Byron,
I agree, for certain type of applications Velocity should be set to
follow strict rules(mainly to throw exceptions as soon as possible
instead logging).
I know Nathan changed some parts to follow a strict mode and some
sections throws exceptions now instead of logging the failure(actually
both), but I think your idea with a more restrictive context could fill
up some needs, at least I would like to have something like that. If the
template access something that doesn't exists I would like to fail(fast).
Byron Foster wrote:
On Sep 29, 2008, at 4:34 , [EMAIL PROTECTED] wrote:
Hi,
Thanks for your thoughts (and possible contributions). Here some
further ideas.
In the past the Velocity design avoided by all means to become Perl
like.
I can appreciate that :)
Since there is a simpler workaround, I believe a "~=" operator can be
avoided (in Perl it would mean to be a pattern matcher).
I've got a patch I will post next for review/feedback which uses the
following
syntax: #set($!foo = "bar"). The bang was pretty easy to implement
with the current code (No parse alterations), and I think the syntax
works.
So please use:
#if($foo == $null)#set($foo = "bar")#end
This works fine now, but I'm making a setting that will throw an
exception for variables and method that are not defined. In this
context the if statement would not work because $foo would not be
defined yet, causing an exception to be thrown.
or (using a context tool in the context):
#if(!$context.isKey($foo))#set($foo = "bar")#end
or wrap the above in a macro and use it:
#optionalDefault($foo "bar")
Fair enough, even though I might think it's a little obscure.
On the null reference issue, I proposed in an early Velocity to allow
a silent assign notation, in the line of:
#set($!foo = null)
to allow foo=null and to not log anything. This approach would allow
the designer to specify where he expects nulls to go through.
Unhappily it overlapped with another patch and did not make it into
the core.
Ahh, well I used the same syntax in the coming patch, but for a
different purpose.
To my knowledge since velocity 1.6 (1.5?) a null value can be
assigned to a context key, when enabled by a property.
Not really, currently it is implement such that if a variable is
assigned null, then the variable is deleted from the context. While
currently this distinction is of little consequence, if variables must
be strictly defined then it is important that #set($foo = $null) is
still considered a set variable, and carried in the context.
Currently the notation
#set($foo = $!bar.baz)
should not log if baz is undefined. You should also consider this
silent notation operator in your object check.
But my intent is for this NOT to be silent if baz is undefined, but
rather immediately throw an exception! and to take this one step
further, throw an exception if even $bar is not defined.
Combining this with my proposed syntax:
#set($!foo = $!bar.baz)
means to not complain that baz is null and silently assign it to the
$foo in the context.
I believe there is a group of us Velocity users which would like to
see references handled more strictly. I realize this is a preference,
so I had intended, of course, to create an option to turn such
behavior on using 'runtime.references.strict'. In my personal
experience, whenever a property is undefined, or a variable, it is
always because of a typo, or because code has been re-factored and a
property doesn't exist anymore. In my usage the current behavior
makes finding these problems difficult, especially when such
referenced are buried several macro levels deep. It also makes unit
testing trickier, for me at least :)
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