golang.org/x/net v0.0.0-20210525063256-abc453219eb5: 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@v0.0.0-20210525063256-abc453219eb5
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5
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:sha256:0cf46a591ae8499c9762cfd8f87a7bec2a29be58c12bcfdad8445cd9e7583efb","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@v0.0.0-20210525063256-abc453219eb5","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5"],"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@v0.0.0-20210525063256-abc453219eb5"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5","symbols":["golang.org/x/net/html.ErrorNode"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.20

require golang.org/x/net v0.0.0-20210525063256-abc453219eb5

golang.org/x/net v0.0.0-20210525063256-abc453219eb5 h1:wjuX4b5yYQnEQHzd+CBcrcC6OVR2J1CN6mUy0oSxIPo=
golang.org/x/net v0.0.0-20210525063256-abc453219eb5/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html.ErrorNode in pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.0.0-20210525063256-abc453219eb5"
  ],
  "symbols": [
    "golang.org/x/net/html.ErrorNode"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// 1. Verify html.ErrorNode equals NodeType(0).
	if html.ErrorNode != html.NodeType(0) {
		fmt.Fprintf(os.Stderr, "expected html.ErrorNode to equal 0, got %v\n", html.ErrorNode)
		os.Exit(1)
	}

	// 2. Verify zero-value html.Node has Type == html.ErrorNode.
	var n html.Node
	if n.Type != html.ErrorNode {
		fmt.Fprintf(os.Stderr, "expected zero-value html.Node.Type == html.ErrorNode, got %v\n", n.Type)
		os.Exit(1)
	}

	// 3. Verify constructing an html.Node with Type: html.ErrorNode preserves Type and Data.
	sentinel := &html.Node{
		Type: html.ErrorNode,
		Data: "invalid-node",
	}
	if sentinel.Type != html.ErrorNode || sentinel.Data != "invalid-node" {
		fmt.Fprintf(os.Stderr, "unexpected sentinel node state: %+v\n", sentinel)
		os.Exit(1)
	}

	// 4. Verify html.ErrorNode is distinct from standard non-error NodeType values.
	standardTypes := []html.NodeType{
		html.TextNode,
		html.DocumentNode,
		html.ElementNode,
		html.CommentNode,
		html.DoctypeNode,
		html.RawNode,
	}
	for _, st := range standardTypes {
		if st == html.ErrorNode {
			fmt.Fprintf(os.Stderr, "expected NodeType %v to differ from html.ErrorNode\n", st)
			os.Exit(1)
		}
	}

	// 5. Verify html.Parse on valid HTML markup produces no html.ErrorNode in the tree.
	root, err := html.Parse(strings.NewReader("<!DOCTYPE html><html><head><title>t</title></head><body><div>ok</div><!--c--></body></html>"))
	if err != nil {
		fmt.Fprintf(os.Stderr, "html.Parse error: %v\n", err)
		os.Exit(1)
	}
	var checkTree func(*html.Node) int
	checkTree = func(cur *html.Node) int {
		if cur.Type == html.ErrorNode {
			fmt.Fprintf(os.Stderr, "found unexpected html.ErrorNode in parsed tree\n")
			os.Exit(1)
		}
		visited := 1
		for child := cur.FirstChild; child != nil; child = child.NextSibling {
			visited += checkTree(child)
		}
		return visited
	}
	if count := checkTree(root); count < 6 {
		fmt.Fprintf(os.Stderr, "expected at least 6 nodes in parsed tree, got %d\n", count)
		os.Exit(1)
	}
}