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.
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.
A final note: if you want loud variable failures, it's a pretty
trivial task to write a template tag that echoes a variable or raises
an exception; you could then use ``{% require foo.bar.baz %}`` instead
of ``{{ foo.bar.baz }}``. I'll leave the actual implementation up to
the intrepid reader; it's just a few lines of code.
Jacob
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