golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e: html.ErrorNode

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.ErrorNode 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.ErrorNode

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:db0871517f96ac499cf8ab061a81961bbb0fc24b0e869e24287fc2a84339ecf1","contract":["html.ErrorNode is a NodeType constant equal to uint32(0)","zero-value html.Node struct has Type equal to html.ErrorNode by default","explicitly constructed html.Node with html.ErrorNode retains its Type and Data","html.ErrorNode is distinct from TextNode, DocumentNode, ElementNode, CommentNode, DoctypeNode, and RawNode","html.Parse on valid HTML produces a DOM tree containing no html.ErrorNode nodes"],"goal":"verify golang.org/x/net/html.ErrorNode 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.ErrorNode"]},"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.ErrorNode"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.20

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=

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

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// 1. html.ErrorNode is the zero-value NodeType constant (uint32(0)).
	if html.ErrorNode != html.NodeType(0) {
		fmt.Fprintf(os.Stderr, "expected html.ErrorNode == 0, got %v\n", html.ErrorNode)
		os.Exit(1)
	}

	// 2. A zero-initialized html.Node defaults to Type == html.ErrorNode.
	var zeroNode html.Node
	if zeroNode.Type != html.ErrorNode {
		fmt.Fprintf(os.Stderr, "expected zero html.Node.Type == html.ErrorNode, got %v\n", zeroNode.Type)
		os.Exit(1)
	}

	// 3. An explicitly constructed html.Node with Type: html.ErrorNode retains its Type and Data.
	errNode := &html.Node{
		Type: html.ErrorNode,
		Data: "parse error sentinel",
	}
	if errNode.Type != html.ErrorNode || errNode.Data != "parse error sentinel" {
		fmt.Fprintf(os.Stderr, "unexpected errNode state: %+v\n", errNode)
		os.Exit(1)
	}

	// 4. html.ErrorNode is distinct from all other standard NodeType constants.
	otherTypes := []html.NodeType{
		html.TextNode,
		html.DocumentNode,
		html.ElementNode,
		html.CommentNode,
		html.DoctypeNode,
		html.RawNode,
	}
	for _, nt := range otherTypes {
		if nt == html.ErrorNode {
			fmt.Fprintf(os.Stderr, "expected NodeType %v to be distinct from html.ErrorNode\n", nt)
			os.Exit(1)
		}
	}

	// 5. Parsing valid HTML via html.Parse produces a DOM tree without any html.ErrorNode nodes.
	doc, err := html.Parse(strings.NewReader("<!DOCTYPE html><html><body><p>hello</p><!--comment--></body></html>"))
	if err != nil {
		fmt.Fprintf(os.Stderr, "html.Parse failed: %v\n", err)
		os.Exit(1)
	}
	var walk func(*html.Node) int
	walk = func(n *html.Node) int {
		if n.Type == html.ErrorNode {
			fmt.Fprintf(os.Stderr, "unexpected ErrorNode in parsed valid HTML tree\n")
			os.Exit(1)
		}
		count := 1
		for c := n.FirstChild; c != nil; c = c.NextSibling {
			count += walk(c)
		}
		return count
	}
	if total := walk(doc); total < 5 {
		fmt.Fprintf(os.Stderr, "expected at least 5 nodes in parsed tree, got %d\n", total)
		os.Exit(1)
	}
}