[Zope3-dev] RFC: Use ConfigParser for High-Level Configuration

[Dieter Maurer]

Jim Fulton wrote at 2006-3-12 15:54 -0500:
>Dieter Maurer wrote:
>> Jim Fulton wrote at 2006-3-11 18:03 -0500:
>> 
>>>...
>>>Where is this documented?
>> 
>> 
>> I do not know. I saw a feature description in the mailing list.
>> Fred and Tres (the authors) should be able to tell you whether
>> there is a formal documentation and where you can find it.
>> 
>> 
>>>Let's pursue this a bit.
>>>
>>>Would it be possible to write a configuration file that loaded
>>>it's own schemas?
>> 
>> 
>> Yes -- with some restrictions: as I described in my previous mail.
>> 
>>   The feature essentially works as follows:
>> 
>>      You have an abstract section type in your primary
>>      schema, usually usable in a multisection.
>> 
>>        Examples: ZServer server, ZODB storage, the general extension
>>        abstract section type
>> 
>>      In your module/package, you define your own section type
>>      implementing the abstract section type in its "component.xml".
>>      You are completely free in its keys and subsections.
>> 
>>      In the configuration file, you import your module/package (which
>>      makes available the definitions in its "component.xml") and
>>      instantiate one or more of the section types defined there.
>> 
>>      Your application/module looks for the sections of "its" type
>>      and uses them.
>> 
>>   The restriction: you cannot have new keys on the top level -- all
>>   must be nested in a section type defined by your "component.xml".
>>   But, this, I consider an advantage (ZConfig here behave similar
>>   to a "ConfigParser" approach).
>
>So the example I gave won't work.  In a schema, I have to have an
>abstract type for each thing I might want to add.  But I don't know what
>I want to add.  This doesn't sound very extensible.

You can have a *SINGLE* abstract type -- fixed for any extensions
you may imagine and use this as the hook in your "component.xml".

Such a single abstract type was added to the Zope schema to
make almost arbitrary extensions possible.

>I can't fathom the ZConfig documentation so I don't really know what
>an abstract type is.

It is essentially a name, which can be used at various places
in your schema and implemented at other places in different ways.

> I don't know how restrictive it has to be.
>Can I define an abstract type that matched anything?

Yes. I even think you currently cannot impose restrictions on
the sectiontypes claiming to implement the abstract type.

>Can I define a schema that just defines an abstract type that
>matches anything?

I think you must also use the abstract type in a section/multisection
definition. But that would be all.



-- 
Dieter