I used to do that too (string_if_invalid that raises an exception). What
was nice about this, is you could explicitly wrap the variable in an if tag
to silence the error if you were ok with it. (I'm not sure if this behavior
is still true.)
{% if var_that_sometimes_exists %}{{ var_that_sometimes_exists }}{% endif %}
On Thu, Aug 24, 2017 at 11:59 AM, Sjoerd Job Postmus <sjoerd...@sjec.nl>
wrote:
> As an anecdotal data-point: at the company I'm working at, we are running
> Django with a custom object as "string_if_invalid" that raises an exception
> on string-interpolation. This way missing template variables *do* get
> converted to an exception. I myself am very happy with this solution, as it
> forces us to make sure templates and views match up correctliy. The essence
> is that it's better to get an exception, than incorrect output (Yes, you
> should test beforehand, but sometimes there's a combinatorial explosion
> that makes that hard).
>
>
> On Thursday, August 24, 2017 at 5:21:38 PM UTC+2, Tim Graham wrote:
>>
>> We received a report that shows the large number of undefined variable
>> warnings when rendering an admin changelist page [0].
>>
>> I'm still not sure what the solution should be, but I created #28526 [1]
>> to track this problem: finding a remedy to the problem of verbose, often
>> unhelpful logging of undefined variables.
>>
>> I don't think "the end goal of errors raising when using undefined
>> variables" is feasible. My sense is that relying on the behavior of
>> undefined variables is too entrenched in the Django template language to
>> change it at this point. (If someone wanted to try to fix all the warnings
>> in the admin templates, that might provide a useful data point). See the
>> "Template handling of undefined variables" thread [2] for a longer
>> discussion.
>>
>> [0] https://code.djangoproject.com/ticket/28516
>> [1] https://code.djangoproject.com/ticket/28526
>> [2] https://groups.google.com/d/topic/django-developers/LT5ESP0w
>> 0gQ/discussion
>>
>> On Tuesday, June 20, 2017 at 4:12:52 AM UTC-4, Anthony King wrote:
>>>
>>> -1 for removing logs. Like Vlastimil, it's helped me spot a couple of
>>> stray bugs.
>>>
>>> What I'd actually like to see is this becoming stricter, with the end
>>> goal of errors raising when using undefined variables.
>>>
>>> For the verbosity, perhaps there's a middle ground? only log once per
>>> variable access per template context, and provide a formatter that will
>>> clean up the output?
>>>
>>> I believe in debug mode, you have access to line numbers and character
>>> positions, so the final output could look something like this:
>>>
>>> ``
>>> some_app/home.html:32:24: Undefined variable: *missing_variable*
>>> ``
>>>
>>> I'm unsure how much effort this would take, but it would definitely make
>>> the logging a lot more user + developer friendly.
>>>
>>> On 20 June 2017 at 08:48, Vlastimil Zíma <vlas...@ziima.cz> wrote:
>>>
>>>> -1 to the removal. I was annoyed by the logging at first, but then I
>>>> started to clean individual logs. Half way through, I found several usages
>>>> of long removed variables, one unused template (as a side effect) and I
>>>> updated several views to always provide defined context variables.
>>>>
>>>> All in all, I consider the warnings very useful for a cleaning, though
>>>> I wouldn't be against an option to silence them. Which can already by
>>>> accomplished by LOGGING, can't it?
>>>>
>>>> Vlastik
>>>>
>>>> Dne neděle 26. března 2017 11:14:23 UTC+2 Melvyn Sopacua napsal(a):
>>>>>
>>>>> On Thursday 16 March 2017 12:03:07 Tim Graham wrote:
>>>>>
>>>>> > Ticket #18773 [0] added logging of undefined template variables in
>>>>>
>>>>> > Django 1.9 [1], however, I've seen several reports of users finding
>>>>>
>>>>> > this logging more confusing than helpful.
>>>>>
>>>>>
>>>>>
>>>>> With channels hitting 2.0 and the already large stack of moving parts
>>>>> surrounding Django you need some basic system administration skills and
>>>>> programming experience to work with the system. And there are quite a few
>>>>> examples to link to from the user's list that deal with those moving parts
>>>>> rather then Django itself. It is not an application that you
>>>>> download, install and run.
>>>>>
>>>>>
>>>>>
>>>>> An introduction "What you need to know before starting Django" would
>>>>> help a lot in this respect and explaining the noisiness of some logging
>>>>> belongs in there.
>>>>>
>>>>>
>>>>>
>>>>> Because it *is* useful if you defined that variable to True in your
>>>>> settings, and it's working in all projects but this one. It could be
>>>>> there's an extra piece of context middleware that uses the same name and
>>>>> deletes the variable from the context. It could be there's a Mixin missing
>>>>> in the view hierarchy. Or a typo you don't notice anymore after plowing
>>>>> through 20+ included template bits.
>>>>>
>>>>>
>>>>>
>>>>> Noisy logging is exactly what you want when debugging. It should log
>>>>> things that may be working as designed, especially things that are
>>>>> ambiguous (like undefined and false).
>>>>>
>>>>>
>>>>>
>>>>> Another thing is that logging is the ugly duckling of Django. It's not
>>>>> mentioned much if at all in the tutorial. It is not mentioned at all in
>>>>> "How to write reusable apps" and it shows in the eco system. It's like
>>>>> finding a diamond when an app actually has logging implemented.
>>>>>
>>>>>
>>>>>
>>>>> But it also means that novice users touching the LOGGING configuration
>>>>> are exceptions and I don't think Django should cater to the exceptions.
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> Melvyn Sopacua
>>>>>
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