Cannot import csrf_input_lazy from partially initialized module.

[thommy]

Hi,

most of the time a TemplateView using Jinja2 is working fine, but sometimes I get the following exception. I wasn't able to figure out why it happens:

ImportError: cannot import name 'csrf_input_lazy' from partially initialized module 'django.template.backends.utils' (most likely due to a circular import) (/srv/pydl/env/lib/python3.9/site-packages/django/template/backends/utils.py)
  File "django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
  File "django/core/handlers/base.py", line 220, in _get_response
    response = response.render()
  File "django/template/response.py", line 114, in render
    self.content = self.rendered_content
  File "django/template/response.py", line 92, in rendered_content
    return template.render(context, self._request)
  File "django/template/backends/jinja2.py", line 65, in render
    from .utils import csrf_input_lazy, csrf_token_lazy

The view looks like this:

class ScriptView(TemplateView):
    """View for Tcl scripts"""

    template_engine = "jinja2"
    content_type = "text/x-tcl"

    extra_context = {"fqdn": settings.FQDN}

And it is used like the following:

    path(
        "script.tcl",
        views.ScriptView.as_view(template_name="script.tcl.j2"),
        name="script",
    ),

Is it a race condition in conjunction with the Jinja2 template backend or is TemplateView not supposed to be used like this?

Is it possible to force pre-loading the required modules?

Best regards
Thommy

[Mariusz Felisiak]

Tentatively accepted (similar to the #33420). Can you confirm that the following patch works for you:

django/template/backends/jinja2.py

@@ -8 +8 @@
 from django.utils.module_loading import import_string
 
 from .base import BaseEngine
+from .utils import csrf_input_lazy, csrf_token_lazy
 
 
 class Jinja2(BaseEngine):
@@ -62 +63 @@
         )
 
     def render(self, context=None, request=None):
-        from .utils import csrf_input_lazy, csrf_token_lazy
-
         if context is None:
             context = {}
         if request is not None:

[thommy]

Hi Mariusz,

thanks for the quick response. I'll give it a try.

However it might take a couple of days to be sure because the problem happens so rarely.

Best regards
Thommy

[thommy]

Hi Mariusz,

happy new year!

So far the exception hasn't occured again.

It would be great to see this patch in one of the next bugfix releases :-)

Best regards
Thommy

[Mariusz Felisiak]

Replying to thommy:

Hi Mariusz,

happy new year!

The same to you!

So far the exception hasn't occured again.

That's great! Would you like to prepare PR?

It would be great to see this patch in one of the next bugfix releases :-)

Per our backporting policy it doesn't qualify for a backport, so it can be fixed in Django 4.2, see ​Django’s release process for more details.

[rajdesai24]

hey Mariusz would love to draft a PR

[Mariusz Felisiak]

Replying to rajdesai24:

hey Mariusz would love to draft a PR

Thanks, please prepare PR, see my comment. There is nothing more to do, IMO.

[rajdesai24]

Please find the ​PR

[thommy]

Thank you :-)

[GitHub <noreply@…>]

In d5f892d8:

Fixed #34220 -- Moved csrf_input_lazy, csrf_token_lazy imports to the toplevel.

This prevents random errors with partially initialized modules.