SeleniumHQ/selenium · error · ArgumentError

Custom page size must include :width and :height

Error message

Custom page size must include :width and :height

What it means

When page_size= is given a Hash, it must contain both :width and :height keys (Symbol keys). If either is missing, ArgumentError is raised. The values represent dimensions in centimeters.

Source

Thrown at rb/lib/selenium/webdriver/common/print_options.rb:83

      # Sets the page size. Can be a predefined symbol or custom size hash.
      #
      # @param [Symbol, Hash] value The predefined size (:letter, :legal, :a4, :tabloid) or a custom hash.
      def page_size=(value)
        predefined_sizes = {
          letter: {width: 21.59, height: 27.94},
          legal: {width: 21.59, height: 35.56},
          a4: {width: 21.0, height: 29.7},
          tabloid: {width: 27.94, height: 43.18}
        }

        case value
        when Symbol
          raise ArgumentError, "Invalid page size: #{value}" unless predefined_sizes.key?(value)

          @page_size = predefined_sizes[value]
        when Hash
          unless value.key?(:width) && value.key?(:height)
            raise ArgumentError, 'Custom page size must include :width and :height'
          end

          @page_size = value
        else
          raise ArgumentError, 'Page size must be a Symbol or a Hash'
        end
      end
    end
  end
end

View on GitHub (pinned to aa36b38e69)

Solutions

1. Include both Symbol keys: page_size = { width: 21.0, height: 29.7 }.
2. If keys come from JSON/string sources, transform them: hash.transform_keys(&:to_sym).
3. Validate value.key?(:width) && value.key?(:height) before assignment.

Example fix

# before
print_options.page_size = { 'width' => 21.0 }

# after
print_options.page_size = { width: 21.0, height: 29.7 }

raise ArgumentError, 'page size needs :width and :height' unless hash.key?(:width) && hash.key?(:height)

def complete_page_hash?(hash)
  hash.is_a?(Hash) && hash.key?(:width) && hash.key?(:height)
end

begin
  print_options.page_size = hash
rescue ArgumentError => e
  raise unless e.message.include?('width and :height')
  print_options.page_size = hash.transform_keys(&:to_sym)
end

When it happens

Trigger: Passing { width: 21.0 } without :height. Using string keys 'width'/'height' instead of Symbols. Passing an incomplete hash built from partial user input.

Common situations: Constructing the hash programmatically and omitting one dimension. Using string keys because the data came from JSON. Copying a partial config.

Related errors

• Invalid page size: #{value}
• Page size must be a Symbol or a Hash
• Value of scale should be between 0.1 and 2
• Orientation value must be one of {self.ORIENTATION_VALUES}
• {property_name} cannot be less than 0

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/cde7b4971e81a747. Report an issue: GitHub.