golang.org/x/net v0.42.0: html.DoctypeNode

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.DoctypeNode in pkg:golang/golang.org/x/net@v0.42.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.42.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/html.DoctypeNode

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:sha256:08aa626428d58cd9c2f58b7a7f4a7605b9a1340ccf2bfe7bd68438940f859b32","contract":["html.DoctypeNode is a NodeType constant","html.DoctypeNode is distinct from other NodeType values","html.Parse parses DOCTYPE declaration as an html.DoctypeNode","html.Parse extracts system and public attributes on html.DoctypeNode","html.Render outputs valid DOCTYPE markup for an html.DoctypeNode"],"goal":"verify golang.org/x/net/html.DoctypeNode in pkg:golang/golang.org/x/net@v0.42.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.42.0"],"schemaVersion":1,"symbols":["golang.org/x/net/html.DoctypeNode"]},"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@v0.42.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.42.0","symbols":["golang.org/x/net/html.DoctypeNode"],"verifierAdapter":"golang@1"}

package sample

import (
	"bytes"

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

// FindDoctype traverses the direct children of the given document node
// and returns the first node with Type == html.DoctypeNode, or nil if none is found.
func FindDoctype(doc *html.Node) *html.Node {
	if doc == nil {
		return nil
	}
	for c := doc.FirstChild; c != nil; c = c.NextSibling {
		if c.Type == html.DoctypeNode {
			return c
		}
	}
	return nil
}

// IsDoctype returns true if the node is non-nil and its Type is html.DoctypeNode.
func IsDoctype(n *html.Node) bool {
	return n != nil && n.Type == html.DoctypeNode
}

// NewDoctype constructs a new html.Node representing a DOCTYPE declaration.
func NewDoctype(name, publicID, systemID string) *html.Node {
	n := &html.Node{
		Type: html.DoctypeNode,
		Data: name,
	}
	if publicID != "" {
		n.Attr = append(n.Attr, html.Attribute{Key: "public", Val: publicID})
	}
	if systemID != "" {
		n.Attr = append(n.Attr, html.Attribute{Key: "system", Val: systemID})
	}
	return n
}

// RenderDoctype serializes a DoctypeNode into its HTML string representation.
func RenderDoctype(n *html.Node) (string, error) {
	var buf bytes.Buffer
	if err := html.Render(&buf, n); err != nil {
		return "", err
	}
	return buf.String(), nil
}

module sample

go 1.26.6

require golang.org/x/net v0.42.0

golang.org/x/net v0.42.0 h1:jzkYrhi3YQWD6MLBJcsklgQsoAcw89EcZbJw8Z614hs=
golang.org/x/net v0.42.0/go.mod h1:FF1RA5d3u7nAYA4z2TkclSCKh68eSXtiFwcWQpPXdt8=

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html.DoctypeNode in pkg:golang/golang.org/x/net@v0.42.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.42.0"
  ],
  "symbols": [
    "golang.org/x/net/html.DoctypeNode"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// Assertion 1: html.DoctypeNode is a NodeType constant
	var nodeType html.NodeType = html.DoctypeNode
	if nodeType != html.DoctypeNode {
		fmt.Fprintf(os.Stderr, "expected nodeType to match html.DoctypeNode\n")
		os.Exit(1)
	}

	// Assertion 2: html.DoctypeNode is distinct from other NodeType values
	if html.DoctypeNode == html.ErrorNode ||
		html.DoctypeNode == html.TextNode ||
		html.DoctypeNode == html.DocumentNode ||
		html.DoctypeNode == html.ElementNode ||
		html.DoctypeNode == html.CommentNode ||
		html.DoctypeNode == html.RawNode {
		fmt.Fprintf(os.Stderr, "expected html.DoctypeNode to be distinct from other NodeType values\n")
		os.Exit(1)
	}

	// Assertion 3: html.Parse parses DOCTYPE declaration as an html.DoctypeNode
	htmlDoc := "<!DOCTYPE html><html><head></head><body><p>Hello</p></body></html>"
	doc, err := html.Parse(strings.NewReader(htmlDoc))
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse HTML: %v\n", err)
		os.Exit(1)
	}
	if doc.Type != html.DocumentNode {
		fmt.Fprintf(os.Stderr, "expected root node to be DocumentNode, got %v\n", doc.Type)
		os.Exit(1)
	}

	dtNode := sample.FindDoctype(doc)
	if dtNode == nil {
		fmt.Fprintf(os.Stderr, "expected doctype node not found\n")
		os.Exit(1)
	}
	if dtNode.Type != html.DoctypeNode {
		fmt.Fprintf(os.Stderr, "expected doctype node to have Type html.DoctypeNode, got %v\n", dtNode.Type)
		os.Exit(1)
	}
	if dtNode.Data != "html" {
		fmt.Fprintf(os.Stderr, "expected doctype node data to be 'html', got %q\n", dtNode.Data)
		os.Exit(1)
	}
	if !sample.IsDoctype(dtNode) {
		fmt.Fprintf(os.Stderr, "expected sample.IsDoctype to return true\n")
		os.Exit(1)
	}

	// Assertion 4: html.Parse extracts system and public attributes on html.DoctypeNode
	htmlWithSystem := `<!DOCTYPE html SYSTEM "about:legacy-compat"><html><body></body></html>`
	docWithSystem, err := html.Parse(strings.NewReader(htmlWithSystem))
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse HTML with system doctype: %v\n", err)
		os.Exit(1)
	}
	dtSystem := sample.FindDoctype(docWithSystem)
	if dtSystem == nil || dtSystem.Type != html.DoctypeNode {
		fmt.Fprintf(os.Stderr, "expected DoctypeNode in docWithSystem\n")
		os.Exit(1)
	}
	foundSystem := false
	for _, attr := range dtSystem.Attr {
		if attr.Key == "system" && attr.Val == "about:legacy-compat" {
			foundSystem = true
		}
	}
	if !foundSystem {
		fmt.Fprintf(os.Stderr, "expected system attribute on DoctypeNode\n")
		os.Exit(1)
	}

	// Assertion 5: html.Render outputs valid DOCTYPE markup for an html.DoctypeNode
	manualDoctype := sample.NewDoctype("html", "", "")
	rendered, err := sample.RenderDoctype(manualDoctype)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to render DoctypeNode: %v\n", err)
		os.Exit(1)
	}
	if rendered != "<!DOCTYPE html>" {
		fmt.Fprintf(os.Stderr, "expected '<!DOCTYPE html>', got %q\n", rendered)
		os.Exit(1)
	}

	manualWithSystem := sample.NewDoctype("html", "", "about:legacy-compat")
	renderedSystem, err := sample.RenderDoctype(manualWithSystem)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to render DoctypeNode with system: %v\n", err)
		os.Exit(1)
	}
	if renderedSystem != `<!DOCTYPE html SYSTEM "about:legacy-compat">` {
		fmt.Fprintf(os.Stderr, "expected '<!DOCTYPE html SYSTEM \"about:legacy-compat\">', got %q\n", renderedSystem)
		os.Exit(1)
	}

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