[Validator] Only validate newly submitted attachables

lib/active_storage_validations/shared/asv_attachable.rb

@@ -29,9 +29,13 @@ def attachables_from_changes(record, attribute)
       changes = record.attachment_changes[attribute.to_s]
       return [] if changes.blank?
 
-      Array.wrap(
-        changes.is_a?(ActiveStorage::Attached::Changes::CreateMany) ? changes.attachables : changes.attachable
-      ).uniq
+      newly_submitted_attachables = if changes.is_a?(ActiveStorage::Attached::Changes::CreateMany)
+        (changes.attachables - record.public_send("#{attribute}_blobs"))
+      else
+        changes.attachable
+      end
+
+      Array.wrap(newly_submitted_attachables).uniq
     end
 
     # Retrieve the full declared content_type from attachable.

test/validators/shared_examples/works_fine_with_attachables.rb

@@ -255,6 +255,36 @@ def fixture_file_upload(filename, mime_type = nil, binary = false)
         end
       end
 
+      describe "when attaching new files to a has_many relationship that already has files" do
+        let(:attachable_1) do
+          {
+            io: File.open(png_image),
+            filename: 'image_150x150.png',
+            content_type: 'image/png'
+          }
+        end
+
+        let(:attachable_2) do
+          {
+            io: File.open(png_image),
+            filename: 'image_150x150_28ko.png',
+            content_type: 'image/png'
+          }
+        end
+
+        before do
+          subject.using_attachables.attach([attachable_1])
+          subject.save!
+        end
+
+        it "only perform the validation on the new files" do
+          assert_called_on_instance_of(validator_class, :is_valid?, times: 1) do
+            subject.using_attachables.attach([attachable_2])
+            subject.valid?
+          end
+        end
+      end
+
       describe "when doing an update" do
         before do
           subject.using_attachables.attach([attachable_1])