Inconsistent accessor attribute name conversion

Laravel Version

11.42.0

PHP Version

8.4.3

Database Driver & Version

No response

Description

Define a custom attribute with a convoluted name using the Attribute syntax:

Example:

protected function foo1Bar(): Attribute
{
    return Attribute::make(
        get: fn () => 'yay',
    );
}

Accessing a custom attribute is internally done by a snake-to-camel case conversion. So this means both foo1_bar and foo_1_bar will yield the expected value.

However, some features in Eloquent do the inverse by calling upon the attribute cache ($getAttributeMutatorCache): a camel-to-snake case conversion. This means that foo1Bar now only translates to foo1_bar, and not anymore to foo_1_bar even though its value would get returned when retrieving it.

echo $model->foo1_bar; // "yay"
$model->append('foo1_bar');
$model->toArray(); // Works fine.

echo $model->foo_1_bar; // "yay"
$model->append('foo_1_bar');
$model->toArray(); // Call to undefined method Model::getFoo1BarAttribute() 

On the contrary, when resorting back to the good old getFoo1BarAttribute() everything works as expected for both foo1_bar and foo_1_bar.

protected function getFoo1BarAttribute()
{
    return 'yay';
}

echo $model->foo1_bar; // "yay"
$model->append('foo1_bar');
$model->toArray(); // Works fine.

echo $model->foo_1_bar; // "yay"
$model->append('foo_1_bar');
$model->toArray(); // Works fine.

So, because of internal two-way case conversions to support the newer attribute syntax some unexpected and disfunctional ambiguity gets introduced.

I think both syntaxes (Attribute vs getXXXAttribute()) should behave equally. But I'm not quite sure how to proceed with this. Should foo_1_bar get blocked for access to prevent this kind of expectations further down the line? Or should it also resolve properly when doing the camel-to-snake conversion? Or...?

Steps To Reproduce

protected function foo1Bar(): Attribute
{
    return Attribute::make(
        get: fn () => 'yay',
    );
}

$model->append('foo_1_bar');
$model->toArray();