Clash: cannot nest twice even when key is Clash class

lib/hashie/clash.rb

@@ -54,7 +54,9 @@ def merge_store(key, *args) #:nodoc:
       case args.length
       when 1
         val = args.first
-        val = self[key].merge(val) if self[key].is_a?(::Hash) && val.is_a?(::Hash)
+        if self[key].is_a?(::Hash) && val.is_a?(::Hash)
+          val = self.class.new(self[key]).merge(val)
+        end
       else
         val = args
       end
@@ -64,22 +66,23 @@ def merge_store(key, *args) #:nodoc:
     end
 
     def method_missing(name, *args) #:nodoc:
-      name = name.to_s
-      if name.match(/!$/) && args.empty?
+      if args.empty? && name.to_s.end_with?('!')
         key = name[0...-1].to_sym
 
-        if self[key].nil?
-          self[key] = Clash.new({}, self)
-        elsif self[key].is_a?(::Hash) && !self[key].is_a?(Clash)
-          self[key] = Clash.new(self[key], self)
+        case self[key]
+        when NilClass
+          self[key] = self.class.new({}, self)
+        when Clash
+          self[key]
+        when Hash
+          self[key] = self.class.new(self[key], self)
         else
           fail ChainError, 'Tried to chain into a non-hash key.'
         end
-
-        self[key]
       elsif args.any?
-        key = name.to_sym
-        merge_store(key, *args)
+        merge_store(name, *args)
+      else
+        super
       end
     end
   end

spec/hashie/clash_spec.rb

@@ -1,8 +1,6 @@
 require 'spec_helper'
 
 describe Hashie::Clash do
-  subject { Hashie::Clash.new }
-
   it 'is able to set an attribute via method_missing' do
     subject.foo('bar')
     expect(subject[:foo]).to eq 'bar'
@@ -45,4 +43,28 @@
     expect(subject[:foo]).to be_nil
     expect(subject[:hello]).to be_nil
   end
+
+  it 'merges multiple bang notation calls' do
+    subject.where!.foo(123)
+    subject.where!.bar(321)
+    expect(subject).to eq(where: { foo: 123, bar: 321 })
+  end
+
+  it 'raises an exception when method is missing' do
+    expect { subject.boo }.to raise_error(NoMethodError)
+  end
+
+  describe 'when inherited' do
+    subject { Class.new(described_class).new }
+
+    it 'bang nodes are instances of a subclass' do
+      subject.where!.foo(123)
+      expect(subject[:where]).to be_instance_of(subject.class)
+    end
+
+    it 'merged nodes are instances of a subclass' do
+      subject.where(abc: 'def').where(hgi: 123)
+      expect(subject[:where]).to be_instance_of(subject.class)
+    end
+  end
 end