Class: Ast::Merge::YamlFrontmatterDetector

Inherits:
RegionDetectorBase show all
Defined in:
lib/ast/merge/yaml_frontmatter_detector.rb

Overview

Detects YAML frontmatter at the beginning of a document.

YAML frontmatter is delimited by ‘—` at the start and end, and must begin on the first line of the document (optionally preceded by a UTF-8 BOM).

Examples:

YAML frontmatter

---
title: My Document
author: Jane Doe
---

Usage

detector = YamlFrontmatterDetector.new
regions = detector.detect_all(markdown_source)
# => [#<Region type=:yaml_frontmatter content="title: My Document\n...">]

Constant Summary collapse

FRONTMATTER_PATTERN =

Pattern for detecting YAML frontmatter.

  • Must start at beginning of document (or after BOM)

  • Opening delimiter is ‘—` followed by optional whitespace and newline

  • Content is captured (non-greedy)

  • Closing delimiter is ‘—` at start of line, followed by optional whitespace and newline/EOF

/\A(?:\xEF\xBB\xBF)?(---[ \t]*\r?\n)(.*?)(^---[ \t]*(?:\r?\n|\z))/m

Instance Method Summary collapse

Methods inherited from RegionDetectorBase

#inspect, #name, #strip_delimiters?

Instance Method Details

#detect_all(source) ⇒ Array<Region>

Detects YAML frontmatter at the beginning of the document.

Parameters:

  • source (String) —

    the source document to scan

Returns:

  • (Array<Region>) —

    array containing at most one Region for frontmatter



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# File 'lib/ast/merge/yaml_frontmatter_detector.rb', line 46

def detect_all(source)
  return [] if source.nil? || source.empty?

  match = source.match(FRONTMATTER_PATTERN)
  return [] unless match

  opening_delimiter = match[1]
  content = match[2]
  closing_delimiter = match[3]

  # Calculate line numbers
  # Frontmatter starts at line 1 (or after BOM)
  start_line = 1
  # Count newlines in content to determine end line
  # Opening delimiter ends at line 1
  # Content spans from line 2 to line 2 + content_lines - 1
  # Closing delimiter is on the next line
  content_newlines = content.count("\n")
  # end_line is the line with the closing ---
  end_line = start_line + 1 + content_newlines

  # Adjust if content ends without newline
  end_line - 1 if content.end_with?("\n") && content_newlines > 0

  # Actually, let's calculate more carefully
  # Line 1: ---
  # Line 2 to N: content
  # Line N+1: ---
  if content.empty?
    0
  else
    content.count("\n") + (content.end_with?("\n") ? 0 : 1)
  end

  # Simplify: count total newlines in the full match to determine end line
  full_match = match[0]
  total_newlines = full_match.count("\n")
  end_line = total_newlines + (full_match.end_with?("\n") ? 0 : 1)

  [
    Region.new(
      type: region_type,
      content: content,
      start_line: start_line,
      end_line: end_line,
      delimiters: [opening_delimiter.strip, closing_delimiter.strip],
      metadata: {format: :yaml},
    ),
  ]
end

#region_type ⇒ Symbol

Returns the type identifier for YAML frontmatter regions.

Returns:

  • (Symbol) —

    the type identifier for YAML frontmatter regions



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# File 'lib/ast/merge/yaml_frontmatter_detector.rb', line 36

def region_type
  :yaml_frontmatter
end