class RuboCop::Cop::ParenthesesCorrector

This autocorrects parentheses

def add_heredoc_comma(corrector, node)

Add a comma back after the heredoc identifier 
def add_heredoc_comma(corrector, node)
  return unless heredoc?(node)
  corrector.insert_after(node.child_nodes.last, ',')
end

def correct(corrector, node) 

def correct(corrector, node)
  corrector.remove(node.loc.begin)
  corrector.remove(node.loc.end)
  handle_orphaned_comma(corrector, node)
  return unless ternary_condition?(node) && next_char_is_question_mark?(node)
  corrector.insert_after(node.loc.end, ' ')
end

def extend_range_for_heredoc(node, range)

It'll be added back in the right place later
If the node contains a heredoc, remove the comma too 
def extend_range_for_heredoc(node, range)
  return range unless heredoc?(node)
  comma_line = range_by_whole_lines(node.loc.end, buffer: node.source_range.source_buffer)
  offset = comma_line.source.match(COMMA_REGEXP)[0]&.size || 0
  range.adjust(end_pos: offset)
end

def handle_orphaned_comma(corrector, node)

preceding it to prevent a syntax error.
If removing parentheses leaves a comma on its own line, remove all the whitespace 
def handle_orphaned_comma(corrector, node)
  return unless only_closing_paren_before_comma?(node)
  range = extend_range_for_heredoc(node, parens_range(node))
  corrector.remove(range)
  add_heredoc_comma(corrector, node)
end

def heredoc?(node) 

def heredoc?(node)
  node.child_nodes.last.loc.is_a?(Parser::Source::Map::Heredoc)
end

def next_char_is_question_mark?(node) 

def next_char_is_question_mark?(node)
  node.loc.last_column == node.parent.loc.question.column
end

def only_closing_paren_before_comma?(node) 

def only_closing_paren_before_comma?(node)
  source_buffer = node.source_range.source_buffer
  line_range = source_buffer.line_range(node.loc.end.line)
  line_range.source.start_with?(/\s*\)\s*,/)
end

def parens_range(node)

Get a range for the closing parenthesis and all whitespace to the left of it 
def parens_range(node)
  range_with_surrounding_space(
    range: node.loc.end,
    buffer: node.source_range.source_buffer,
    side: :left,
    newlines: true,
    whitespace: true,
    continuations: true
  )
end

def ternary_condition?(node) 

def ternary_condition?(node)
  node.parent&.if_type? && node.parent.ternary?
end