[6.x] Fix RouteUrlGenerator accepting empty string for required paramenter

[MrCrayon]

#30659 fixed RouteUrlGenerator not failing when a required parameter is not passed but it's still not failing if a required parameter is passed empty.

Route::get('/foo/{required}/test/{optional?}')->name('test-route');

route('test-route', ['required' => null, 'optional' => null]);
// UrlGenerationException

route('test-route', ['required' => '', 'optional' => null]);
// /foo//test

I don't think this could be considered an expected behaviour since normally required means set and not empty.

My PR checks if the required parameter is set and it's not an empty string, if this check fails it will look for default Parameter and as last step checks if parameter was optional.

[driesvints]

@MrCrayon tests are failing and you probably want to add a test specifically for this scenario.

[MrCrayon]

@driesvints yes, it's quite strange that route failing on tests it's ok on my end.

Route::get('foo/bar/{baz}')->name('foobar');

route('foobar', ['baz' => 'Taylor']);
// /foo/bar/Taylor

I'll add some tests and try to understand what's happening.

[MrCrayon]

Test failing was the one with optional parameter passed without key:

Route::get('foo/bar/{baz?}')->name('foobar');

route('foobar', 'taylor');
// or
route('foobar', ['taylor']);

What I needed to do is removing empty parameter from $parameters and let the other methods take care of the rest.

[driesvints]

@MrCrayon this broke a scenario where 0 is used as a route parameter: #30760

[Vercoutere]

Just wanted to add that this was a breaking change for us too, not because we were using 0 as a parameter, but because we were actually relying on an empty string passing through the system.

It allowed to use an optional subdomain with the following pattern:

Route::pattern('subdomain', '(^[a-z0-9\-]+\.)*');

Kind of bummed this doesn't work anymore as I don't see another straight forward way for us to implement the same behaviour.

[MrCrayon]

@Vercoutere check is intended for required parameters but you should still be able to use an optional parameter
https://laravel.com/docs/6.x/routing#parameters-optional-parameters

[Vercoutere]

@MrCrayon that's right, but unfortunately optional parameters only seem to work when they are the last parameter in a given route. Using an optional parameter for a subdomain, followed by a domain parameter, followed by a URI with other parameters doesn't work.