Make sure Relation responds to dynamic finder methods

activerecord/lib/active_record/relation.rb

@@ -143,7 +143,15 @@ module ActiveRecord
     end
 
     def respond_to?(method)
-      @relation.respond_to?(method) || Array.method_defined?(method) || super
+      return true if @relation.respond_to?(method) || Array.method_defined?(method)
+
+      if match = DynamicFinderMatch.match(method)
+        return true if @klass.send(:all_attributes_exists?, match.attribute_names)
+      elsif match = DynamicScopeMatch.match(method)
+        return true if @klass.send(:all_attributes_exists?, match.attribute_names)
+      else
+        super
+      end
     end
 
     def to_a

activerecord/test/cases/relations_test.rb

@@ -142,7 +142,15 @@ class RelationTest < ActiveRecord::TestCase
     relation = Topic.scoped
 
     ["map", "uniq", "sort", "insert", "delete", "update"].each do |method|
-      assert relation.respond_to?(method), "Topic.all should respond to #{method.inspect}"
+      assert relation.respond_to?(method), "Topic.scoped should respond to #{method.inspect}"
+    end
+  end
+
+  def test_respond_to_dynamic_finders
+    relation = Topic.scoped
+
+    ["find_by_title", "find_by_title_and_author_name", "find_or_create_by_title", "find_or_initialize_by_title_and_author_name"].each do |method|
+      assert relation.respond_to?(method), "Topic.scoped should respond to #{method.inspect}"
     end
   end