Re: Regarding autocalling (was Re: #def woes)

I agree with you on this, but, as you said, it's too big of a change to 
rip it out.

Btw, another way to turn it off, all the time rather than per template, is 
to define a subclass of Cheetah.Template that has a custom set of default 
compiler settings and then use that subclass instead of Cheetah.Template.

On Thu, 21 May 2009, R. Tyler Ballance wrote:

> On Thu, May 21, 2009 at 04:06:16PM -0700, [email protected] wrote:
>>    why do u not like autocalling?
>
> I suppose I should enumerate my objections to the use of autocalling and
> why I harsh on it so much :)
>
> For what autocalling actually does, you can refer to this document:
> 	http://www.cheetahtemplate.org/docs/users_guide_html_multipage/language.namemapper.autocalling.html
>
> My primary issue with autocalling is that I dislike the language being
> "smart", whenever software tries to be "smart" it usually ends up
> screwing things up. What makes programming languages important is that
> they do not only what you tell them, but *only* what you tell them.
>
> Autocalling doesn't quite fit that mold, if you use the NameMapper to
> execute this statement:
>
> 	$foo.bar
>
> Being a Python developer, I would expect this to me an attribute or
> property access of "bar" from the object "foo". With autocalling
> enabled, this isn't quite the case.
>
> Sure $foo.bar can equate to `foo.bar`, but it can also mean `foo['bar']`
> or even `foo.bar()`
>
>
> This can lead to subtle bugs (or lazy developers) if you're not aware
> of this "smartness" on Cheetah's side of the fence. The "workarounds"
> are to do any one of the following:
>
> 	* Compile your templates with --settings="useAutocalling=False"
> 	* Use $getVar('foo.bar', autoCall=False)
> 	* Add `#compiler-settings useAutocalling=False #end
> 	  compiler-settings` to your template
>
> That all said I'm not going to change the behavior because I'm aware of
> how many Cheetah users depend on this functionality.
>
>
> Cheers
>
>>    On Thu, May 21, 2009 at 3:59 PM, R. Tyler Ballance <[email protected]>
>>    wrote:
>>
>>      On Thu, May 21, 2009 at 03:52:08PM -0700, [email protected]
>>      wrote:
>>     >    #def displayfloat($a)
>>     >    $("%.2f"%$a)#slurp
>>     >    #end def
>>     >    #set showfloat = $getVar('displayfloat', autoCall=False)
>>     >
>>     >    ## return a callable value for $name
>>     >    #def callable($name)
>>     >    #return $getVar($name, autoCall=False)
>>     >    #end def
>>     >
>>     >    #set showfloat =$callable('displayfloat')
>>
>>      Dude you're stomping on builtins, you probably shouldn't do that:
>>
>>                    >>> callable
>>                     <built-in function callable>
>>                    >>>
>>
>>      The first example you've got works fine:
>>
>>                    >>> from Cheetah.Template import Template
>>                    >> t = Template('''#def displayfloat(a)
>>                     ... $("%.2f"%$a)#slurp
>>                     ... #end def
>>                     ... #set showfloat = $getVar('displayfloat',
>>      autoCall=False)
>>                     ... $showfloat(3.14)
>>                     ... ''')
>>                    >>> t.respond()
>>                     u'3.14\n'
>>                    >>>
>>
>>      I'm not sure what you're doing, it could be due to overriding the
>>      builtin
>>      callable() function which NameMapper *does* use for lookups (stupid
>>      auto-calling), that's my only guess for why this is failing for you.
>>     >
>>     >    both these options dont work
>>     >        return str(compiled_tmpl)
>>     >      File "/usr/lib/python2.5/site-packages/Cheetah/Template.py", line
>>      997,
>>     >    in __str__
>>     >        return getattr(self, mainMethName)()
>>     >      File "<string>", line 3514, in respond
>>     >    NotFound: cannot find 'showfloat' while searching for 'showfloat'
>>     >
>>     >    On Thu, May 21, 2009 at 2:57 PM, R. Tyler Ballance
>>      <[email protected]>
>>     >    wrote:
>>     >
>>     >      On Thu, May 21, 2009 at 02:55:50PM -0700,
>>      [email protected]
>>     >      wrote:
>>     >     >    #set $faa = self.foo
>>     >     >
>>     >     >    This is cool calling with self. doesnt autocall
>>     >
>>     >      It doesn't call because you're in the right hand operand (where
>>      you need
>>     >      not use Cheetah syntax), and you're not using the '$'. When you
>>      use the
>>     >      $,
>>     >      that invokes the NameMapper which is responsible for autocalling.
>>     >
>>     >      I personally prefer this option to $getVar() which feels
>>      distinctly
>>     >      non-Pythonic ;)
>>     >
>>     >     >    On 5/20/09, Michael Higgins <[email protected]> wrote:
>>     >     >
>>     >     >      On May 20, 2009, at 4:18 PM, R. Tyler Ballance wrote:
>>     >     >
>>     >     >        I /think/ this should work:
>>     >     >               #set $faa = foo
>>     >     >
>>     >     >      I'm not running the latest and greatest, but that doesn't
>>      work
>>     >      for me.
>>     >     >       What *does* work for me is saying
>>     >     >
>>     >     >      #set $faa = self.foo
>>     >     >
>>     >     >      Exploiting self in such an unvarnished way seems like it
>>      might be
>>     >      too
>>     >     >      close to relying on an implementation detail, but maybe
>>      it's
>>     >      okay.  I
>>     >     >      guess Cheetah already has to guarantee not to do
>>      name-mangling or
>>     >     >      something so that Python code can call Cheetah methods
>>     >      properly...
>>     >     >
>>     >     >        Alternatively, you can use:
>>     >     >               #set $faa = $foo
>>     >     >
>>     >     >        If you compile the templates with autocalling disabled
>>     >     >
>>     >     >      Personally, I'm not a huge fan of tweaking the compile
>>      settings a
>>     >      lot
>>     >     >      for different templates.  It's just one more thing that
>>      can
>>     >      mysteriously
>>     >     >      break and take a long time to figure out.
>>     >     >
>>     >     >      To answer mobiledreamer's (later) question about what a
>>      wrapper
>>     >      function
>>     >     >      would look like:
>>     >     >
>>     >     >      ## return a callable value for $name
>>     >     >      #def F($name)
>>     >     >      #return $getVar($name, autoCall=False)
>>     >     >      #end def
>>     >     >
>>     >     >      #set $faa = $F('foo')
>>     >     >
>>     >     >      ... assuming the self trick isn't the preferable style.
>>       (It's
>>     >      certainly
>>     >     >      shorter!)
>>     >     >
>>     >     >      Mike
>>     >     >
>>     >     >    --
>>     >     >    Bidegg worlds best auction site
>>     >     >    http://bidegg.com
>>     >
>>     >      --
>>     >      -R. Tyler Ballance
>>     >      Slide, Inc.
>>     >
>>     >    --
>>     >    Bidegg worlds best auction site
>>     >    http://bidegg.com
>>
>>      --
>>      -R. Tyler Ballance
>>      Slide, Inc.
>>
>>    --
>>    Bidegg worlds best auction site
>>    http://bidegg.com
>
> --
> -R. Tyler Ballance
> Slide, Inc.
>

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