golang.org/x/net v0.0.0-20191119073136-fc4aabc6c914: html.ErrorToken

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.ErrorToken in pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914
Demonstrate these symbols/APIs:
  - golang.org/x/net/html.ErrorToken

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:a7928a49af8192e2afc9b0f19a40bb61b900b4124e1308fcebf1c1e356ab06f0","contract":["html.ErrorToken equals the zero-value html.TokenType(0) and html.ErrorToken.String() returns \"Error\"","Tokenizer.Next returns html.ErrorToken immediately on empty input with Tokenizer.Err returning io.EOF","Tokenizer.Token returns an html.Token with Type html.ErrorToken and empty String() after reaching ErrorToken","Tokenizer.Next returns html.ErrorToken at end of valid HTML input and continues returning html.ErrorToken on subsequent calls","Tokenizer.Next returns html.ErrorToken and preserves the underlying io.Reader error accessible via Tokenizer.Err","Tokenizer.Next returns html.ErrorToken with html.ErrBufferExceeded when a token exceeds the Tokenizer.SetMaxBuf limit"],"goal":"verify golang.org/x/net/html.ErrorToken in pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914"],"schemaVersion":1,"symbols":["golang.org/x/net/html.ErrorToken"]},"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@v0.0.0-20191119073136-fc4aabc6c914"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914","symbols":["golang.org/x/net/html.ErrorToken"],"verifierAdapter":"golang@1"}

module sample

go 1.21

require golang.org/x/net v0.0.0-20191119073136-fc4aabc6c914

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/net v0.0.0-20191119073136-fc4aabc6c914 h1:MlY3mEfbnWGmUi4rtHOtNnnnN4UJRGSyLPx+DXA5Sq4=
golang.org/x/net v0.0.0-20191119073136-fc4aabc6c914/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.ErrorToken in pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.0.0-20191119073136-fc4aabc6c914"
  ],
  "symbols": [
    "golang.org/x/net/html.ErrorToken"
  ]
}

package main

import (
	"errors"
	"fmt"
	"io"
	"os"
	"strings"

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

type errReader struct {
	err error
}

func (r *errReader) Read(_ []byte) (int, error) {
	return 0, r.err
}

func check(ok bool, desc string) {
	if !ok {
		fmt.Fprintln(os.Stderr, "contract failure:", desc)
		os.Exit(1)
	}
}

func main() {
	// Verify ErrorToken constant identity and String() output
	check(html.ErrorToken == html.TokenType(0), "html.ErrorToken must equal zero-value html.TokenType(0)")
	check(html.ErrorToken.String() == "Error", "html.ErrorToken.String() must return \"Error\"")

	// Verify Tokenizer.Next on empty stream returns ErrorToken and io.EOF
	emptyTokenizer := html.NewTokenizer(strings.NewReader(""))
	check(emptyTokenizer.Err() == nil, "Tokenizer.Err() must be nil before scanning")
	check(emptyTokenizer.Next() == html.ErrorToken, "Tokenizer.Next() on empty input must return html.ErrorToken")
	check(emptyTokenizer.Err() == io.EOF, "Tokenizer.Err() at end of empty stream must be io.EOF")
	emptyToken := emptyTokenizer.Token()
	check(emptyToken.Type == html.ErrorToken, "Tokenizer.Token().Type must be html.ErrorToken after reaching EOF")
	check(emptyToken.String() == "", "Token.String() for ErrorToken must be empty string")

	// Verify Tokenizer.Next after valid HTML tokens returns ErrorToken at EOF and stays at ErrorToken
	htmlTokenizer := html.NewTokenizer(strings.NewReader("<span>text</span>"))
	check(htmlTokenizer.Next() == html.StartTagToken, "first token must be StartTagToken")
	check(htmlTokenizer.Next() == html.TextToken, "second token must be TextToken")
	check(htmlTokenizer.Next() == html.EndTagToken, "third token must be EndTagToken")
	check(htmlTokenizer.Next() == html.ErrorToken, "token after end of HTML stream must be html.ErrorToken")
	check(htmlTokenizer.Err() == io.EOF, "Tokenizer.Err() at end of HTML stream must be io.EOF")
	check(htmlTokenizer.Next() == html.ErrorToken, "subsequent Tokenizer.Next() calls must continue returning html.ErrorToken")

	// Verify Tokenizer.Next propagates custom io.Reader error and returns ErrorToken
	readErr := errors.New("custom reader error")
	failTokenizer := html.NewTokenizer(&errReader{err: readErr})
	check(failTokenizer.Next() == html.ErrorToken, "Tokenizer.Next() on failing reader must return html.ErrorToken")
	check(failTokenizer.Err() == readErr, "Tokenizer.Err() must return underlying io.Reader error")

	// Verify Tokenizer.Next returns ErrorToken with ErrBufferExceeded when SetMaxBuf is exceeded
	limitedTokenizer := html.NewTokenizer(strings.NewReader("<a href=\"https://example.com/long-attribute\">link</a>"))
	limitedTokenizer.SetMaxBuf(10)
	check(limitedTokenizer.Next() == html.ErrorToken, "Tokenizer.Next() must return html.ErrorToken when buffer limit is exceeded")
	check(limitedTokenizer.Err() == html.ErrBufferExceeded, "Tokenizer.Err() must be html.ErrBufferExceeded when SetMaxBuf limit is exceeded")
}