Fix ActiveStorage has_one_attached when blob or record are not persisted

- Purging a not persisted blob no longer raise a `FrozenError`.
- Purging a not persisted record no longer raise an `ActiveRecord::ActiveRecordError`.

Fixes #37069

activestorage/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Allow to purge an attachment when record is not persisted for `has_one_attached`
+
+    *Jacopo Beschi*
+
 *   Add a load hook called `active_storage_variant_record` (providing `ActiveStorage::VariantRecord`)
     to allow for overriding aspects of the `ActiveStorage::VariantRecord` class. This makes
     `ActiveStorage::VariantRecord` consistent with `ActiveStorage::Blob` and `ActiveStorage::Attachment`

activestorage/app/models/active_storage/attachment.rb

@@ -23,7 +23,7 @@ class ActiveStorage::Attachment < ActiveStorage::Record
   def purge
     transaction do
       delete
-      record&.touch
+      record.touch if record&.persisted?
     end
     blob&.purge
   end
@@ -32,7 +32,7 @@ def purge
   def purge_later
     transaction do
       delete
-      record&.touch
+      record.touch if record&.persisted?
     end
     blob&.purge_later
   end

activestorage/app/models/active_storage/blob.rb

@@ -293,8 +293,9 @@ def delete
   # blobs. Note, though, that deleting the file off the service will initiate an HTTP connection to the service, which may
   # be slow or prevented, so you should not use this method inside a transaction or in callbacks. Use #purge_later instead.
   def purge
+    previously_persisted = persisted?
     destroy
-    delete
+    delete if previously_persisted
   rescue ActiveRecord::InvalidForeignKey
   end
 

activestorage/lib/active_storage/attached.rb

@@ -16,6 +16,10 @@ def initialize(name, record)
       def change
         record.attachment_changes[name]
       end
+
+      def reset_changes
+        record.attachment_changes.delete(name)
+      end
   end
 end
 

activestorage/lib/active_storage/attached/one.rb

@@ -61,6 +61,7 @@ def purge
       if attached?
         attachment.purge
         write_attachment nil
+        reset_changes
       end
     end
 
@@ -69,6 +70,7 @@ def purge_later
       if attached?
         attachment.purge_later
         write_attachment nil
+        reset_changes
       end
     end
 

activestorage/test/models/attached/one_test.rb

@@ -481,6 +481,22 @@ def upload.open
     end
   end
 
+  test "purging when record is not persisted" do
+    create_blob(filename: "funky.jpg").tap do |blob|
+      user = User.new
+      user.avatar.attach blob
+      assert user.avatar.attached?
+
+      attachment = user.avatar.attachment
+      user.avatar.purge
+
+      assert_not user.avatar.attached?
+      assert attachment.destroyed?
+      assert_not ActiveStorage::Blob.exists?(blob.id)
+      assert_not ActiveStorage::Blob.service.exist?(blob.key)
+    end
+  end
+
   test "purging later" do
     create_blob(filename: "funky.jpg").tap do |blob|
       @user.avatar.attach blob
@@ -517,6 +533,24 @@ def upload.open
     end
   end
 
+  test "purging an attachment later when record is not persisted" do
+    create_blob(filename: "funky.jpg").tap do |blob|
+      user = User.new
+      user.avatar.attach blob
+      assert user.avatar.attached?
+
+      attachment = user.avatar.attachment
+      perform_enqueued_jobs do
+        user.avatar.purge_later
+      end
+
+      assert_not user.avatar.attached?
+      assert attachment.destroyed?
+      assert_not ActiveStorage::Blob.exists?(blob.id)
+      assert_not ActiveStorage::Blob.service.exist?(blob.key)
+    end
+  end
+
   test "purging dependent attachment later on destroy" do
     create_blob(filename: "funky.jpg").tap do |blob|
       @user.avatar.attach blob

activestorage/test/models/blob_test.rb

@@ -245,6 +245,13 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     end
   end
 
+  test "purge doesn't raise when blob is not persisted" do
+    build_blob_after_unfurling.tap do |blob|
+      assert_nothing_raised { blob.purge }
+      assert blob.destroyed?
+    end
+  end
+
   test "uses service from blob when provided" do
     with_service("mirror") do
       blob = create_blob(filename: "funky.jpg", service_name: :local)