Jacob Kaplan-Moss wrote:
> On Sat, May 17, 2008 at 11:30 PM, James Bennett <[EMAIL PROTECTED]> wrote:
>> The impression I get is that a lot of people rely on silent *variable*
>> failure, but very few rely on silent *tag* failure. In fact, most
>> real-world custom template tags I've seen are wired up to raise errors
>> quite loudly, and the few times I've tried to write tags which fail
>> silently it's been a laborious process that results in much more
>> brittle code.
>
> Well said. I can't see making ``{{ foo.bar.baz }}`` fail loudly --
> it's just too big a change. It especially sucks when ``foo`` or
> ``bar`` is a dynamically-constructed dictionary with variable keys.
Yes, probably too big a change to make ``{{ foo.bar.baz }}`` fail loudly
at this point (even though there are things like the default filter and
the firstof tag that could facilitate such a change).
I would, however, be in favor for making the exception-catching a bit
smarter here so that we don't suppress exceptions raised by a called
method. For example, I'm ok with:
{{ foo.calculate_number }}
failing silently if no calculate_number attribute/method exists for foo,
but if calculate_number is a method and happens to raise an exception
when called, I want that to bubble up and fail loudly. Otherwise,
hunting down the error becomes more of a chore. Besides, the motivation
behind the silent behavior seems to be more for missing attributes.
> I think taking a close look at built-in *tags*, though, is a good idea
> -- in general, tags should fail loudly. There are exceptions, of
> course; ``{% if dict.somekey %}`` is a common idiom which translates
> to something like ``if dict.has_key('somekey') and dict.somekey`` --
> this is good.
I also agree that, in many instances, tags should fail loudly, and that
these types of failures need to be looked at on a tag by tag basis. The
question then becomes, do we want to always raise these exceptions or do
we want to only raise them if settings.TEMPLATE_DEBUG is True?
Gary
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