If you read the documentation for CakePHP on creating PlugIns. It clearly states that the PluginAppModel and PluginAppController base classes extend from the AppModel and AppController classes. Which are implemented in the application using the plugin.
This seems very risky to me.
A plugin doesn’t have control over what callbacks, components, helpers, etc.. that an application may have configured in those base classes.
Is there any problems in having your PluginAppModel/PluginAppController extend just the base classes from the CakePHP lib. Like Model and Controller?
Can someone explain the logic in why a plugin should extend these application specific classes?
Not matter what you do, exclude the App* classes from the inheritage chain or if you include them. There will be always points of possible failure because it is not predictable what people do in these classes.
The less likely scenario is that things break in your plugin if you extend the App* base classes than when you would not extend them.
Auth and Session Component are in the case of a Controller a good reason why you should extend the App* classes. Behaviours in an AppModel another one.
If your plugin depends on a certain – unchanged – state of a property of the Controller or Model class you did something wrong while building that plugin in my opinion. It is better to keep your plugin flexible by providing configuration options or check the states of inherited properties and attached components and behaviours.
If there is really a pitfall in your plugin – I still think it’s done wrong then – you should document it so that it can be integrated properly by people who read the documentation.