Fix deep_merge function, added custom implementation for pure Ruby

lib/valvat/configuration.rb

@@ -71,7 +71,7 @@ def dig(*keys)
     end
 
     def configure(options)
-      @data = @data.deep_merge(Utils.deep_symbolize_keys(options))
+      @data = Utils.deep_merge(@data, Utils.deep_symbolize_keys(options))
     end
 
     def initialize

lib/valvat/utils.rb

@@ -45,5 +45,10 @@ def self.deep_symbolize_keys(value)
         val.is_a?(Hash) ? deep_symbolize_keys(val) : val
       end
     end
+
+    def self.deep_merge(original_hash, hash_to_merge)
+      merger = proc { |_key, v1, v2| v1.is_a?(Hash) && v2.is_a?(Hash) ? v1.merge(v2, &merger) : v2 }
+      original_hash.merge(hash_to_merge, &merger)
+    end
   end
 end

spec/valvat/utils_spec.rb

@@ -122,4 +122,25 @@
       expect(described_class.deep_symbolize_keys({ 'a' => 1, :b => { 'c' => 3 } })).to eql({ a: 1, b: { c: 3 } })
     end
   end
+
+  describe '#deep_merge' do
+    let(:original_hash) { { a: 1, b: { c: 3 }, e: { w: 9 } } }
+    let(:hash_to_merge) { { b: { d: 4 }, e: { w: 10 }, y: 11 } }
+
+    it 'deep merge the nested hashes' do
+      expect(described_class.deep_merge(original_hash, hash_to_merge)).to eql(
+        {
+          a: 1,
+          b: {
+            c: 3,
+            d: 4
+          },
+          e: {
+            w: 10
+          },
+          y: 11
+        }
+      )
+    end
+  end
 end