golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7: 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@v0.0.0-20190813141303-74dc4d7220e7
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7
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:sha256:8deaeef1f5e39ea36e6704ed0c750cc2474491874b6537228d7765ff40d79337","contract":["html.ErrorNode is a NodeType constant equal to uint32(0)","uninitialized html.Node struct has Type equal to html.ErrorNode by default","explicitly created html.Node with html.ErrorNode retains its Type and Data and is rejected by html.Render with an error","html.ErrorNode is distinct from TextNode, DocumentNode, ElementNode, CommentNode, and DoctypeNode","html.Parse on valid HTML produces a DOM tree where no nodes have Type equal to html.ErrorNode"],"goal":"verify golang.org/x/net/html.ErrorNode in pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7"],"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@v0.0.0-20190813141303-74dc4d7220e7"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7","symbols":["golang.org/x/net/html.ErrorNode"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.20

require golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7 h1:fHDIZ2oxGnUZRN6WgWFCbYBjH9uqVPRCUVUDhs0wnbA=
golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
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@v0.0.0-20190813141303-74dc4d7220e7",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7"
  ],
  "symbols": [
    "golang.org/x/net/html.ErrorNode"
  ]
}

package main

import (
	"bytes"
	"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,
	// and html.Render rejects rendering an ErrorNode with a non-nil error.
	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)
	}
	var buf bytes.Buffer
	if err := html.Render(&buf, errNode); err == nil {
		fmt.Fprintf(os.Stderr, "expected html.Render to fail on html.ErrorNode, got nil\n")
		os.Exit(1)
	}

	// 4. html.ErrorNode is distinct from all other standard NodeType constants in this version.
	otherTypes := []html.NodeType{
		html.TextNode,
		html.DocumentNode,
		html.ElementNode,
		html.CommentNode,
		html.DoctypeNode,
	}
	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)
	}
}