Rewriting Magento 2 classes vs Plugins
The obvious reason to use a rewrite instead of a plugin is when you need to override a private, protected or final methods.
But also consider the following scenarios.
1st scenario (absolute sort order):
Rewrites can be useful when you need your code to be run before plugins.
I know you can do it by setting the plugin sortOrder, but you cannot be sure your code will always be the first when someone (not you) is going to install 3rd party components.
2nd scenario (exclude code):
If you need to exclude or rewrite just a piece of code in a method, a plugin could be a sub-optimal way.
I know you can use an around plugin and avoid calling the proceed, but this could break other plugins in the stack.
3rd scenario (code style):
You should use rewrites when you need to rewrite a behaviour, plugins should be used to modify the output or run code before/after.
A plugin, should always run the original code to avoid breaking other modules.
My conclusion:
If you can consider a core method as a black box with an input and one output and you are agnostic about its internal mechanisms, then a plugin could be the best option.
If you need to change an internal behavior, a rewrite could be the best option.
Great question, I asked myself the same thing the other day and here's what I came up with:
- First, plugins cannot be used for final methods, final classes and classes created without dependency injection I reckon that's a very specific case but that's one case where you can't use plugins
- Second, you need to keep in mind the definition of a plugin. It is used to work on a method level whereas preferences are used to work on the whole class level. It is not obvious for everyone so it's good to keep that in mind.
- Finally, and I reckon that's the most important, it seems like plugins can only be used to extend the behavior of any public method within a Magento class. Thus it seems like you cannot use plugins with protected/private methods.
Source: Magento U Fundamental Course