[Zope-CMF] Re: [dev] some questions regarding Exceptions

[Tres Seaver]

On Tue, 2003-09-16 at 06:59, Yuppie wrote:
> Hi!
> 
> 
> Seb Bacon wrote:
> > Yuppie wrote:
> >> Something like this?
> >>
> >>   class CMFError(StandardError):
> >>     ...
> >>   class MembershipError(CMFError):
> >>     ...
> >>   class MetadataError(CMFError):
> >>     ...
> >>   ...
> > 
> > 
> > Definitely.  I can imagine it might be worth discussing the exception 
> > hierarchy a bit.
> 
> After rereading the python docs, I think the root exception has to be
> 
>    class CMFError(Exception):
> 
> Thats the easy part.
> 
> 
> For the hierarchy I see two possible approaches:
> 
> a) by type (CMFValueError, CMFUnauthorizedError, ...)
> 
> b) by module/context (MembershipError, MetadataError, ...)
> 
> We also could combine these two:
> 
>    class MembershipValueError(ValueError, CMFError):
>    class MembershipUnauthorizedError(Unauthorized, CMFError):
>    class MetadataValueError(ValueError, CMFError):
>    class MetadataUnauthorizedError(Unauthorized, CMFError):
>    ...
> 
> 
> I attached the result of grepping CMF 1.4. Currently both approaches 
> exist. The combined solution would provide the best backwards 
> compatibility, but I'm afraid that's overkill.
> 
> I'd prefer approach b).

-1.  The existing exception types have well-understood semantics;  the
new "module-centric" ones would not.  In particular, third-party code
which currently does::

   except ValueErrror, err:

must continue to work, which implies one of:

  - status quo ante

  - approach a)

  - approach "c)" ;)

Tres.
-- 
===============================================================
Tres Seaver                                tseaver at zope.com
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