CSV::Parser#build_scanner

# File tmp/rubies/ruby-3.1.3/lib/csv/parser.rb, line 840
def build_scanner
  inputs = @samples.collect do |sample|
    UnoptimizedStringIO.new(sample)
  end
  if @input.is_a?(StringIO)
    inputs << UnoptimizedStringIO.new(@input.read)
  else
    inputs << @input
  end
  begin
    chunk_size_value = ENV[SCANNER_TEST_CHUNK_SIZE_NAME]
  rescue # Ractor::IsolationError
    # Ractor on Ruby 3.0 can't read ENV value.
    chunk_size_value = SCANNER_TEST_CHUNK_SIZE_VALUE
  end
  chunk_size = Integer((chunk_size_value || "1"), 10)
  InputsScanner.new(inputs,
                    @encoding,
                    @row_separator,
                    chunk_size: chunk_size)
end