Re: Are you using the Unspecified class

On Sat, 27 Jun 2009, R. Tyler Ballance wrote:

> There is a Cheetah internal class called "Unspecified" that I'd like to
> prune from the tree and replace with None, but I'd like to double check
> that you folks aren't using it for anything outside of Cheetah (it seems
> to be a relic in the Cheetah internals that need not exist).

Tyler,
There is a subtle, but important difference between using Unspecified and 
None for the optional args to Template.compile.  'Unspecified' is more 
than just an weird alternate name for None.

Have a look at the valOrDefault func used in Template.compile(). 
If the argument is 'Unspecified' it falls back to the default values 
defined as _CHEETAH_xxx class attributes in the Template class, or 
possibly in a subclass of Template which provides custom defaults (a usage 
pattern I use frequently to avoid repeating stuff throughout my client 
code).  For some arguments/attributes None is a legal value; cacheStore 
and compilerSettings for example.   If you replace Unspecified with 
None, it will become impossible for subclasses to provide their own 
defaults as class attributes as the default compilerSettings=None (etc.) 
in Template.compile() would always trump them.  The same logic applies to 
arguments/attributes that are boolean.

Please leave Unspecified where it is.  It serves a real purpose and 
nothing is gained by removing it.  However, we should probably get rid of 
the redefined Unspecified I just noticed in Tests/SyntaxAndOutput.py.

Cheers,
Tavis


>
>
> Do let me know if you use it
>
> CHeers
>
> -R. Tyler Ballance
> Slide, Inc.
>

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