Merge pull request rails#42224 from abhaynikam/41862-active-storage-has-many-attached-with-nested-attributes

Fixes ActiveStorage#has_many_attached re-creating destroyed attachment

Author: eileencodes

activestorage/lib/active_storage/attached/changes/create_many.rb

@@ -7,6 +7,7 @@ class Attached::Changes::CreateMany #:nodoc:
     def initialize(name, record, attachables)
       @name, @record, @attachables = name, record, Array(attachables)
       blobs.each(&:identify_without_saving)
+      attachments
     end
 
     def attachments
@@ -35,13 +36,16 @@ def build_subchange_from(attachable)
         ActiveStorage::Attached::Changes::CreateOneOfMany.new(name, record, attachable)
       end
 
-
       def assign_associated_attachments
-        record.public_send("#{name}_attachments=", attachments)
+        record.public_send("#{name}_attachments=", persisted_or_new_attachments)
       end
 
       def reset_associated_blobs
         record.public_send("#{name}_blobs").reset
       end
+
+      def persisted_or_new_attachments
+        attachments.select { |attachment| attachment.persisted? || attachment.new_record? }
+      end
   end
 end

activestorage/test/models/attached/many_test.rb

@@ -648,6 +648,24 @@ def highlights
     assert_match(/Cannot find variant :unknown for User#highlights_with_variants/, error.message)
   end
 
+  test "successfully attaches new blobs and destroys attachments marked for destruction via nested attributes" do
+    append_on_assign do
+      town_blob = create_blob(filename: "town.jpg")
+      @user.highlights.attach(town_blob)
+      @user.reload
+
+      racecar_blob = fixture_file_upload("racecar.jpg")
+      @user.update(
+        highlights: [racecar_blob],
+        highlights_attachments_attributes: [{ id: town_blob.id, _destroy: true }]
+      )
+
+      assert @user.reload.highlights.attached?
+      assert_equal 1, @user.highlights.count
+      assert_equal "racecar.jpg", @user.highlights.blobs.first.filename.to_s
+    end
+  end
+
   private
     def append_on_assign
       ActiveStorage.replace_on_assign_to_many, previous = false, ActiveStorage.replace_on_assign_to_many

activestorage/test/test_helper.rb

@@ -128,6 +128,8 @@ class User < ActiveRecord::Base
   has_many_attached :highlights_with_variants do |attachable|
     attachable.variant :thumb, resize: "100x100"
   end
+
+  accepts_nested_attributes_for :highlights_attachments, allow_destroy: true
 end
 
 class Group < ActiveRecord::Base