Deprecation for TemplateResponse and SimpleTemplateResponse accepting django.template.Template is broken

[David Reitter]

When TemplateResponse or SimpleTemplateResponse are called, a TypeError is thrown.

This is because their __init__() creates a BackendTemplate` giving only one argument to the constructor.

The resulting error is obviously confusing and obfuscates the warning.

The attached patch addresses the issue, although I am unsure whether one should assume, by default, that a DjangoTemplate was given.

[Tim Graham]

Can you provide code to reproduce the issue? I'm not entirely clear on it based on the description. Is the issue relevant on master or only in 1.9 that has the deprecation path? If only 1.9, the problem may not be severe enough to warrant being patched there.

I edited the description to change BaseTemplateResponse to SimpleTemplateResponse since there's no class in Django with the former name. Please edit again if it should be something else.

[David Reitter]

Yes, that change of yours is correct (my mistake).

The code that caused it is really quite simple. It just makes a TemplateResponse based on Template without the engine. This came up because I transitioned a Django 1.5 project to 1.9.

The code that produces the exception seems to be meant to handle outdated code like this.

from django.template import Template
from django.template.response import TemplateResponse

def results(request):
       content = "…"
       t = Template(content)
       return TemplateResponse(request, t)

[Tim Graham]

Oh, I had trouble understanding your patch and the problem. The issue is that the backwards compatibility shim crashes. If you are able to add tests for the patch and send a pull request, that would be great.

from django.template import Template
from django.template.response import TemplateResponse
from django.http import HttpRequest

request = HttpRequest()
content = "…"
t = Template(content)
response = TemplateResponse(request, t)
...
  File "/home/tim/code/django/django/template/response.py", line 28, in __init__
    template = BackendTemplate(template)
TypeError: __init__() missing 1 required positional argument: 'backend'

[David Reitter]

Sorry, I looked into writing a test and pretty much got stuck with what seemed to be the test scripts running the system install of Django rather than the code in the checkout.
I won’t have the time to submit more than the patch I submitted, due to various professional obligations. Apologies.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 3fedfc45:

[1.9.x] Fixed #26253 -- Fixed crashing deprecation shims in SimpleTemplateResponse.

Thanks David Reitter for the report and initial patch.

[Tim Graham <timograham@…>]

In 061a7ff3:

[1.8.x] Refs #26253 -- Added tests for deprecation shims in SimpleTemplateResponse.

Backport of 3fedfc452fa94f8a6c9a64289d00202313ceb564 from stable/1.9.x

[Tim Graham <timograham@…>]

In c6ab81db:

[1.9.x] Refs #26253 -- Amended release note as this issue doesn't affect 1.8.

[Tim Graham <timograham@…>]

In 33a4040d:

Refs #26253 -- Forwardported release note.