Mark route as intended for JSON response

[Muffinman]

In terms of validation/exception flow it would be very nice to be able to mark a route as json. Allowing Laravel to know that the intended route was json and should respond accordingly.

My use case:

• We build an API for a user to consume.
• User requests an API endpoint, but does not send valid JSON or Accept: application/json header
• Laravel does not (by default) produce error, it just redirects to homepage with the error bag
• User is confused what they are doing wrong

To fix this, currently the easiest way is to edit app\Exceptions\Handler.php and add some custom route detection to the shouldReturnJson() method. It would be nice if overriding core methods wasn't required, using some route logic.

I've built quite a few APIs with Laravel and I seem to run into this at least once per API.

e.g. Without the Accept header mentioned above, this would just redirect to the Laravel home page.

Route::prefix('api')
    ->group(function() {
        Route::get('/', function() {
            throw ValidationException::withMessages(['error' => 'This is a test']);
        })
    });

If we could add ->json() support, then the default Laravel Exception Handler could check this within shouldReturnJson() and honour it.

Route::prefix('api')
    ->json()
    ->group(function() {
        Route::get('/', function() {
            throw ValidationException::withMessages(['error' => 'This is a test']);
        })
    });