3 files changed, 17 insertions, 2 deletions
diff --git a/activestorage/lib/active_storage/attached/macros.rb b/activestorage/lib/active_storage/attached/macros.rb
index c51efa9d6b..a87f02efe1 100644
--- a/activestorage/lib/active_storage/attached/macros.rb
+++ b/activestorage/lib/active_storage/attached/macros.rb
@@ -38,7 +38,7 @@ module ActiveStorage
         end
       CODE
 
-      has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record
+      has_one :"#{name}_attachment", -> { where(name: name) }, class_name: "ActiveStorage::Attachment", as: :record, inverse_of: :record, dependent: :delete
       has_one :"#{name}_blob", through: :"#{name}_attachment", class_name: "ActiveStorage::Blob", source: :blob
 
       scope :"with_attached_#{name}", -> { includes("#{name}_attachment": :blob) }
@@ -83,7 +83,7 @@ module ActiveStorage
         end
       CODE
 
-      has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment", inverse_of: :record
+      has_many :"#{name}_attachments", -> { where(name: name) }, as: :record, class_name: "ActiveStorage::Attachment", inverse_of: :record, dependent: :delete_all
       has_many :"#{name}_blobs", through: :"#{name}_attachments", class_name: "ActiveStorage::Blob", source: :blob
 
       scope :"with_attached_#{name}", -> { includes("#{name}_attachments": :blob) }
diff --git a/activestorage/test/models/attachments_test.rb b/activestorage/test/models/attachments_test.rb
index cb52a57b33..a5fcad1bab 100644
--- a/activestorage/test/models/attachments_test.rb
+++ b/activestorage/test/models/attachments_test.rb
@@ -80,6 +80,20 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     end
   end
 
+  test "replace independent attached blob" do
+    @user.cover_photo.attach create_blob(filename: "funky.jpg")
+
+    perform_enqueued_jobs do
+      assert_difference -> { ActiveStorage::Blob.count }, +1 do
+        assert_no_difference -> { ActiveStorage::Attachment.count } do
+          @user.cover_photo.attach create_blob(filename: "town.jpg")
+        end
+      end
+    end
+
+    assert_equal "town.jpg", @user.cover_photo.filename.to_s
+  end
+
   test "attach blob to new record" do
     user = User.new(name: "Jason")
 
diff --git a/activestorage/test/test_helper.rb b/activestorage/test/test_helper.rb
index aaf1d452ea..9b5cd41335 100644
--- a/activestorage/test/test_helper.rb
+++ b/activestorage/test/test_helper.rb
@@ -65,5 +65,6 @@ ActiveRecord::Base.send :include, GlobalID::Identification
 
 class User < ActiveRecord::Base
   has_one_attached :avatar
+  has_one_attached :cover_photo, dependent: false
   has_many_attached :highlights
 end