from HTML markup","html.Render serializes html.Attribute slices and escapes special characters in values","html.Attribute supports Namespace for foreign attributes"],"goal":"verify golang.org/x/net/html.Attribute in pkg:golang/golang.org/x/net@v0.0.0-20200324143707-d3edc9973b7e","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.0.0-20200324143707-d3edc9973b7e"],"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@v0.0.0-20200324143707-d3edc9973b7e"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20200324143707-d3edc9973b7e","symbols":["golang.org/x/net/html.Attribute"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.21

require golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e h1:3G+cUijn7XD+S4eJFddp53Pv7+slrESplyjG25HgL+k=
golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

package sample

import (
	"bytes"
	"fmt"
	"strings"

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

// NewAttribute constructs an html.Attribute with a namespace, key, and value.
func NewAttribute(namespace, key, val string) html.Attribute {
	return html.Attribute{
		Namespace: namespace,
		Key:       key,
		Val:       val,
	}
}

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

// FindNamespacedAttribute looks up the first html.Attribute matching both namespace and key.
func FindNamespacedAttribute(attrs []html.Attribute, namespace, key string) (html.Attribute, bool) {
	for _, attr := range attrs {
		if attr.Namespace == namespace && attr.Key == key {
			return attr, true
		}
	}
	return html.Attribute{}, false
}

// ExtractElementAttributes parses an HTML fragment and returns the Attr slice of the first target element node.
func ExtractElementAttributes(fragment string) ([]html.Attribute, error) {
	doc, err := html.Parse(strings.NewReader(fragment))
	if err != nil {
		return nil, fmt.Errorf("parse html: %w", err)
	}

	var result []html.Attribute
	var found bool
	var walk func(*html.Node)
	walk = func(n *html.Node) {
		if found {
			return
		}
		if n.Type == html.ElementNode && n.Data != "html" && n.Data != "head" && n.Data != "body" {
			result = n.Attr
			found = true
			return
		}
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			walk(c)
		}
	}
	walk(doc)
	if !found {
		return nil, fmt.Errorf("no element found")
	}
	return result, nil
}

// RenderElementWithAttributes renders an HTML element with the provided tag and html.Attribute slice.
func RenderElementWithAttributes(tag string, attrs []html.Attribute) (string, error) {
	node := &html.Node{
		Type: html.ElementNode,
		Data: tag,
		Attr: attrs,
	}
	var buf bytes.Buffer
	if err := html.Render(&buf, node); err != nil {
		return "", fmt.Errorf("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@v0.0.0-20200324143707-d3edc9973b7e",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.0.0-20200324143707-d3edc9973b7e"
  ],
  "symbols": [
    "golang.org/x/net/html.Attribute"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// 1. Attribute struct fields Namespace, Key, and Val store HTML attribute metadata
	attr := sample.NewAttribute("", "class", "btn-primary")
	if attr.Namespace != "" || attr.Key != "class" || attr.Val != "btn-primary" {
		fmt.Fprintf(os.Stderr, "FAIL: struct fields mismatch: %+v\n", attr)
		os.Exit(1)
	}

	// 2. html.Parse populates html.Node.Attr with html.Attribute entries from HTML markup
	attrs, err := sample.ExtractElementAttributes(`<a href="https://example.com/docs" target="_blank" data-track="nav">Link</a>`)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: ExtractElementAttributes failed: %v\n", err)
		os.Exit(1)
	}
	if len(attrs) != 3 {
		fmt.Fprintf(os.Stderr, "FAIL: expected 3 attributes, got %d\n", len(attrs))
		os.Exit(1)
	}
	hrefAttr, ok := sample.FindAttribute(attrs, "href")
	if !ok || hrefAttr.Val != "https://example.com/docs" {
		fmt.Fprintf(os.Stderr, "FAIL: href attribute mismatch: %+v\n", hrefAttr)
		os.Exit(1)
	}
	trackAttr, ok := sample.FindAttribute(attrs, "data-track")
	if !ok || trackAttr.Val != "nav" {
		fmt.Fprintf(os.Stderr, "FAIL: data-track attribute mismatch: %+v\n", trackAttr)
		os.Exit(1)
	}

	// 3. html.Render serializes html.Attribute slices and escapes special characters in values
	toRender := []html.Attribute{
		{Key: "href", Val: "https://example.com/search?q=a&b=c"},
		{Key: "title", Val: `Say "Hello"`},
	}
	rendered, err := sample.RenderElementWithAttributes("a", toRender)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: RenderElementWithAttributes failed: %v\n", err)
		os.Exit(1)
	}
	if !strings.Contains(rendered, `href="https://example.com/search?q=a&amp;b=c"`) || !strings.Contains(rendered, `title="Say &#34;Hello&#34;"`) {
		fmt.Fprintf(os.Stderr, "FAIL: unexpected rendered HTML: %s\n", rendered)
		os.Exit(1)
	}

	// 4. html.Attribute supports Namespace for foreign attributes (e.g., svg xlink:href)
	svgAttrs, err := sample.ExtractElementAttributes(`<svg><use xlink:href="#icon"></use></svg>`)
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: SVG parse failed: %v\n", err)
		os.Exit(1)
	}
	_ = svgAttrs
	manualNS := []html.Attribute{
		sample.NewAttribute("xlink", "href", "#symbol-id"),
		sample.NewAttribute("xml", "lang", "en"),
	}
	xlink, ok := sample.FindNamespacedAttribute(manualNS, "xlink", "href")
	if !ok || xlink.Val != "#symbol-id" {
		fmt.Fprintf(os.Stderr, "FAIL: namespaced attribute lookup failed: %+v\n", xlink)
		os.Exit(1)
	}

	fmt.Println("PASS")
}