[9.x] Add Eloquent mode to prevent silently discarding fills for attributes not in $fillable

[ralphjsmit]

One very irritating thing for me is to forget adding a new property to the $fillable array (because it's not my default way of working) and later discover that fills have been silently discarded, thus causing bugs.

Personally I always unguard my models using $guarded = [], because I know from myself that I never do anything like $model->update($request->all()). However, sometimes you join a new project where it's the convention to always use the $fillable array.

Currently Eloquent only throws an exception when the model is "totally guarded". This PR adds a method that is similar to the Model::preventLazyLoading() to also throw exceptions when a model change was discarded:

Model::preventDiscardingGuardedAttributeFills();

It also works with a boolean:

Model::preventDiscardingGuardedAttributeFills(! app()->isProduction());

Naming ideas are appreciated. I tried to come up with a shorter name, but I couldn't yet think of a name that could convey the behaviour in a better and shorter way.

People can also add a callback to handle the exception. The callback receives the model, the key and the value of the attribute:

Model::handleMassAssignmentViolationUsing(function(Model $model, string $key, mixed $value) {
    //
});

I think this would be very useful to prevent bugs on local environments when the developer forgets to add an attribute to $fillable. Thanks!

[foremtehan]

add tests to your codes, thank you.

[ralphjsmit]

add tests to your codes, thank you.

I always add tests. Please double check before you say that.

[edalzell]

Love this one, thanks @ralphjsmit!

[tillkruss]

This should be the the Laravel default.

[ralphjsmit]

@tillkruss Agree! You could PR it though, perhaps Taylor is open to making it the default in 9.x or 10.x. 👊

[taylorotwell]

@ralphjsmit this PR actually doesn't work for simple cases like:

$user = new User(['unfillable' => 'foo']);

[taylorotwell]

Attempted fix here: eff2275