[Python-Dev] PEP 376 proposed changes for basic plugins support

[Michael Foord]

On 02/08/2010 19:45, Holger Krekel wrote:
> On Mon, Aug 2, 2010 at 8:12 PM, Michael Foord<fuzzyman at voidspace.org.uk>  wrote:
>    
>> On 02/08/2010 19:05, Holger Krekel wrote:
>>      
>>> On Mon, Aug 2, 2010 at 6:57 PM, Ian Bicking<ianb at colorstudy.com>    wrote:
>>>
>>>        
>>>> Just to add a general opinion in here:
>>>>
>>>> Having worked with Setuptools' entry points, and a little with some Zope
>>>> pluginish systems (Products.*, which I don't think anyone liked much, and
>>>> some ways ZCML is used is pluginish), I'm not very excited about these.
>>>>   The
>>>> plugin system that causes the least confusion and yet seems to accomplish
>>>> everything it needs is just listing objects in configuration -- nothing
>>>> gets
>>>> activated implicitly with installation, and names are Python
>>>> package/object
>>>> names without indirection.
>>>>
>>>>          
>>> This makes it a two-step process to use a plugin: install it and then
>>> configure it correctly to have it used.
>>>
>>> I'd much prefer a one-step process and rather provide a way to not-use
>>> a plugin even if installed.  The difference is e.g. with py.test that i
>>> can
>>> point users to e.g.
>>>
>>>    pip install pytest-figleaf
>>>    py.test --figleaf
>>>
>>>        
>> How do you achieve this currently?
>>      
> it uses setuptools entrypoints, so with a setup.py param like
>    

Right. I can't use that for unittest. With the new proposal we *could* 
automatically use all available plugins, but I think I prefer to only 
have plugins active that the user has chosen.

Michael

>      entry_points = {'pytest11': ['pytest_figleaf = pytest_figleaf'],},
>
> py.test's pluginmanager.py does:
>
>          for ep in pkg_resources.iter_entry_points('pytest11'):
>              # ... ep.name == "pytest_figleaf"<- left side of above "*=*"
>              plugin = ep.load() #<- right side of above "*=*"
>              # ...
>
> best,
> holger
>
>
>    
>> Michael
>>
>>      
>>> instead of also having to explain a configuration file, its location
>>> and exact content or some magic attribute variables on some
>>> classes.
>>>
>>> TBH, i'd like to have pip handle plugins, based on metadata
>>> (especially some data signaling something is a plugin of otherthing).
>>> This way i only once have to teach about "pip" and people leverage
>>>   their knowledge for installing/managing plugins.
>>>
>>> best,
>>> holger
>>>
>>>
>>>        
>>>> The only thing I'd want to add is the ability to
>>>> also point to files, as a common use for plugins is adding ad hoc
>>>> functionality to an application, and the overhead of package creation
>>>> isn't
>>>> always called for.  hg for example seems both simple and general enough,
>>>> and
>>>> it doesn't use anything fancy.
>>>>
>>>> Purely for the purpose of discovery and documentation it might be helpful
>>>> to
>>>> have APIs, then some tool could show available plugins (especially if
>>>> PyPI
>>>> had a query interface for this), or at least installed plugins, with the
>>>> necessary code to invoke them.
>>>>
>>>> *Maybe* it would make sense to generalize the discovery of plugin types,
>>>> so
>>>> that you can simply refer to an object and the application can determine
>>>> what kind of plugin it is.  But having described this, it actually
>>>> doesn't
>>>> seem like a useful thing to generalize.
>>>>
>>>> --
>>>> Ian Bicking  |  http://blog.ianbicking.org
>>>>
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>>>>
>>>>
>>>>          
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>>>        
>>
>> --
>> http://www.ironpythoninaction.com/
>> http://www.voidspace.org.uk/blog
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>>      


-- 
http://www.ironpythoninaction.com/
http://www.voidspace.org.uk/blog

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