Re: [Rest2web-develop] None and Defaults

[Michael F. <mi...@pc...>]

Nicola Larosa wrote:
>>I have a question about your changes to validate regarding None :
>>
>>Specifically this code :
>>        if missing:
>>            try:
>>                value = fun_kwargs['default']
>>            except KeyError:
>>                raise ValidateMissingValue
>>        # None is an admissible value for all types
>>        if isinstance(value, StringTypes) and (value.lower() == 'none'):
>>            return None
>>
>>This means that the string 'none' in a value will *always* be converted
>>to ``None``. I think this should only happen if 'none' is the default
>>value and the value itself is missing.
> 
> 
> Maybe somebody would like to explicitly put a None value in the config
> value, instead of just omitting it and having to say "default = None" in
> the configspec. Maybe the default is something else, and there's a need to
> unset a value in the config.
> 
> I'm cool with the "None" string, by itself, always meaning the None value,
> like True or False, but not restricted to one check type. Maybe we should
> take out that "lower" method, though.
> 

I'm not - ConfigObj shouldn't change the type without the programmer
specifying it.

Don't forget the value is set by the *user* - not the programmer.
ConfigObj should only convert type if the programmer says. None
shouldn't be an acceptable value for every check - maybe it *isn't* an
acceptable value (what if the programmer really does want an integer
there - he expects validate to tell him).

> 
> 
>>Also - in case validate is called later ``None`` ought to always go
>>through (e.g. to verify user changes to the config file made via a GUI).
> 
> 
> That's right, I didn't think about that, good catch.
> 
> 
> 
>>These two changes make the code (I think) :
>>
>>        if missing:
>>            try:
>>                value = fun_kwargs['default']
>>            except KeyError:
>>                raise ValidateMissingValue
>>            # None is an admissible value for all types
>>            if isinstance(value, StringTypes) and (value.lower() == 'none'):
>>                value = None
>>        if value is None:
>>            return None
> 
> 
> Then it would become something like:
> 
>          if missing:
>              try:
>                  value = fun_kwargs['default']
>              except KeyError:
>                  raise ValidateMissingValue
>          # None is an admissible value for all types
>          if (value is None) or (value == 'None'):
>              return None
> 

This means that someone's program will break because a user enters
'None' as a string value. It ought to be possible to have 'None' as a
string value in a config file without our program converting it to
another type.

I thought the point was to catch defaults ?

My proposed (and currently committed) solution allows the programmer to
specify that None is ok (by using default='None'), which makes the value
explicitly (user sets value as 'None') and implicitly (user omits value
altogether) optional. I'm fine with removing the 'lower'.

All the best,

Fuzzy