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

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.ParseFragment 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.ParseFragment

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:fce9ad77ab9f6c961772a63a78ea86ed0d1bb4e9e1082936a80267ae1a357cbd","contract":["html.ParseFragment parses HTML fragment without context into a root html element containing head and body","html.ParseFragment parses child elements directly when provided an element context like body","html.ParseFragment wraps table rows in an implicit tbody when parsed with a table context","html.ParseFragment parses option elements and preserves attributes when given a select context","html.ParseFragment handles malformed fragment markup by performing HTML5 error recovery without failing"],"goal":"verify golang.org/x/net/html.ParseFragment 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.ParseFragment"]},"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.ParseFragment"],"verifierAdapter":"golang@1"}

package sample

import (
	"io"
	"strings"

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

// ParseFragment parses an HTML fragment with the given context element.
// If context is nil, it parses within the default context.
func ParseFragment(r io.Reader, context *html.Node) ([]*html.Node, error) {
	return html.ParseFragment(r, context)
}

// ParseFragmentString parses an HTML string fragment with the given context element.
func ParseFragmentString(fragment string, context *html.Node) ([]*html.Node, error) {
	return html.ParseFragment(strings.NewReader(fragment), context)
}

// FindFirstElement searches depth-first for the first element node with the specified tag name.
func FindFirstElement(nodes []*html.Node, tagName string) *html.Node {
	for _, n := range nodes {
		if found := findInTree(n, tagName); found != nil {
			return found
		}
	}
	return nil
}

func findInTree(n *html.Node, tagName string) *html.Node {
	if n == nil {
		return nil
	}
	if n.Type == html.ElementNode && n.Data == tagName {
		return n
	}
	for c := n.FirstChild; c != nil; c = c.NextSibling {
		if found := findInTree(c, tagName); found != nil {
			return found
		}
	}
	return nil
}

// GetAttr returns the value of the attribute with the given key, and whether it was found.
func GetAttr(n *html.Node, key string) (string, bool) {
	if n == nil {
		return "", false
	}
	for _, attr := range n.Attr {
		if attr.Key == key {
			return attr.Val, true
		}
	}
	return "", false
}

module sample

go 1.26.6

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=

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

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// Assertion 1: html.ParseFragment parses HTML fragment without context into a root html element containing head and body
	nodes1, err := sample.ParseFragmentString("<p>Paragraph</p>", nil)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: parse error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes1) != 1 || nodes1[0].Type != html.ElementNode || nodes1[0].Data != "html" {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected 1 root html node, got %v\n", nodes1)
		os.Exit(1)
	}
	headNode := sample.FindFirstElement(nodes1, "head")
	bodyNode := sample.FindFirstElement(nodes1, "body")
	pNode := sample.FindFirstElement(nodes1, "p")
	if headNode == nil || bodyNode == nil || pNode == nil {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: missing head, body, or p element\n")
		os.Exit(1)
	}
	if pNode.FirstChild == nil || pNode.FirstChild.Data != "Paragraph" {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: p content mismatch\n")
		os.Exit(1)
	}

	// Assertion 2: html.ParseFragment parses child elements directly when provided an element context like body
	bodyContext := &html.Node{
		Type:     html.ElementNode,
		Data:     "body",
		DataAtom: atom.Body,
	}
	nodes2, err := sample.ParseFragmentString("<h2>Heading</h2><span>Details</span>", bodyContext)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: parse error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes2) != 2 {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected 2 top-level nodes, got %d\n", len(nodes2))
		os.Exit(1)
	}
	if nodes2[0].Data != "h2" || nodes2[1].Data != "span" {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: unexpected tags %q, %q\n", nodes2[0].Data, nodes2[1].Data)
		os.Exit(1)
	}
	if nodes2[0].FirstChild == nil || nodes2[0].FirstChild.Data != "Heading" ||
		nodes2[1].FirstChild == nil || nodes2[1].FirstChild.Data != "Details" {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: inner text mismatch\n")
		os.Exit(1)
	}

	// Assertion 3: html.ParseFragment wraps table rows in an implicit tbody when parsed with a table context
	tableContext := &html.Node{
		Type:     html.ElementNode,
		Data:     "table",
		DataAtom: atom.Table,
	}
	nodes3, err := sample.ParseFragmentString("<tr><td>RowItem</td></tr>", tableContext)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: parse error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes3) != 1 || nodes3[0].Data != "tbody" {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected implicit tbody root, got %v\n", nodes3)
		os.Exit(1)
	}
	trNode := sample.FindFirstElement(nodes3, "tr")
	tdNode := sample.FindFirstElement(nodes3, "td")
	if trNode == nil || tdNode == nil {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected tr and td nodes within tbody\n")
		os.Exit(1)
	}
	if tdNode.FirstChild == nil || tdNode.FirstChild.Data != "RowItem" {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: td text mismatch\n")
		os.Exit(1)
	}

	// Assertion 4: html.ParseFragment parses option elements and preserves attributes when given a select context
	selectContext := &html.Node{
		Type:     html.ElementNode,
		Data:     "select",
		DataAtom: atom.Select,
	}
	optsHTML := `<option value="first">First Choice</option><option value="second" selected>Second Choice</option>`
	nodes4, err := sample.ParseFragmentString(optsHTML, selectContext)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: parse error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes4) != 2 {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected 2 option nodes, got %d\n", len(nodes4))
		os.Exit(1)
	}
	val1, ok1 := sample.GetAttr(nodes4[0], "value")
	if !ok1 || val1 != "first" {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: option 1 value mismatch: %q (found: %v)\n", val1, ok1)
		os.Exit(1)
	}
	val2, ok2 := sample.GetAttr(nodes4[1], "value")
	if !ok2 || val2 != "second" {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: option 2 value mismatch: %q (found: %v)\n", val2, ok2)
		os.Exit(1)
	}
	_, hasSelected := sample.GetAttr(nodes4[1], "selected")
	if !hasSelected {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: option 2 missing selected attribute\n")
		os.Exit(1)
	}

	// Assertion 5: html.ParseFragment handles malformed fragment markup by performing HTML5 error recovery without failing
	malformedHTML := `<div><p>Unclosed paragraph<span>Unclosed span</div>`
	nodes5, err := sample.ParseFragment(strings.NewReader(malformedHTML), nil)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: expected graceful parse of malformed fragment, got error: %v\n", err)
		os.Exit(1)
	}
	divNode := sample.FindFirstElement(nodes5, "div")
	if divNode == nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: expected div element to be recovered\n")
		os.Exit(1)
	}
	pRecovered := sample.FindFirstElement([]*html.Node{divNode}, "p")
	spanRecovered := sample.FindFirstElement([]*html.Node{divNode}, "span")
	if pRecovered == nil || spanRecovered == nil {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: expected child p and span elements to be recovered\n")
		os.Exit(1)
	}

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