From 98dbc146f9c01fc7811cc863b7219a83ee257bdb Mon Sep 17 00:00:00 2001
From: dtaniwaki <daisuketaniwaki@gmail.com>
Date: Wed, 11 Mar 2015 12:22:01 -0700
Subject: [PATCH 1/2] Skip merging if the destination is nil

---
 lib/deep_merge/core.rb | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/deep_merge/core.rb b/lib/deep_merge/core.rb
index 374ae77..a6cba26 100644
--- a/lib/deep_merge/core.rb
+++ b/lib/deep_merge/core.rb
@@ -92,9 +92,13 @@ def self.deep_merge!(source, dest, options = {})
       source.each do |src_key, src_value|
         if dest.kind_of?(Hash)
           puts "#{di} looping: #{src_key.inspect} => #{src_value.inspect} :: #{dest.inspect}" if merge_debug
-          if dest[src_key]
-            puts "#{di} ==>merging: #{src_key.inspect} => #{src_value.inspect} :: #{dest[src_key].inspect}" if merge_debug
-            dest[src_key] = deep_merge!(src_value, dest[src_key], options.merge(:debug_indent => di + '  '))
+          if dest.has_key?(src_key)
+            if dest[src_key].nil?
+              puts "#{di} ==>skipping: #{src_key.inspect} => #{src_value.inspect} :: #{dest[src_key].inspect}" if merge_debug
+            else
+              puts "#{di} ==>merging: #{src_key.inspect} => #{src_value.inspect} :: #{dest[src_key].inspect}" if merge_debug
+              dest[src_key] = deep_merge!(src_value, dest[src_key], options.merge(:debug_indent => di + '  '))
+            end
           else # dest[src_key] doesn't exist so we want to create and overwrite it (but we do this via deep_merge!)
             puts "#{di} ==>merging over: #{src_key.inspect} => #{src_value.inspect}" if merge_debug
             # note: we rescue here b/c some classes respond to "dup" but don't implement it (Numeric, TrueClass, FalseClass, NilClass among maybe others)

From d28c22ef9cf1afc203b527f0297430d3817322d4 Mon Sep 17 00:00:00 2001
From: dtaniwaki <daisuketaniwaki@gmail.com>
Date: Wed, 11 Mar 2015 12:29:45 -0700
Subject: [PATCH 2/2] Add tests for skip merge on nil destination

---
 test/test_deep_merge.rb | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/test/test_deep_merge.rb b/test/test_deep_merge.rb
index 836c8af..fa03c9b 100644
--- a/test/test_deep_merge.rb
+++ b/test/test_deep_merge.rb
@@ -604,5 +604,20 @@ def test_deep_merge
     hash_src = {"item" => s2 }
     DeepMerge::deep_merge!(hash_src, hash_dst)
     assert_equal({"item" => ""}, hash_dst)
+
+    ################################
+    # Test ignoring nil destination
+
+    # if the destination is nil, skip merging it
+    hash_src = {"foo" => {"bar" => 1} }
+    hash_dst = {"foo" => {"bar" => nil} }
+    DeepMerge::deep_merge!(hash_src, hash_dst)
+    assert_equal({"foo" => {"bar" => nil}}, hash_dst)
+
+    # if the destination does not exists, merge it
+    hash_src = {"foo" => {"bar" => 1} }
+    hash_dst = {"foo" => {} }
+    DeepMerge::deep_merge!(hash_src, hash_dst)
+    assert_equal({"foo" => {"bar" => 1}}, hash_dst)
   end # test_deep_merge
 end