lib/attr/gather/aggregators/deep_merge.rb in attr-gather-1.4.0 vs lib/attr/gather/aggregators/deep_merge.rb in attr-gather-1.5.1

@@ -11,15 +11,22 @@
       class DeepMerge < Base
         # Initialize a new DeepMerge aggregator
         #
         # @param reverse [Boolean] deep merge results in reverse order
         # @param merge_input [Boolean] merge the result with the initial input
+        # @param array_strategy [Symbol] strategy for handling arrays, one of (:concat, :overwrite)
         #
         # @api private
-        def initialize(reverse: false, merge_input: true, **)
+        def initialize(reverse: false, merge_input: true, array_strategy: :concat, **)
+          unless ARRAY_STRATEGY.include?(array_strategy)
+            raise ArgumentError, 'array_strategy must be one of: :concat, :overwrite'
+          end
+
           @reverse = reverse
           @merge_input = merge_input
+          @array_strategy = array_strategy
+
           super
         end
 
         def call(input, execution_results)
           execution_results = execution_results.reverse_each if reverse?
@@ -29,21 +36,40 @@
           end
         end
 
         private
 
-        def reverse?
-          @reverse
-        end
+        ARRAY_STRATEGY = %i[concat overwrite].freeze
 
+        private_constant :ARRAY_STRATEGY
+
         def deep_merge(hash, other)
-          Hash[hash].merge(other) do |_, orig, new|
+          hash.to_h.merge(other) do |_, orig, new|
             if orig.respond_to?(:to_hash) && new.respond_to?(:to_hash)
-              deep_merge(Hash[orig], Hash[new])
+              deep_merge(orig.to_h, new.to_h)
+            elsif concattable?(orig, new)
+              orig + new
             else
               new
             end
           end
+        end
+
+        def concattable?(orig, new)
+          return false unless @array_strategy == :concat
+
+          concattable_class?(orig) && concattable_class?(new)
+        end
+
+        def concattable_class?(obj)
+          return true if obj.is_a?(Array)
+          return true if obj.is_a?(Set)
+
+          false
+        end
+
+        def reverse?
+          @reverse
         end
       end
     end
   end
 end