Plugins: SpyderPluginWidget - __init__() vs register_plugin()

[anatoly techtonik]

What is the purpose of register_plugin() if Spyder plugins need to include __init__() function anyway for calling parent constructors? I can't see any significant differences in what should and should not be done in either of these obligatory plugin functions.

[anatoly techtonik]

I can understand the case when plugin doesn't inherit from SpyderPluginWidget, but merely implements its interface, but it still will be a class and class constructor is called anyway.

[Pierre Raybaut]

There are a couple of reasons why I wrote the 'register_plugin' in Spyder's plugins interface:

  * the 'register_plugin' method is doing more than a constructor should do: it registers the plugin to Spyder's main window (connecting signals, ...) -- I tend to avoid constructor methods that do everything: it's less readable

  * separating this method from the constructor also has the advantage of making it easier to change the code structure in the future

  * there is another reason/motivation for this, but I can't remember it -- my guess is that was at some point essential to create this method but the situation changed and now it's not as needed as it was (except for the reasons above)

[anatoly techtonik]

Following this philosophy, how about removing `parent` parameter to plugin constructor and pass it to register_plugin() instead? In this case plugin constructor will just provide a placeholder for storing reference to parent Spyder window, which is passed to register_plugin() that does all other complicated logic like calling SpyderPluginMixin.initilialize_plugin() etc.

The benefit of that:

 - discourage users from doing too much stuff in __init__() (obviously they can't do much without a reference to Spyder's main window)

 - add ability to control if plugin failed to register by checking return code of register_plugin() function