Remedy verbose, often unhelpful undefined template variable logging

[Tim Graham]

As ​discussed on django-developers, ticket #18773 added logging of undefined template variables in Django 1.9 [dc5b01ad05e50ccde688c73c2ed3334a956076b0], however, I've seen several reports of users finding this logging more confusing than helpful. For example, ​admin templates log errors about missing is_popup variables which is how the template are designed (is_popup is only in the contexts of pop ups) and the TECHNICAL_404_TEMPLATE (now django/views/templates/technical_404.html) also logs errors (#26886) without any obvious solution about how to prevent that. Also #28516 shows the many warnings logged for an admin changelist page.

[Natalia Bidart]

Ticket #35716 is related, possibly a duplicate.

[Sarah Boyce <42296566+sarahboyce@…>]

In 7894776b:

Refs #28526 -- Provided URLResolver namespace in technical 404 template.

This avoids looking up the nonexistent "name" attribute on URLResolver,
which logs verbosely.

[Mankameshwar Mishra]

Hi, I’d like to work on this ticket if it’s still available. Please let me know if I can take it.

[Tim Graham]

What's your proposal on how to address it?

[Mankameshwar Mishra]

Thanks for the question.

My understanding is that the current logging for undefined template variables can be very verbose and sometimes confusing, especially in cases where missing variables are expected (e.g., optional template context variables).

My proposal is to improve this by making the logging less noisy. For example, we could avoid logging repeated messages for the same undefined variable within a single template render, or adjust the message so it is clearer and more actionable for developers.

I will first investigate where the logging is triggered in the template engine and propose a minimal change that reduces unnecessary verbosity while keeping useful debugging information.

Please let me know if this approach sounds reasonable.

[Tim Graham]

I don't care to engage with contributors using AI.