SeleniumHQ/selenium · error · TypeError

#{source.type} is not a valid input type

Error message

#{source.type} is not a valid input type

What it means

Raised as TypeError by Scroll#assert_source when the source passed to Scroll.new(source:, ...) is not a WheelInput. Scroll encodes a W3C wheel scroll action and is only valid on a wheel input source. Reached via WheelInput#create_scroll (which passes self) or by direct construction.

Source

Thrown at rb/lib/selenium/webdriver/common/interactions/scroll.rb:44

      # @api private
      #

      class Scroll < Interaction
        def initialize(source:, origin: :viewport, duration: 0.25, **opts)
          super(source)
          @type = :scroll
          @duration = duration * 1000
          @origin = origin
          @x_offset = opts.delete(:x) || 0
          @y_offset = opts.delete(:y) || 0
          @delta_x = opts.delete(:delta_x) || 0
          @delta_y = opts.delete(:delta_y) || 0

          raise ArgumentError, "Invalid arguments: #{opts.keys}" unless opts.empty?
        end

        def assert_source(source)
          raise TypeError, "#{source.type} is not a valid input type" unless source.is_a? WheelInput
        end

        def encode
          {'type' => type.to_s,
           'duration' => @duration.to_i,
           'x' => @x_offset,
           'y' => @y_offset,
           'deltaX' => @delta_x,
           'deltaY' => @delta_y,
           'origin' => @origin.is_a?(Element) ? @origin : @origin.to_s}
        end
      end # PointerPress
    end # Interactions
  end # WebDriver
end # Selenium

View on GitHub (pinned to aa36b38e69)

Solutions

1. Use the public scroll DSL (driver.action.scroll_by / scroll_to / scroll_from) which obtains a WheelInput internally via wheel_input.
2. If constructing Scroll directly, ensure source.is_a?(Selenium::WebDriver::Interactions::WheelInput).

Example fix

# before
scroll = Selenium::WebDriver::Interactions::Scroll.new(source: pointer, delta_y: 200) # => TypeError

# after
wheel = Selenium::WebDriver::Interactions::WheelInput.new
wheel.create_scroll(delta_x: 0, delta_y: 200)

def wheel_input?(src)
  src.is_a?(Selenium::WebDriver::Interactions::WheelInput)
end

Scroll.new(source: src, **opts) if wheel_input?(src)

When it happens

Trigger: Constructing Interactions::Scroll.new(source: pointer, ...) or source: key_input with a non-wheel device. Reached through the public DSL only if the internal wheel_input lookup is bypassed by custom code.

Common situations: Custom action-builder code that aliases the wrong device; refactors that reuse a pointer/key device variable for scrolling.

Related errors

• #{source.type} is not a valid input type
• #{source.type} is not a valid input type
• #{source.type} is not a valid input type
• #{source.type} is not a valid input type
• #{source.type} is not a valid input type

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/5a86092969cadefb. Report an issue: GitHub.