Update validations

app/controllers/concerns/checkout_callbacks.rb

@@ -28,6 +28,7 @@ module CheckoutCallbacks
   def load_order
     @order = current_order
     @order.manual_shipping_selection = true
+    @order.checkout_processing = true
 
     redirect_to(main_app.shop_path) && return if redirect_to_shop?
     redirect_to_cart_path && return unless valid_order_line_items?

app/models/spree/order.rb

@@ -24,6 +24,9 @@ module Spree
       go_to_state :complete
     end
 
+    attr_accessor :use_billing
+    attr_accessor :checkout_processing
+
     token_resource
 
     belongs_to :user, class_name: Spree.user_class.to_s
@@ -79,8 +82,6 @@ module Spree
     before_validation :associate_customer, unless: :customer_id?
     before_validation :ensure_customer, unless: :customer_is_valid?
 
-    attr_accessor :use_billing
-
     before_create :link_by_email
     after_create :create_tax_charge!
 
@@ -137,6 +138,13 @@ module Spree
     scope :by_state, lambda { |state| where(state: state) }
     scope :not_state, lambda { |state| where.not(state: state) }
 
+    def initialize(*_args)
+      @checkout_processing = nil
+      @manual_shipping_selection = nil
+
+      super
+    end
+
     # For compatiblity with Calculator::PriceSack
     def amount
       line_items.inject(0.0) { |sum, li| sum + li.amount }
@@ -625,7 +633,7 @@ module Spree
 
     # Determine if email is required (we don't want validation errors before we hit the checkout)
     def require_email
-      return true unless new_record? || (state == 'cart')
+      return true unless (new_record? || cart?) && !checkout_processing
     end
 
     def ensure_line_items_present

app/models/spree/order/checkout.rb

@@ -75,7 +75,6 @@ module Spree
 
               before_transition to: :delivery, do: :create_proposed_shipments
               before_transition to: :delivery, do: :ensure_available_shipping_rates
-              before_transition to: :payment, do: :validate_shipping_method!
               before_transition to: :payment, do: :create_tax_charge!
               before_transition to: :confirmation, do: :validate_payment_method!
 
@@ -140,16 +139,8 @@ module Spree
 
           private
 
-          def validate_shipping_method!
-            return unless Flipper.enabled?(:split_checkout)
-            return if shipping_method.present?
-
-            errors.add :shipping_method, I18n.t('split_checkout.errors.select_a_shipping_method')
-            throw :halt
-          end
-
           def validate_payment_method!
-            return unless Flipper.enabled?(:split_checkout)
+            return unless checkout_processing
             return if payments.any?
 
             errors.add :payment_method, I18n.t('split_checkout.errors.select_a_payment_method')