Extract EE-specific lines from issuable finders

app/finders/issues_finder.rb

@@ -128,13 +128,7 @@ class IssuesFinder < IssuableFinder
   end
 
   def by_assignee(items)
-    if assignees.any?
-      assignees.each do |assignee|
-        items = items.assigned_to(assignee)
-      end
-
-      items
-    elsif assignee && assignees.empty?
+    if assignee
       items.assigned_to(assignee)
     elsif no_assignee?
       items.unassigned
@@ -144,17 +138,4 @@ class IssuesFinder < IssuableFinder
       items
     end
   end
-
-  def assignees
-    return @assignees if defined?(@assignees)
-
-    @assignees =
-      if params[:assignee_ids]
-        User.where(id: params[:assignee_ids])
-      elsif params[:assignee_username]
-        User.where(username: params[:assignee_username])
-      else
-        []
-      end
-  end
 end

app/finders/merge_requests_finder.rb

@@ -37,18 +37,6 @@ class MergeRequestsFinder < IssuableFinder
 
   private
 
-  def by_assignee(items)
-    if assignee
-      items = items.where(assignee_id: assignee.id)
-    elsif no_assignee?
-      items = items.where(assignee_id: nil)
-    elsif assignee_id? || assignee_username? # assignee not found
-      items = items.none
-    end
-
-    items
-  end
-
   def source_branch
     @source_branch ||= params[:source_branch].presence
   end

ee/app/finders/ee/issues_finder.rb

@@ -2,6 +2,7 @@ module EE
   module IssuesFinder
     extend ActiveSupport::Concern
     extend ::Gitlab::Utils::Override
+    include ::Gitlab::Utils::StrongMemoize
 
     module ClassMethods
       extend ::Gitlab::Utils::Override
@@ -42,5 +43,30 @@ module EE
     def filter_by_any_weight?
       params[:weight] == ::Issue::WEIGHT_ANY
     end
+
+    override :by_assignee
+    def by_assignee(items)
+      if assignees.any?
+        assignees.each do |assignee|
+          items = items.assigned_to(assignee)
+        end
+
+        return items
+      end
+
+      super
+    end
+
+    def assignees
+      strong_memoize(:assignees) do
+        if params[:assignee_ids]
+          ::User.where(id: params[:assignee_ids])
+        elsif params[:assignee_username]
+          ::User.where(username: params[:assignee_username])
+        else
+          []
+        end
+      end
+    end
   end
 end