[8.x] Fix router for array action within namespaced groups

[imanghafoori1]

While coding in a typical project I found that the router has an inconsistency:

This does not work in web.php since the root namespace of the group gets prepended to the imported controller.

use App\Http\Controllers\TasksController;

Route::middleware(['auth'])->get('{task}/edit', [TasksController::class, 'edit']);

Error: App\Http\Controllers\App\Http\Controllers\TasksController does not exist.

But the original feature does not expect that: #24385

===========

There are 2 solution:

1- if we add a backslash at the start of controller '\'.TasksController:

Route::middleware(['auth'])->get('{task}/edit', ['\\'.TasksController::class, 'edit']);

2- we call the middleware method "After" controller

Route::get('{task}/edit', [TasksController::class, 'edit'])->middleware(['auth']);

• I added a test to demonstrate the bug, without the change it does not pass.
• To be fully backward-compatible it only adds backslash if it is not already included.

[GrahamCampbell]

I think this is a major breaking change? Stops people from using namespaces?

[GrahamCampbell]

That said, I agree the namespacing feature maybe isn't so useful anymore if people are mostly using class notation now, so we maybe could consider making your proposed behaviour the default in Laravel 9, and possibly going further and removing namespacing stuff.

[imanghafoori1]

I remember, the possibilty of referencing methods in routes was added in 5.6 in the PR #24385
And I always used it like this:
Route::get(...) -> middleware(... ) ;

The unexpected thing happed when I only turned the method calls around:
Route::middleware(...) ->get(...) ;

The second way requires '\'. but not the first way.
And that is because the the get method called behind the scenes is different when you do the it the second way.

[imanghafoori1]

@GrahamCampbell
I changed the implementation so that it only adds the backslash only it is not at the beginning to be fully backward compatible.
and I also added a test to simulate user code for both cases:

Route::middleware('auth')->get('{task}/edit', ['\\'.TasksController::class, 'edit']);
Route::middleware('auth')->get('{task}/edit', [     TasksController::class, 'edit']);

I think with the route cache the production performance will be the same.

[taylorotwell]

I'm confused. Of course it doesn't work. You said your RouteServiceProvider defines a namespace? So, it will be prepended. This is exactly how Laravel 7.x worked.

[taylorotwell]

No plans to change this behavior.