Allow closures when calling throw_if

[chrispage1]

This enhancement allows defining the exception provided to the throw_if helper as a Closure.

The closure should return either the exception to be thrown or the class type of the exception represented as a string.

This is a quality of life improvement. Take the following:

// a success will return true while a failure will return an instance of CustomResponse
$apiResponse = app()->call(MakeApiCall::class);

// the below will result in an error because the exception creation logic is always run
throw_if($apiResponse instanceof CustomResponse, new \Exception($apiResponse->message));

// by wrapping it in a closure, it'll only be evaluated when our if is truthy
throw_if($apiResponse instanceof CustomResponse, fn() => new \Exception($apiResponse->message));

I have added this functionality with testing and the ability to preserve existing functionality, such as passing parameters through to the closure. It also gets evaluated first so that the response can then be further processed, e.g. you could return an exception class type from the closure.

Thanks!

[taylorotwell]

Should the docblock of throw_unless be updated? Anywhere else?

[chrispage1]

Should the docblock of throw_unless be updated? Anywhere else?

Good point - I have updated throw_unless - I can't see any other implementations that require additional documentation other than that. Thanks Taylor.