[Python-Dev] proto-pep: plugin proposal (for unittest)

[Michael Foord]

On 30/07/2010 11:09, Tarek Ziadé wrote:
> On Fri, Jul 30, 2010 at 12:55 AM, Michael Foord
> <fuzzyman at voidspace.org.uk>  wrote:
> ...
>    
>> The Plugin Class
>> ================
>>
>> A sometimes-more-convenient way of creating plugins is to subclass the
>> ``unittest2.events.Plugin`` class. By default subclassing ``Plugin`` will
>> auto-instantiate the plugin and store the instance in a list of loaded
>> plugins.
>>
>> Each plugin has a ``register()`` method that auto-hooks up all methods whose
>> names correspond to events. Plugin classes may also provide
>> ``configSection`` and ``commandLineSwitch`` class attributes which
>> simplifies enabling the plugin through the command line and making available
>> a section from the configuration file(s).
>>      
> What about using ABCs here instead ? The big advantage is that you don't force
> people to subclass your Plugin base class,

Is that an advantage? Subclassing Plugin provides functionality rather 
than particularly an interface.

> and you get a registration
> mechanism for free.
>
>    
Actually it looks like it would be *extra* code. (The registration 
mechanism is already "free" to the programmer when they subclass.) I 
will investigate this, but if the only benefit it provides is "you don't 
have to subclass" then I'm not sure there is any point. Note that the 
Plugin class is only "sugar" over hooking up to the events directly 
*anyway*, so there is no *need* to use Plugin to write extensions.

I'm going to read your blog entry on the topic to evaluate it properly 
though:

https://tarekziade.wordpress.com/2009/05/01/basic-plugin-system-using-abcs-and-the-extensions-package/

Michael


> They would be able to explicitly register any class using :
>
>    from unittest2.events import Plugin
>
>    Plugin.register(MySuperPlugin)
>    
>
> Regards
> Tarek
>
>
>    


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

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