Added block to deep merge extension

CHANGELOG.md

@@ -6,6 +6,7 @@
 * [#252](https://github.com/intridia/hashie/pull/252): Add support for conditionally required Hashie::Dash attributes - [@ccashwell](https://github.com/ccashwell).
 * [#256](https://github.com/intridia/hashie/pull/256): Inherit key coercions - [@Erol](https://github.com/Erol).
 * [#259](https://github.com/intridia/hashie/pull/259): Fix handling of default proc values in Mash - [@Erol](https://github.com/Erol).
+* [#260](https://github.com/intridia/hashie/pull/260): Add block to deep merge extension - [@galathius](https://github.com/galathius).
 * Your contribution here.
 
 ## 3.3.2 (11/26/2014)

lib/hashie/extensions/deep_merge.rb

@@ -2,28 +2,32 @@ module Hashie
   module Extensions
     module DeepMerge
       # Returns a new hash with +self+ and +other_hash+ merged recursively.
-      def deep_merge(other_hash)
-        dup.deep_merge!(other_hash)
+      def deep_merge(other_hash, &block)
+        dup.deep_merge!(other_hash, &block)
       end
 
       # Returns a new hash with +self+ and +other_hash+ merged recursively.
       # Modifies the receiver in place.
-      def deep_merge!(other_hash)
-        _recursive_merge(self, other_hash)
+      def deep_merge!(other_hash, &block)
+        _recursive_merge(self, other_hash, &block)
         self
       end
 
       private
 
-      def _recursive_merge(hash, other_hash)
-        if other_hash.is_a?(::Hash) && hash.is_a?(::Hash)
-          other_hash.each do |k, v|
-            hash[k] = hash.key?(k) ? _recursive_merge(hash[k], v) : v
-          end
-          hash
-        else
-          other_hash
+      def _recursive_merge(hash, other_hash, &block)
+        other_hash.each do |k, v|
+          hash[k] = if hash[k].is_a?(::Hash) && v.is_a?(::Hash)
+                      _recursive_merge(hash[k], v, &block)
+                    else
+                      if block_given? && hash.key?(k)
+                        block.call(k, hash[k], v)
+                      else
+                        v
+                      end
+                    end
         end
+        hash
       end
     end
   end

spec/hashie/extensions/deep_merge_spec.rb

@@ -7,16 +7,35 @@ class DeepMergeHash < Hash
 
   subject { DeepMergeHash }
 
-  let(:h1) { subject.new.merge(a: 'a', a1: 42, b: 'b', c: { c1: 'c1', c2: { a: 'b' }, c3: { d1: 'd1' } }) }
-  let(:h2) { { a: 1, a1: 1, c: { c1: 2, c2: 'c2', c3: { d2: 'd2' } } } }
-  let(:expected_hash) { { a: 1, a1: 1, b: 'b', c: { c1: 2, c2: 'c2', c3: { d1: 'd1', d2: 'd2' } } } }
 
-  it 'deep merges two hashes' do
-    expect(h1.deep_merge(h2)).to eq expected_hash
+  context 'without &block' do
+    let(:h1) { subject.new.merge(a: 'a', a1: 42, b: 'b', c: { c1: 'c1', c2: { a: 'b' }, c3: { d1: 'd1' } }) }
+    let(:h2) { { a: 1, a1: 1, c: { c1: 2, c2: 'c2', c3: { d2: 'd2' } } } }
+    let(:expected_hash) { { a: 1, a1: 1, b: 'b', c: { c1: 2, c2: 'c2', c3: { d1: 'd1', d2: 'd2' } } } }
+
+    it 'deep merges two hashes' do
+      expect(h1.deep_merge(h2)).to eq expected_hash
+    end
+
+    it 'deep merges another hash in place via bang method' do
+      h1.deep_merge!(h2)
+      expect(h1).to eq expected_hash
+    end
   end
 
-  it 'deep merges another hash in place via bang method' do
-    h1.deep_merge!(h2)
-    expect(h1).to eq expected_hash
+  context 'with &block' do
+    let(:h1) { subject.new.merge(a: 100, b: 200, c: { c1: 100 }) }
+    let(:h2) { { b: 250, c: { c1: 200 } } }
+    let(:expected_hash) { { a: 100, b: 450, c: { c1: 300 } } }
+    let(:block) { Proc.new { |_, this_val, other_val| this_val + other_val } }
+
+    it 'deep merges two hashes' do
+      expect(h1.deep_merge(h2, &block)).to eq expected_hash
+    end
+
+    it 'deep merges another hash in place via bang method' do
+      h1.deep_merge!(h2, &block)
+      expect(h1).to eq expected_hash
+    end
   end
 end