Implement ruby 2.6 hash merging.

As of ruby 2.6, Hash#merge and Hash#merge! allow for multiple hashes
to be passed to the method, and will merge each one in the order that
they were passed.

2 files changed, 41 insertions, 5 deletions

diff --git a/lib/hashie/mash.rb b/lib/hashie/mash.rb
index bac93a4..888b4f6 100644
--- a/lib/hashie/mash.rb
+++ b/lib/hashie/mash.rb
@@ -251,11 +251,39 @@ module Hashie
     def deep_merge(other_hash, &blk)
       dup.deep_update(other_hash, &blk)
     end
-    alias merge deep_merge
 
     # Recursively merges this mash with the passed
     # in hash, merging each hash in the hierarchy.
     def deep_update(other_hash, &blk)
+      _deep_update(other_hash, &blk)
+      self
+    end
+
+    with_minimum_ruby('2.6.0') do
+      # Performs a deep_update on a duplicate of the
+      # current mash.
+      def deep_merge(*other_hashes, &blk)
+        dup.deep_update(*other_hashes, &blk)
+      end
+
+      # Recursively merges this mash with the passed
+      # in hash, merging each hash in the hierarchy.
+      def deep_update(*other_hashes, &blk)
+        other_hashes.each do |other_hash|
+          _deep_update(other_hash, &blk)
+        end
+        self
+      end
+    end
+
+    # Alias these lexically so they get the correctly defined
+    # #deep_merge and #deep_update based on ruby version.
+    alias merge deep_merge
+    alias deep_merge! deep_update
+    alias update deep_update
+    alias merge! update
+
+    def _deep_update(other_hash, &blk)
       other_hash.each_pair do |k, v|
         key = convert_key(k)
         if v.is_a?(::Hash) && key?(key) && regular_reader(key).is_a?(Mash)
@@ -266,11 +294,8 @@ module Hashie
           custom_writer(key, value, false)
         end
       end
-      self
     end
-    alias deep_merge! deep_update
-    alias update deep_update
-    alias merge! update
+    private :_deep_update
 
     # Assigns a value to a key
     def assign_property(name, value)
diff --git a/spec/hashie/mash_spec.rb b/spec/hashie/mash_spec.rb
index 837a7f1..e2a178c 100644
--- a/spec/hashie/mash_spec.rb
+++ b/spec/hashie/mash_spec.rb
@@ -1046,4 +1046,15 @@ describe Hashie::Mash do
       end
     end
   end
+
+  with_minimum_ruby('2.6.0') do
+    context 'ruby 2.6 merging' do
+      subject(:mash) { Hashie::Mash.new(model: 'Honda') }
+      it 'merges multiple hashes and mashes passeed to #merge' do
+        first_hash = { model: 'Ford' }
+        second_hash = { model: 'DeLorean' }
+        expect(mash.merge(first_hash, second_hash)).to eq('model' => 'DeLorean')
+      end
+    end
+  end
 end