golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7: 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@v0.0.0-20190813141303-74dc4d7220e7
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.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:e04490f18cd2da1b75dbe2bdef2a4c5101babfdd30b495619584d031a6b15be2","contract":["html.ParseFragment with nil context parses a fragment into a root html element containing head and body","html.ParseFragment with a body element context parses child elements directly without outer html/body wrappers","html.ParseFragment with a table element context wraps tr elements inside an implicit tbody element","html.ParseFragment with a select element context parses option elements and preserves their attributes"],"goal":"verify golang.org/x/net/html.ParseFragment 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.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@v0.0.0-20190813141303-74dc4d7220e7"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.0.0-20190813141303-74dc4d7220e7","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 from an io.Reader using the provided context node.
func ParseFragment(r io.Reader, context *html.Node) ([]*html.Node, error) {
	return html.ParseFragment(r, context)
}

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

// FindFirstElement traverses the node slice depth-first and returns the first element matching tag.
func FindFirstElement(nodes []*html.Node, tag string) *html.Node {
	for _, n := range nodes {
		if found := findElement(n, tag); found != nil {
			return found
		}
	}
	return nil
}

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

// GetAttr looks up an attribute value on an html.Node.
func GetAttr(n *html.Node, key string) (string, bool) {
	if n == nil {
		return "", false
	}
	for _, a := range n.Attr {
		if a.Key == key {
			return a.Val, true
		}
	}
	return "", false
}

module sample

go 1.21

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.ParseFragment 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.ParseFragment"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// 1. ParseFragment with nil context returns a root html element containing head and body
	nodes1, err := sample.ParseFragmentString("<p>Hello Fragment</p>", nil)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: unexpected 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 single html element root\n")
		os.Exit(1)
	}
	if sample.FindFirstElement(nodes1, "head") == nil || sample.FindFirstElement(nodes1, "body") == nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected head and body elements\n")
		os.Exit(1)
	}
	pNode := sample.FindFirstElement(nodes1, "p")
	if pNode == nil || pNode.FirstChild == nil || pNode.FirstChild.Data != "Hello Fragment" {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected p element with text\n")
		os.Exit(1)
	}

	// 2. ParseFragment with a body context parses child elements directly without html/body wrapper
	bodyCtx := &html.Node{
		Type:     html.ElementNode,
		Data:     "body",
		DataAtom: atom.Body,
	}
	nodes2, err := sample.ParseFragmentString("<h1>Title</h1><em>Note</em>", bodyCtx)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: unexpected error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes2) != 2 || nodes2[0].Data != "h1" || nodes2[1].Data != "em" {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected h1 and em top-level nodes\n")
		os.Exit(1)
	}

	// 3. ParseFragment with a table context wraps tr elements inside an implicit tbody element
	tableCtx := &html.Node{
		Type:     html.ElementNode,
		Data:     "table",
		DataAtom: atom.Table,
	}
	nodes3, err := sample.ParseFragmentString("<tr><td>Cell</td></tr>", tableCtx)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: unexpected 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\n")
		os.Exit(1)
	}
	tdNode := sample.FindFirstElement(nodes3, "td")
	if tdNode == nil || tdNode.FirstChild == nil || tdNode.FirstChild.Data != "Cell" {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: expected td element with Cell text\n")
		os.Exit(1)
	}

	// 4. ParseFragment with a select context parses option nodes and preserves attributes
	selectCtx := &html.Node{
		Type:     html.ElementNode,
		Data:     "select",
		DataAtom: atom.Select,
	}
	nodes4, err := sample.ParseFragment(strings.NewReader(`<option value="a">Alpha</option><option value="b" selected>Beta</option>`), selectCtx)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: unexpected error: %v\n", err)
		os.Exit(1)
	}
	if len(nodes4) != 2 || nodes4[0].Data != "option" || nodes4[1].Data != "option" {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected 2 option nodes\n")
		os.Exit(1)
	}
	valA, okA := sample.GetAttr(nodes4[0], "value")
	_, okSelected := sample.GetAttr(nodes4[1], "selected")
	if !okA || valA != "a" || !okSelected {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: option attributes not preserved\n")
		os.Exit(1)
	}
}