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

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.WithRenderer 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.WithRenderer

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:b06abb316ebe6ae315143c9b9c7b666a2044ab5548b097b8f495351fc6dfd124","contract":["WithRenderer returns a non-nil Option function","WithRenderer with custom HTMLRenderer configures heading ID prefix, absolute prefix and link attributes","WithRenderer with custom PlainTextRenderer outputs document header, body text and footer","WithRenderer with UpperTextRenderer intercepts and transforms AST text nodes to uppercase","WithRenderer overrides default rendering behavior in blackfriday.Run"],"goal":"verify github.com/russross/blackfriday/v2.WithRenderer 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.WithRenderer"]},"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.WithRenderer"],"verifierAdapter":"golang@1"}

module sample

go 1.22

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 sample

import (
	"io"
	"strings"

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

// NewCustomHTMLRenderer constructs an HTMLRenderer with custom parameters.
func NewCustomHTMLRenderer(headingPrefix string, absPrefix string, flags blackfriday.HTMLFlags) *blackfriday.HTMLRenderer {
	params := blackfriday.HTMLRendererParameters{
		HeadingIDPrefix: headingPrefix,
		AbsolutePrefix:  absPrefix,
		Flags:           flags,
	}
	return blackfriday.NewHTMLRenderer(params)
}

// RenderWithRenderer renders markdown input using blackfriday.WithRenderer option.
func RenderWithRenderer(input []byte, renderer blackfriday.Renderer, additionalOpts ...blackfriday.Option) []byte {
	opts := append([]blackfriday.Option{blackfriday.WithRenderer(renderer)}, additionalOpts...)
	return blackfriday.Run(input, opts...)
}

// PlainTextRenderer is a custom Renderer implementation that extracts plain text.
type PlainTextRenderer struct{}

// NewPlainTextRenderer creates a new PlainTextRenderer.
func NewPlainTextRenderer() *PlainTextRenderer {
	return &PlainTextRenderer{}
}

// RenderNode renders AST nodes into plain text.
func (r *PlainTextRenderer) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
	switch node.Type {
	case blackfriday.Text:
		w.Write(node.Literal)
	case blackfriday.Code:
		w.Write(node.Literal)
	case blackfriday.CodeBlock:
		if entering {
			w.Write(node.Literal)
			w.Write([]byte("\n"))
		}
	case blackfriday.Paragraph:
		if !entering {
			w.Write([]byte("\n"))
		}
	case blackfriday.Heading:
		if !entering {
			w.Write([]byte("\n"))
		}
	case blackfriday.Item:
		if entering {
			w.Write([]byte("- "))
		}
	}
	return blackfriday.GoToNext
}

// RenderHeader writes header content for PlainTextRenderer.
func (r *PlainTextRenderer) RenderHeader(w io.Writer, ast *blackfriday.Node) {
	io.WriteString(w, "=== DOCUMENT START ===\n")
}

// RenderFooter writes footer content for PlainTextRenderer.
func (r *PlainTextRenderer) RenderFooter(w io.Writer, ast *blackfriday.Node) {
	io.WriteString(w, "=== DOCUMENT END ===\n")
}

// UpperTextRenderer wraps rendering text with uppercase transformation.
type UpperTextRenderer struct {
	html *blackfriday.HTMLRenderer
}

// NewUpperTextRenderer creates a renderer that converts text literals to uppercase.
func NewUpperTextRenderer() *UpperTextRenderer {
	return &UpperTextRenderer{
		html: blackfriday.NewHTMLRenderer(blackfriday.HTMLRendererParameters{}),
	}
}

// RenderNode intercepts text nodes to uppercase them, delegating other nodes.
func (u *UpperTextRenderer) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
	if node.Type == blackfriday.Text {
		upper := strings.ToUpper(string(node.Literal))
		w.Write([]byte(upper))
		return blackfriday.GoToNext
	}
	return u.html.RenderNode(w, node, entering)
}

// RenderHeader delegates header rendering.
func (u *UpperTextRenderer) RenderHeader(w io.Writer, ast *blackfriday.Node) {
	u.html.RenderHeader(w, ast)
}

// RenderFooter delegates footer rendering.
func (u *UpperTextRenderer) RenderFooter(w io.Writer, ast *blackfriday.Node) {
	u.html.RenderFooter(w, ast)
}

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

package main

import (
	"fmt"
	"os"
	"strings"

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

func main() {
	// Assertion 1: WithRenderer returns a non-nil Option function
	opt := blackfriday.WithRenderer(sample.NewPlainTextRenderer())
	if opt == nil {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: WithRenderer returned nil Option\n")
		os.Exit(1)
	}

	// Assertion 2: WithRenderer with custom HTMLRenderer respects HeadingIDPrefix, AbsolutePrefix and HTMLFlags
	customHTML := sample.NewCustomHTMLRenderer("sec-", "https://cdn.example.com", blackfriday.HrefTargetBlank)
	inputHTML := []byte("# Introduction\n\n[Documentation](/guide.html)")
	outHTML := sample.RenderWithRenderer(
		inputHTML,
		customHTML,
		blackfriday.WithExtensions(blackfriday.CommonExtensions|blackfriday.AutoHeadingIDs),
	)
	outHTMLStr := string(outHTML)

	if !strings.Contains(outHTMLStr, `id="sec-introduction"`) {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected heading id prefix 'sec-', got %q\n", outHTMLStr)
		os.Exit(1)
	}
	if !strings.Contains(outHTMLStr, `href="https://cdn.example.com/guide.html"`) {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected absolute prefix 'https://cdn.example.com/guide.html', got %q\n", outHTMLStr)
		os.Exit(1)
	}
	if !strings.Contains(outHTMLStr, `target="_blank"`) {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected target=\"_blank\" on link, got %q\n", outHTMLStr)
		os.Exit(1)
	}

	// Assertion 3: WithRenderer with PlainTextRenderer renders custom header, body text and footer
	plainRenderer := sample.NewPlainTextRenderer()
	inputPlain := []byte("# Title\n\nHello world paragraph.\n\n- item 1\n- item 2")
	outPlain := sample.RenderWithRenderer(inputPlain, plainRenderer)
	outPlainStr := string(outPlain)

	if !strings.HasPrefix(outPlainStr, "=== DOCUMENT START ===\n") {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected header '=== DOCUMENT START ===', got %q\n", outPlainStr)
		os.Exit(1)
	}
	if !strings.HasSuffix(strings.TrimSpace(outPlainStr), "=== DOCUMENT END ===") {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected footer '=== DOCUMENT END ===', got %q\n", outPlainStr)
		os.Exit(1)
	}
	if !strings.Contains(outPlainStr, "Hello world paragraph.") {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected body text, got %q\n", outPlainStr)
		os.Exit(1)
	}
	if !strings.Contains(outPlainStr, "- item 1") || !strings.Contains(outPlainStr, "- item 2") {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected list items, got %q\n", outPlainStr)
		os.Exit(1)
	}

	// Assertion 4: WithRenderer with UpperTextRenderer intercepts and transforms text nodes to uppercase
	upperRenderer := sample.NewUpperTextRenderer()
	inputUpper := []byte("hello blackfriday renderer")
	outUpper := sample.RenderWithRenderer(inputUpper, upperRenderer)
	outUpperStr := string(outUpper)

	if !strings.Contains(outUpperStr, "<p>HELLO BLACKFRIDAY RENDERER</p>") {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected uppercased text in html paragraph, got %q\n", outUpperStr)
		os.Exit(1)
	}

	// Assertion 5: blackfriday.Run with WithRenderer overrides the default renderer behavior
	defaultOut := blackfriday.Run([]byte("# Title"))
	customOut := blackfriday.Run([]byte("# Title"), blackfriday.WithRenderer(sample.NewPlainTextRenderer()))
	if string(defaultOut) == string(customOut) {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: custom renderer should produce different output from default renderer\n")
		os.Exit(1)
	}

	fmt.Println("All blackfriday.WithRenderer contract assertions passed successfully.")
}