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

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.Document 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.Document
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:4bf05d3a5707a9c939a6f10d692b4db589b0faa108c2906c956650b7d011d5d2","contract":["blackfriday.Document is the root NodeType returned by Parser.Parse representing the markdown document AST","blackfriday.Document root node holds child block elements with parent pointer referencing the Document node","blackfriday.NewNode with Document type creates an empty Document AST node","Node.Walk traverses the AST starting with entering blackfriday.Document and ending with exiting Document","blackfriday.New.Parse on empty markdown returns a Document root node with nil child pointers"],"goal":"verify github.com/russross/blackfriday/v2.Document 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.Document"]},"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.Document"],"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("# Document Root Example\n\nExploring blackfriday AST Document node.")
	parser := blackfriday.New()
	ast := parser.Parse(markdown)

	if ast.Type == blackfriday.Document {
		fmt.Printf("Parsed root AST node type: %s\n", ast.Type.String())
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/russross/blackfriday/v2.Document 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.Document"
  ]
}

package main

import (
	"fmt"
	"os"

	"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 Document contract assertions passed successfully.")
}

func runContract() error {
	// Assertion 1: blackfriday.Document is the root NodeType returned by Parser.Parse representing the markdown document AST
	input := []byte("# Title\n\nFirst paragraph text.")
	doc := blackfriday.New().Parse(input)
	if doc == nil {
		return fmt.Errorf("expected non-nil AST from Parse, got nil")
	}
	if doc.Type != blackfriday.Document {
		return fmt.Errorf("expected root node type blackfriday.Document (%d), got: %d", blackfriday.Document, doc.Type)
	}
	if doc.Type.String() != "Document" {
		return fmt.Errorf("expected doc.Type.String() to be 'Document', got: %q", doc.Type.String())
	}

	// Assertion 2: blackfriday.Document root node holds child block elements with parent pointer referencing the Document node
	if doc.Parent != nil {
		return fmt.Errorf("expected Document root node Parent to be nil, got: %v", doc.Parent)
	}
	if doc.FirstChild == nil || doc.FirstChild.Type != blackfriday.Heading {
		return fmt.Errorf("expected FirstChild to be Heading, got: %v", doc.FirstChild)
	}
	if doc.LastChild == nil || doc.LastChild.Type != blackfriday.Paragraph {
		return fmt.Errorf("expected LastChild to be Paragraph, got: %v", doc.LastChild)
	}
	if doc.FirstChild.Parent != doc || doc.LastChild.Parent != doc {
		return fmt.Errorf("expected child nodes Parent to point to Document root")
	}

	// Assertion 3: blackfriday.NewNode with Document type creates an empty Document AST node
	newNode := blackfriday.NewNode(blackfriday.Document)
	if newNode == nil {
		return fmt.Errorf("expected NewNode(Document) to return non-nil node")
	}
	if newNode.Type != blackfriday.Document {
		return fmt.Errorf("expected newNode.Type to be Document, got: %v", newNode.Type)
	}
	if newNode.FirstChild != nil || newNode.Parent != nil {
		return fmt.Errorf("expected NewNode(Document) to have nil FirstChild and Parent")
	}

	// Assertion 4: Node.Walk traverses the AST starting with entering blackfriday.Document and ending with exiting Document
	var enteredDoc, exitedDoc bool
	var walkOrder []blackfriday.NodeType

	doc.Walk(func(node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
		if node.Type == blackfriday.Document {
			if entering {
				enteredDoc = true
			} else {
				exitedDoc = true
			}
		}
		if entering {
			walkOrder = append(walkOrder, node.Type)
		}
		return blackfriday.GoToNext
	})

	if !enteredDoc || !exitedDoc {
		return fmt.Errorf("expected Document node to be visited on entering and exiting during Walk")
	}
	if len(walkOrder) == 0 || walkOrder[0] != blackfriday.Document {
		return fmt.Errorf("expected first visited node in Walk to be Document, got: %v", walkOrder)
	}

	// Assertion 5: blackfriday.New.Parse on empty markdown returns a Document root node with nil child pointers
	emptyDoc := blackfriday.New().Parse([]byte(""))
	if emptyDoc == nil || emptyDoc.Type != blackfriday.Document {
		return fmt.Errorf("expected Document root node on empty input, got: %v", emptyDoc)
	}
	if emptyDoc.FirstChild != nil {
		return fmt.Errorf("expected empty Document to have nil FirstChild, got: %v", emptyDoc.FirstChild)
	}

	return nil
}