Module: RedQuilt::Frontmatter

Defined in:
lib/red_quilt/frontmatter.rb

Overview

Extracts a leading YAML frontmatter block from a Markdown source.

Class Method Summary collapse

Class Method Details

.blank_out(source, offset) ⇒ Object

Replaces every character before offset with a blank line for each consumed source line, keeping later line numbers intact.



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# File 'lib/red_quilt/frontmatter.rb', line 49

def blank_out(source, offset)
  consumed = source[0, offset]
  ("\n" * consumed.count("\n")) + source[offset..]
end

.extract(source, diagnostics: nil) ⇒ Object

Extracts frontmatter from source, returning a two-element array: [data, body]. data is the parsed Hash (or nil when there is no frontmatter), and body is the source with the frontmatter region blanked out.

diagnostics is an optional array; on a YAML syntax error a warning Diagnostic is appended and data is returned as nil.



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# File 'lib/red_quilt/frontmatter.rb', line 22

def extract(source, diagnostics: nil)
  match = PATTERN.match(source)
  return [nil, source] unless match

  data = parse_yaml(match[1], diagnostics: diagnostics)
  body = blank_out(source, match.end(0))
  [data, body]
end

.parse_yaml(yaml, diagnostics: nil) ⇒ Object

Parses the YAML body with a restricted loader (no arbitrary object instantiation; Date / Time permitted for common frontmatter dates). Returns the parsed value, or nil on a syntax error.



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# File 'lib/red_quilt/frontmatter.rb', line 34

def parse_yaml(yaml, diagnostics: nil)
  Psych.safe_load(yaml, permitted_classes: [Date, Time], aliases: false)
rescue Psych::SyntaxError => e
  diagnostics&.push(
    Diagnostic.new(
      severity: :warning,
      rule: :frontmatter,
      message: "invalid YAML frontmatter: #{e.message}",
    ),
  )
  nil
end