github.com/russross/blackfriday/v2 v2.1.0: AutoHeadingIDs

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 github.com/russross/blackfriday/v2.AutoHeadingIDs in pkg:golang/github.com/russross/blackfriday/v2@v2.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/russross/blackfriday/v2@v2.1.0
Demonstrate these symbols/APIs:
  - github.com/russross/blackfriday/v2.AutoHeadingIDs

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:sha256:8bf38969e3690a3efaf40e2ef4e063423ca1607a5fb1874b94786d5c413a6584","contract":["blackfriday.AutoHeadingIDs enables automatic slug-based HTML heading ID attribute generation","blackfriday.AutoHeadingIDs with custom HTMLRenderer HeadingIDPrefix prefixes generated heading IDs","blackfriday.New with AutoHeadingIDs populates HeadingData.HeadingID on AST Heading nodes","blackfriday.AutoHeadingIDs sanitizes special characters and spaces into URL-safe kebab-case heading IDs"],"goal":"verify github.com/russross/blackfriday/v2.AutoHeadingIDs in pkg:golang/github.com/russross/blackfriday/v2@v2.1.0","kind":"HOW","packages":["pkg:golang/github.com/russross/blackfriday/v2@v2.1.0"],"schemaVersion":1,"symbols":["github.com/russross/blackfriday/v2.AutoHeadingIDs"]},"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/github.com/russross/blackfriday/v2@v2.1.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/russross/blackfriday/v2@v2.1.0","symbols":["github.com/russross/blackfriday/v2.AutoHeadingIDs"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/russross/blackfriday/v2 v2.1.0

github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=

package main

import (
	"fmt"

	"github.com/russross/blackfriday/v2"
)

func main() {
	markdown := []byte("# Getting Started\n\nThis heading receives an auto-generated HTML anchor ID.")
	html := blackfriday.Run(markdown, blackfriday.WithExtensions(blackfriday.AutoHeadingIDs))
	fmt.Printf("Rendered HTML:\n%s\n", string(html))
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/russross/blackfriday/v2.AutoHeadingIDs in pkg:golang/github.com/russross/blackfriday/v2@v2.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/russross/blackfriday/v2@v2.1.0"
  ],
  "symbols": [
    "github.com/russross/blackfriday/v2.AutoHeadingIDs"
  ]
}

package main

import (
	"fmt"
	"os"
	"strings"

	"github.com/russross/blackfriday/v2"
)

func main() {
	if err := runContract(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract verification failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All AutoHeadingIDs contract assertions passed successfully.")
}

func runContract() error {
	// Assertion 1: AutoHeadingIDs generates automatic slug-based HTML heading ID attribute
	inputBasic := []byte("# User Guide Overview\n\nContent paragraph.")
	outputBasic := blackfriday.Run(inputBasic, blackfriday.WithExtensions(blackfriday.AutoHeadingIDs))
	expectedHeading := `<h1 id="user-guide-overview">User Guide Overview</h1>`
	if !strings.Contains(string(outputBasic), expectedHeading) {
		return fmt.Errorf("expected %q in AutoHeadingIDs output, got: %s", expectedHeading, string(outputBasic))
	}

	// Assertion 2: AutoHeadingIDs with custom HTMLRenderer HeadingIDPrefix prefixes generated heading IDs
	params := blackfriday.HTMLRendererParameters{
		HeadingIDPrefix: "doc-section-",
		Flags:           blackfriday.CommonHTMLFlags,
	}
	renderer := blackfriday.NewHTMLRenderer(params)
	outputPrefixed := blackfriday.Run(
		[]byte("## Configuration Settings"),
		blackfriday.WithRenderer(renderer),
		blackfriday.WithExtensions(blackfriday.AutoHeadingIDs),
	)
	expectedPrefixed := `<h2 id="doc-section-configuration-settings">Configuration Settings</h2>`
	if !strings.Contains(string(outputPrefixed), expectedPrefixed) {
		return fmt.Errorf("expected %q with HeadingIDPrefix, got: %s", expectedPrefixed, string(outputPrefixed))
	}

	// Assertion 3: blackfriday.New with AutoHeadingIDs populates HeadingData.HeadingID on AST Heading nodes
	parser := blackfriday.New(blackfriday.WithExtensions(blackfriday.AutoHeadingIDs))
	ast := parser.Parse([]byte("# Architecture & API Design\n\nBody text."))
	if ast == nil || ast.Type != blackfriday.Document {
		return fmt.Errorf("expected Document AST root node, got: %v", ast)
	}
	headingNode := ast.FirstChild
	if headingNode == nil || headingNode.Type != blackfriday.Heading {
		return fmt.Errorf("expected Heading AST node, got: %v", headingNode)
	}
	if headingNode.HeadingData.HeadingID != "architecture-api-design" {
		return fmt.Errorf("expected HeadingID 'architecture-api-design', got %q", headingNode.HeadingData.HeadingID)
	}

	// Assertion 4: AutoHeadingIDs sanitizes special characters and spaces into URL-safe kebab-case heading IDs
	inputSpecial := []byte("### Quick-Start & Feature 100% (Beta)!")
	outputSpecial := blackfriday.Run(inputSpecial, blackfriday.WithExtensions(blackfriday.AutoHeadingIDs))
	expectedSpecial := `<h3 id="quick-start-feature-100-beta">Quick-Start &amp; Feature 100% (Beta)!</h3>`
	if !strings.Contains(string(outputSpecial), expectedSpecial) {
		return fmt.Errorf("expected %q for special characters, got: %s", expectedSpecial, string(outputSpecial))
	}

	return nil
}