Add final modifier support

[tomzx]

It is clear that having the final keyword applied either to a class in its entirety or on specific methods has an impact on the type of semantic version a change should generate.

I suggest adding the following rules in order to cover this new requirement.

Visibility (public, protected, private) applies to classes/trait methods.

Classes

Classes with final keyword on the class
The case is for a class that already has the final modifier applied to it, but where we're adding/removing methods.

Code	Level	Rule
----	-----	- Added
V017	MINOR	-- Public
V018	PATCH	-- Protected
V030	PATCH	-- Private
----	-----	- Removed
VXXX	MAJOR	-- Public
V022	PATCH	-- Protected
VXXX	PATCH	-- Private

Classes without final keyword on the class but with final keyword on the methods
The case is for a class that does not have the final modifier applied to it and where we're adding/removing methods with the final keyword.

Code	Level	Rule
----	-----	- Added
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	PATCH	-- Private
----	-----	- Removed
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	PATCH	-- Private

Trait

The case is for a trait but where we're adding/removing methods with the final keyword.

Code	Level	Rule
----	-----	- Added
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	MAJOR	-- Private
----	-----	- Removed
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	MAJOR	-- Private

The rule levels are up for discussion.

This creates 14 new rules and use 4 existing rules (not implemented).

Changelog:
2015-02-25: Add separation between final on class and final on methods based on @mikeSimonson feedback.

[mikeSimonson]

Classes with final keyword on the class

Code	Level	Rule	comment
----	-----	- Added
V017	MINOR	-- Public	ok
V018	PATCH	-- Protected	ok
V030	PATCH	-- Private	ok
----	-----	- Removed
VXXX	MAJOR	-- Public	ok
V022	PATCH	-- Protected	ok
VXXX	PATCH	-- Private	ok

Classes without final keyword on the class but with final keyword on the mehods

Code	Level	Rule
----	-----	- Added
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	PATCH	-- Private
----	-----	- Removed
VXXX	MAJOR	-- Public
VXXX	MAJOR	-- Protected
VXXX	PATCH	-- Private

As for the trait

A trait in itself can't be final so the rules makes sense to me.

[mikeSimonson]

http://3v4l.org/OjLfF for the trait behavior

[tomzx]

@mikeSimonson Not sure that demo proves anything. See http://3v4l.org/klGki. Final or not final, it doesn't change a thing.

Final can be applied on trait methods, but not the whole trait itself.

My understanding of trait is basically that you do a copy/paste of what is inside of it and apply it to a class. Final modifier on methods are said to work according to the rfc.

See http://3v4l.org/uhsP9 for an example of a trait being used and its final modifier constraining subclasses from overriding it.

I'm not sure I see why you'd have different levels triggered if the final modifier is applied on a class or a method. To me, having the final keyword on the class means that it is the same as having the final keyword applied to all of the methods. But it appears I am wrong in that regard. Final on class => cannot extend the class, final on methods => cannot override the method in subclasses.

Thus, I do agree there should be a difference between final being on the class or the method. 👍 on the suggested levels.

[mikeSimonson]

Ok, I see what I missed about the the final in the trait, but still it's a bit confusing :-p.

Thanks