Add user detector

[zepfietje]

This PR adds a detector to get the locale from the currently authenticated user, if any.

[ivanvermeyen]

Thanks for your contribution!

Before merging I'd like to make sure we support this Laravel feature:
laravel/framework#44283

Perhaps the attribute can be null by default?

[zepfietje]

Hmm I'm not sure how we should handle that.
Could you explain your suggestion?

[ivanvermeyen]

I was thinking if this is null in the config by default:

'user-attribute' => null,

Then we can check for it to avoid the MissingAttributeException:

 if ($attribute === null || $user === null) {
    return null;
}

[zepfietje]

Isn't it clearer then to not include the detector in the default array?
Though I was really hoping to make this a default out of the box solution.

[ivanvermeyen]

Yeah, I understand.

Another option is perhaps to check if the attribute exists?
Then it can be default and yet not mandatory?

[ivanvermeyen]

Unfortunately Laravel has no hasAttribute() method.
But I think we can do something like this:

if ( ! in_array($attribute, $user->getAttributes())) {
    return null;
}

[zepfietje]

Yeah that should work.
Doesn't it have any performance implications though, for example calling all casts?

[zepfietje]

@ivanvermeyen, we might use $user->getAttributeValue() to prevent the MissingAttributeException?

Just tested, it should work.

[zepfietje]

This PR should be ready now, @ivanvermeyen.

[ivanvermeyen]

getAttributeValue() seems to defer to getAttributes().

https://github.com/laravel/framework/blob/15f419f751474262f3ced85ea4ccce18cbcdae8e/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php#L481-L495

I'm not sure how big of an impact this has on performance, like you stated.
There doesn't seem to be an easy way to check the $attributes property without triggering the exception.

[zepfietje]

Casting only seems to happen for the specific attribute you're accessing.
So performance-wise I don't think this is an issue really.

Edit: actually casting does happen for all attributes I think.

[zepfietje]

Okay, this isn't any less performant than magically accessing properties like $user->locale, as it all uses the same getAttribute() and thus getAttributeValue() methods under the hood.

[ivanvermeyen]

Great, thanks for putting this together 👍
I'll merge and tag a release.

[zepfietje]

Thanks a lot for being so swift and maintaining these awesome packages!