Can't save BlobFields when using both django_gcp and django-reverse-admin

Question

I'm trying to use both django-gcp to store large images as BlobFields, and django-reverse-admin so I can edit all of my data inline. My models look like this:

class SceneContent(models.Model):
    site_title = RichCharField(
        max_length=25, verbose_name="Site Title (25 char)", null=True
    )
    site_description = RichTextField(
        max_length=300,
        verbose_name="Site Description (300 char)",
        null=True,
        validators=[MaxLengthValidator(300)],
    )
    site_image = BlobField(
        # blank=True,
        verbose_name="Site Image (3840 x 2160 px)",
        get_destination_path=get_destination_path_image,
        store_key="media",
        null=True,
        validators=[BlobImageExtensionValidator()],
        overwrite_mode="update",
    )

    object_title_1 = RichCharField(
        max_length=25, verbose_name="Object Title 1 (25 char)", null=True
    )
    object_description_1 = RichTextField(
        max_length=300,
        verbose_name="Object Description 1 (300 char)",
        null=True,
    )
    object_image_1 = BlobField(
        # blank=True,
        verbose_name="Object Image 1 (3840 x 2160 px)",
        get_destination_path=get_destination_path_image,
        store_key="media",
        null=True,
        validators=[BlobImageExtensionValidator()],
        overwrite_mode="update",
    )

    object_title_2 = RichCharField(
        max_length=25, verbose_name="Object Title 2 (25 char)", null=True
    )
    object_description_2 = RichTextField(
        max_length=300,
        verbose_name="Object Description 2 (300 char)",
        null=True,
    )
    object_image_2 = BlobField(
        # blank=True,
        verbose_name="Object Image 2 (3840 x 2160 px)",
        get_destination_path=get_destination_path_image,
        store_key="media",
        null=True,
        validators=[BlobImageExtensionValidator()],
        overwrite_mode="update",
    )

    def __str__(self):
        return self.site_title


class Site(models.Model):
    scene_title = RichCharField(
        max_length=12, verbose_name="Title (12 char)", null=True
    )
    pronunciation_guide = RichCharField(
        max_length=25, verbose_name="Site Pronunciation Guide (25 char)", null=True
    )
    scene_subtitle = RichCharField(
        max_length=40, verbose_name="Subtitle (40 char)", null=True
    )
    scene_selection_image = BlobField(
        # blank=True,
        verbose_name="Background Image (1280 x 2160 px)",
        get_destination_path=get_destination_path_image,
        store_key="media",
        null=True,
        validators=[BlobImageExtensionValidator()],
        overwrite_mode="update",
    )
    scene_content = models.OneToOneField(
        SceneContent, on_delete=models.CASCADE, related_name="scene_content", null=True
    )

    def __str__(self):
        return self.scene_title

    class Meta:
        verbose_name = "Site"

And I'm using django-reverse-admin so that when I create a Site in my admin interface, I create my SceneContent inline.

However, when I save the model in my admin interface, I'm getting a MissingBlobError. It appears that when django-gcp goes to copy_blob, the blob is no longer available in its temporary location. My guess is that django-reverse-admin is causing the save order of the OneToOne relationship and parent model to be different than django-gcp is expecting (or the parent models gets saved/validated multiple times), and this is causing the issue.

I've noticed that the parent model (Site) has no issue with saving its BlobField, and I get errors ONLY when saving the BlobField fields in my OneToOne model.

The error is below:

Internal Server Error: /admin/mesoamerica/site/64/change/
Traceback (most recent call last):
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_gcp\storage\operations.py", line 52, in copy_blob
    destination_blob = source_bucket.copy_blob(
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\google\cloud\storage\bucket.py", line 1910, in copy_blob
    copy_result = client._post_resource(
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\google\cloud\storage\client.py", line 627, in _post_resource
    return self._connection.api_request(
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\google\cloud\storage\_http.py", line 72, in api_request
    return call()
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\google\cloud\_http\__init__.py", line 494, in api_request
    raise exceptions.from_http_response(response)
google.api_core.exceptions.NotFound: 404 POST https://storage.googleapis.com/storage/v1/b/my-museum-multimedia/o/_tmp%2Fd1263eb1-0469-4ea4-ace0-272d8ecdefba/copyTo/b/my-museum-multimedia/o/mesoamerica%2Fimages%2FCh1-e8c868fa-f800-47d7-8b67-0e0d0676f2de.png?prettyPrint=false: No such object: 
my-museum-multimedia/_tmp/d1263eb1-0469-4ea4-ace0-272d8ecdefba      

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\core\handlers\exception.py", line 55, in inner
    response = get_response(request)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\core\handlers\base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)   
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\contrib\admin\options.py", line 688, in wrapper
    return self.admin_site.admin_view(view)(*args, **kwargs)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\utils\decorators.py", line 134, in _wrapper_view
    response = view_func(request, *args, **kwargs)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\views\decorators\cache.py", line 62, in _wrapper_view_func
    response = view_func(request, *args, **kwargs)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\contrib\admin\sites.py", line 242, in inner
    return view(request, *args, **kwargs)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_reverse_admin\__init__.py", line 207, in change_view
    return self._changeform_view(request, object_id, form_url, extra_context) 
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_reverse_admin\__init__.py", line 275, in _changeform_view
    self._save_object(request, new_object, form, formsets, add)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_reverse_admin\__init__.py", line 214, in _save_object
    self.save_related(request, form, formsets, change=not add)
  File "D:\Projects\myproject-django-cms\projects\cms\mesoamerica\admin.py", line 56, in save_related
    with transaction.atomic():
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\db\transaction.py", line 307, in __exit__
    connection.set_autocommit(True)
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\db\backends\base\base.py", line 501, in set_autocommit
    self.run_and_clear_commit_hooks()
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django\db\backends\base\base.py", line 779, in run_and_clear_commit_hooks
    func()
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_gcp\storage\fields.py", line 255, in on_commit_valid
    copy_blob(
  File "D:\Projects\myproject-django-cms\projects\cms\env\lib\site-packages\django_gcp\storage\operations.py", line 86, in copy_blob
    raise MissingBlobError(
django_gcp.exceptions.MissingBlobError: Could not complete copy: source blob _tmp/d1263eb1-0469-4ea4-ace0-272d8ecdefba does not exist in bucket my-museum-multimedia

My first thought was to modify the save order; I updated my wsgi.py to include:

def _changeform_view_reverted(self, request, object_id, form_url, extra_context):
    add = object_id is None

    model = self.model
    opts = model._meta

    if add:
        if not self.has_add_permission(request):
            raise PermissionDenied
        obj = None
    else:
        obj = self.get_object(request, unquote(object_id))

        if request.method == "POST":
            if not self.has_change_permission(request, obj):
                raise PermissionDenied
        else:
            if not self.has_view_or_change_permission(request, obj):
                raise PermissionDenied

        if obj is None:
            return self._get_obj_does_not_exist_redirect(request, opts, object_id)

    formsets = []
    model_form = self.get_form(request, obj=obj, change=not add)

    if request.method == "POST":
        form = model_form(request.POST, request.FILES, instance=obj)
        form_validated = form.is_valid()

        if form_validated:
            new_object = self.save_form(request, form, change=not add)
        else:
            new_object = form.instance

        logger.info(
            f"Parent model {new_object} saved or validated. Proceeding to formsets."
        )

        formsets, inline_instances = self._create_formsets(
            request, new_object, change=not add
        )
        formset_inline_tuples = zip(formsets, self.get_inline_instances(request))
        formset_inline_tuples = _remove_blank_reverse_inlines(
            new_object, formset_inline_tuples
        )
        formsets = [t[0] for t in formset_inline_tuples]

        # Step 1: Save the parent model first without inlines
        if form_validated:
            try:
                # Save the parent model first
                self.save_model(request, new_object, form, not add)
                logger.info(f"Parent model {new_object} saved. Saving inlines next.")

                # Step 2: Save normal inlines (non-reverse inlines)
                for formset, inline in formset_inline_tuples:
                    if not isinstance(inline, ReverseInlineModelAdmin):
                        self.save_formset(request, form, formset, change=not add)
                        logger.info(f"Saved normal formset for {inline}.")

                # Step 3: Save reverse inlines with BlobFields after the parent model is saved
                for formset, inline in formset_inline_tuples:
                    if isinstance(inline, ReverseInlineModelAdmin):
                        if formset.is_valid():  # Ensure the formset is valid
                            logger.info(
                                f"Reverse inline formset for {inline.__class__.__name__} is valid."
                            )

                            # Save only the reverse inline forms that have changes
                            for form_instance in formset.forms:
                                if (
                                    form_instance.has_changed()
                                ):  # Check if the form has changes
                                    logger.info(
                                        f"Form {form_instance.__class__.__name__} with instance ID {form_instance.instance.pk if form_instance.instance.pk else 'New'} has changes and will be saved."
                                    )

                                    # Delay saving BlobField to set the relationship first
                                    obj = form_instance.save(
                                        commit=False
                                    )  # Don't save yet

                                    # Set the OneToOneField or ForeignKey relationship on the parent model
                                    setattr(new_object, inline.parent_fk_name, obj)
                                    logger.info(
                                        f"SceneContent relationship set: {inline.parent_fk_name} -> {obj}"
                                    )

                                    # Do not save the object yet to avoid the BlobField being prematurely saved
                                else:
                                    logger.info(
                                        f"Form {form_instance.__class__.__name__} has no changes and will not be saved."
                                    )

                # Step 4: Now save all reverse inline objects (including BlobFields) after the parent model and related objects
                for formset, inline in formset_inline_tuples:
                    if isinstance(inline, ReverseInlineModelAdmin):
                        saved_objects = []  # List to keep track of newly saved objects
                        changed_objects = []  # List to keep track of changed objects
                        deleted_objects = []  # List to keep track of deleted objects
                        forms = [f for f in formset if f.has_changed()]

                        if forms:
                            for form_instance in forms:
                                logger.info(
                                    f"Saving reverse inline object {form_instance.__class__.__name__} (including BlobField)."
                                )
                                # Final save here, including BlobField
                                form_instance.instance.save()

                                if form_instance.instance.pk is None:
                                    saved_objects.append(
                                        form_instance.instance
                                    )  # Track new objects
                                else:
                                    changed_fields = (
                                        form_instance.changed_data
                                    )  # Track changed fields
                                    changed_objects.append(
                                        (form_instance.instance, changed_fields)
                                    )  # Track changed objects and fields

                        # Manually add the saved, changed, and deleted objects to the formset attributes
                        formset.new_objects = saved_objects
                        formset.changed_objects = changed_objects
                        formset.deleted_objects = (
                            deleted_objects  # Add the deleted objects
                        )

                # Re-save the parent object (new_object) to persist the OneToOneField relationship
                new_object.save()

                logger.info(f"All reverse inline objects saved.")

                # Step 5: Log the change and return the appropriate response
                change_message = self.construct_change_message(
                    request, form, formsets, add
                )
                if add:
                    self.log_addition(request, new_object, change_message)
                    return self.response_add(request, new_object)
                else:
                    self.log_change(request, new_object, change_message)
                    return self.response_change(request, new_object)
            except AttemptedOverwriteError:
                form.add_error(
                    None,
                    "A file you uploaded has the same name as an existing file. Please check your filenames and try again.",
                )
                logger.error("Attempted file overwrite error.")
        else:
            logger.error("Form validation failed.")
            form_validated = False
    else:
        # Prepare the dict of initial data from the request.
        initial = dict(request.GET.items())
        for k in initial:
            try:
                f = opts.get_field(k)
            except FieldDoesNotExist:
                continue
            if isinstance(f, models.ManyToManyField):
                initial[k] = initial[k].split(",")
        if add:
            form = model_form(initial=initial)
            prefixes = {}
            for FormSet, inline in self.get_formsets_with_inlines(request):
                prefix = FormSet.get_default_prefix()
                prefixes[prefix] = prefixes.get(prefix, 0) + 1
                if prefixes[prefix] != 1:
                    prefix = "%s-%s" % (prefix, prefixes[prefix])
                formset = FormSet(instance=self.model(), prefix=prefix)
                formsets.append(formset)
        else:
            form = model_form(instance=obj)
            formsets, inline_instances = self._create_formsets(
                request, obj, change=True
            )

    if not add and not self.has_change_permission(request, obj):
        readonly_fields = flatten_fieldsets(self.get_fieldsets(request, obj))
    else:
        readonly_fields = self.get_readonly_fields(request, obj)

    adminForm = helpers.AdminForm(
        form,
        list(self.get_fieldsets(request)),
        self.prepopulated_fields,
        readonly_fields=readonly_fields,
        model_admin=self,
    )
    media = self.media + adminForm.media

    inline_admin_formsets = self.get_inline_formsets(
        request, formsets, self.get_inline_instances(request), obj
    )
    for inline_formset in inline_admin_formsets:
        media = media + inline_formset.media

    context = self.admin_site.each_context(request)
    reverse_admin_context = {
        "title": _(("Change %s", "Add %s")[add]) % force_str(opts.verbose_name),
        "adminform": adminForm,
        "is_popup": False,
        "object_id": object_id,
        "original": obj,
        "media": mark_safe(media),
        "inline_admin_formsets": inline_admin_formsets,
        "errors": helpers.AdminErrorList(form, formsets),
        "app_label": opts.app_label,
    }
    context.update(reverse_admin_context)
    context.update(extra_context or {})
    return self.render_change_form(
        request,
        context,
        form_url=form_url,
        add=add,
        change=not add,
        obj=obj,
    )


ReverseModelAdmin._changeform_view = _changeform_view_reverted

But this didn't resolve the problem - it actually made it so that I'd get MissingBlobErrors when creating the parent model, and then the OneToOne model would save properly.

What else could I try to resolve this issue?