Partial payments for shipments in Spree 1.1.0 - only for credit card payments and shipping is applied only to the first shipment.

payment_and_shipment_decorator.rb

module Spree
  Payment.class_eval do
    def complete_or_partial_capture!(amount)
      return false if amount <= 0 || self.state != 'pending'
      # if it's close to total payment, round up or down to total payment
      # this is to counteract rounding errors from tax calculations
      amount = self.amount if ((amount-0.02)..(amount+0.02)).include?(self.amount)
      # check to make sure there is enough money authorized for this payment
      return false if amount > self.amount
      if amount < self.amount # split the payment
        new_payment = self.dup
        new_payment.amount = self.amount - amount
        new_payment.save
        self.update_attribute(:amount, amount)
      end
      if Rails.env.production?
        self.capture!
      else
        self.update_attribute_without_callbacks(:state, 'completed')
      end
    rescue Exception => e
      if e.message && ( 
                      e.message.starts_with?('This transaction is locked down') ||
                      e.message.starts_with?('This industry type (eCOMMERCE) does not allow a capture greater than the value of the auth') )
        return false # This payment was already captured or the order price changed
      else
        raise
      end
    end

    private
    def record_response(response)
      details = response.doc.to_s if response.respond_to?(:doc)
      details ||= response.to_yaml
      details.gsub!(/AccountNum>\d+<\/AccountNum/, 'AccountNum FILTERED /')
      log_entries.create({:details => details}, :without_protection => true)
    end
  end
end

Spree::Shipment.class_eval do
  attr_accessor :payment_successful

  def shipping_cost
    # shipping cost is for ONLY the first shipment
    order.shipments.shipped.order(:shipped_at).first == self ? order.ship_total : 0
  end

  def price
    # create a dummy order to keep track of the line itmes in the current shipment
    dummy_order = order.dup
    dummy_order.line_items = order.shipped_line_items( self )
    price = dummy_order.line_items.map(&:total).sum
    price -= dummy_order.line_item_discounts
    if (tax_rate = order.tax_rate)
      price += (tax_rate * price).round(2)
    end
    price += shipping_cost
  end

  private
  def after_ship
    update_attribute_without_callbacks :shipped_at, Time.now
    inventory_units.each &:ship!
    self.payment_successful = capture_credit_card_payment_if_needed!
    Spree::OrderMailer.confirm_email(order, false, self).deliver
  end

  def capture_credit_card_payment_if_needed!
    return true unless (payment = order.payments.pending.from_creditcard.first)
    payment.complete_or_partial_capture!( self.price )
  end

end