Allow user to be guest when using the @can directive

[yaquawa]

PR Type

refactor + behavior change

Changes

currently, if we use the @can directive, the current user must be authenticated.

while Laravel itself allow the $user to be either a guest or an authenticated user by specifying the first argument ($user) as a nullable argument or an argument with the default value with null in the policy class's methods. This PR make it aligned to the Laravel's can method.

The authentication check logic should be separate from this directive, for example the @middleware is the best place to do that.

Additionally, I found use the keyword ability is more understandable in most of cases(aligned to Laravel's naming convention) than using if, so I added an option to allow user to use ability instead of if.

Last thing that might worth to mention is that I separated the validation logic into the validate method to get more extensibility. I found validation logic can varies quite differently in some cases. Making the validation logic stay in a method so one can make a new directive by extending the CanDirective class and change it's behavior very easily.

[spawnia]

Can you please add comprehensive tests for the behaviour you added? Not merging this as is.

[yaquawa]

Hi @spawnia 😄
I added some tests, but I don't know if this is good enough for you😅

plus the test will fail if the version of Laravel is less than 5.7, because this is the new behavior as of ver 5.7.

https://github.com/laravel/framework/blob/5.7/src/Illuminate/Auth/Access/Gate.php#L365-L407

[spawnia]

This is looking pretty good, can you add a few lines to the master docs on how to use this?

Possibly with a hint that guest user functionality requires Laravel 5.7.

[yaquawa]

@spawnia Done!

[spawnia]

Thanks @yaquawa

[chrissm79]

Excellent work @yaquawa, thank you!