better comments and error message for unknown out_of_range_mode variable

lib/pagy/extras/out_of_range.rb

@@ -9,20 +9,20 @@ module OutOfRange
  def initialize(vars)
  super
  rescue OutOfRangeError
- @out_of_range = true  # adds the out_of_range flag
+ @out_of_range = true # add the out_of_range flag
  case @vars[:out_of_range_mode]
  when :exception
- raise
+ raise # same as without the extra
  when :last_page
- page = @vars[:page]  # save the very initial page (even after re-run)
- super(vars.merge!(page: @last))  # re-run with the last page
- @vars[:page] = page  # restore the inital page
+ initial_page = @vars[:page] # save the very initial page (even after re-run)
+ super(vars.merge!(page: @last)) # re-run with the last page
+ @vars[:page] = initial_page # restore the inital page
  when :empty_page
- @offset = @items = @from = @to = 0  # vars relative to the actual page
- @prev = @last
- extend(Series)
+ @offset = @items = @from = @to = 0 # vars relative to the actual page
+ @prev = @last # prev relative to the actual page
+ extend(Series) # special series for :empty_page
  else
- raise ArgumentError, "Unknown mode #{@vars[:out_of_range_mode]}"
+ raise ArgumentError, "expected :out_of_range_mode variable in [:last_page, :empty_page, :exception]; got #{@vars[:out_of_range_mode].inspect}"
  end
  end