golang.org/x/net v0.61.0: html.UnescapeString

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.UnescapeString in pkg:golang/golang.org/x/net@v0.61.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.61.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/html.UnescapeString

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:sha256:7276a015fb1e350786d5bd542d4b745586e7828d85a5474b7ce1ed3664adc43f","contract":["html.UnescapeString correctly unescapes HTML entity names, numeric character references, and hexadecimal character references"],"goal":"verify golang.org/x/net/html.UnescapeString in pkg:golang/golang.org/x/net@v0.61.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.61.0"],"schemaVersion":1,"symbols":["golang.org/x/net/html.UnescapeString"]},"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@v0.61.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.61.0","symbols":["golang.org/x/net/html.UnescapeString"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.0

require golang.org/x/net v0.61.0

golang.org/x/net v0.61.0 h1:RR+6j/BTBCrggOLugxa+66R8FvoN6MHlzDlZIbN9YFw=
golang.org/x/net v0.61.0/go.mod h1:WgDCOTH8iwtB66T4/GfI94AHo/hhdb7Hah9NDseQfiI=

package main

import (
	"fmt"

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

func main() {
	escaped := `<div class="content">'Hello & Welcome'</div>`
	unescaped := html.UnescapeString(escaped)
	fmt.Printf("Escaped:   %s\n", escaped)
	fmt.Printf("Unescaped: %s\n", unescaped)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/html.UnescapeString in pkg:golang/golang.org/x/net@v0.61.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.61.0"
  ],
  "symbols": [
    "golang.org/x/net/html.UnescapeString"
  ]
}

package main

import (
	"fmt"
	"os"

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

func main() {
	// Assertion: html.UnescapeString correctly unescapes HTML entity names, numeric character references, and hexadecimal character references
	tests := []struct {
		input    string
		expected string
	}{
		{"", ""},
		{"Hello, World!", "Hello, World!"},
		{"&lt;div&gt;", "<div>"},
		{"&quot;hello&#39;s&quot;", "\"hello's\""},
		{"&amp; &lt; &gt; &quot; &apos;", "& < > \" '"},
		{"&#65;&#66;&#67;", "ABC"},
		{"&#x41;&#x42;&#x43;", "ABC"},
		{"&copy; 2026", "© 2026"},
		{"&euro; &#8364; &#x20AC;", "€ € €"},
	}

	for _, tc := range tests {
		got := html.UnescapeString(tc.input)
		if got != tc.expected {
			fmt.Fprintf(os.Stderr, "html.UnescapeString(%q) = %q; expected %q\n", tc.input, got, tc.expected)
			os.Exit(1)
		}
	}

	// Round-trip check with html.EscapeString
	raw := `<span class="quote">"Fish & Chips" <'special'></span>`
	escaped := html.EscapeString(raw)
	unescaped := html.UnescapeString(escaped)
	if unescaped != raw {
		fmt.Fprintf(os.Stderr, "round-trip failed: expected %q, got %q\n", raw, unescaped)
		os.Exit(1)
	}

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