Restore previous behavior of clearing attachments via attribute assig…

…nment

Fixes #2654, Refs. #2613

lib/carrierwave/mount.rb

@@ -174,12 +174,8 @@ def write_#{column}_identifier
           return if frozen?
           mounter = _mounter(:#{column})
 
-          if mounter.remove?
-            mounter.clear!
-            write_uploader(mounter.serialization_column, nil)
-          elsif mounter.identifiers.first
-            write_uploader(mounter.serialization_column, mounter.identifiers.first)
-          end
+          mounter.clear! if mounter.remove?
+          write_uploader(mounter.serialization_column, mounter.identifiers.first)
         end
 
         def #{column}_identifier
@@ -353,12 +349,8 @@ def write_#{column}_identifier
           return if frozen?
           mounter = _mounter(:#{column})
 
-          if mounter.remove?
-            mounter.clear!
-            write_uploader(mounter.serialization_column, nil)
-          elsif mounter.identifiers.any?
-            write_uploader(mounter.serialization_column, mounter.identifiers)
-          end
+          mounter.clear! if mounter.remove?
+          write_uploader(mounter.serialization_column, mounter.identifiers.presence)
         end
 
         def #{column}_identifiers

lib/carrierwave/orm/activerecord.rb

@@ -91,6 +91,11 @@ def remove_#{column}=(value)
           result
         end
 
+        def write_#{column}_identifier
+          return unless has_attribute?(_mounter(:#{column}).serialization_column)
+          super
+        end
+
         # Reset cached mounter on record reload
         def reload(*)
           @_mounters = nil

spec/orm/activerecord_spec.rb

@@ -681,6 +681,21 @@ def filename
       end
 
     end
+
+    describe 'calling #update! on the instance' do
+      before do
+        @event.image = stub_file('test.jpeg')
+        @event.save!
+        @event.reload
+      end
+
+      it "allows clearing the stored image" do
+        @event.update!(image: nil)
+        expect(@event.image.file).to be_nil
+        expect(File.exist?(public_path('uploads/test.jpeg'))).to be_falsy
+        expect(@event[:image]).to be_nil
+      end
+    end
   end
 
   describe '#mount_uploader with mount_on' do
@@ -1509,6 +1524,21 @@ def filename
       end
 
     end
+
+    describe 'calling #update! on the instance' do
+      before do
+        @event.images = [stub_file('test.jpeg')]
+        @event.save!
+        @event.reload
+      end
+
+      it "allows clearing the stored images" do
+        @event.update!(images: [])
+        expect(@event.images).to be_empty
+        expect(File.exist?(public_path('uploads/test.jpeg'))).to be_falsy
+        expect(@event[:images]).to be nil
+      end
+    end
   end
 
   describe '#mount_uploaders with mount_on' do