[8.x] Fix getDirty method when using class castables (e.g. As(Encrypted)ArrayObject/As(Encrypted)Collection)

[gdebrauwer]

What is the issue?

In MySQL, a JSON column adds spaces between the JSON keys and the JSON values, even when you explicitly try to save it without spaces.

// If you try to save this in a MySQL json column:
{"foo":"bar"}
// Then MySQL will save it like this:
{"foo": "bar"}

This causes an issue when using the AsArrayObject casting class on a JSON attribute. Currently, the originalIsEquivalent method (used by getDirty method) does nothing special when an attribute uses a class castable. This means that it will do a strict string comparison between the original and the new value, which will result in a false because of the spaces in the original value. This causes a lot of unnecessary update queries because Eloquent thinks a model contains changes.

'{"foo": "bar"}' !== '{"foo":"bar"}'

How to fix it?

To fix this, we need to cast the original attribute using the class castable before comparing the two values. This casting is done in the originalIsEquivalent method itself. It does not use the castAttribute because that causes issues with the classCastCache (which caches only based key instead of key-value combination).

I also updated the get methods of the As(Encrypted)ArrayObject and As(Encrypted)Collection casts. The get method currently uses the value in the $attributes array, while it should use the provided $value.

[GrahamCampbell]

Please un-mark this as draft, when ready for review.

[taylorotwell]

A cast test is failing.

[driesvints]

@gdebrauwer rebase again and the tests should pass now.

[taylorotwell]

Honestly not sure I want to tinker with casting comparisons on a patch release.

I also don't think this is a full proof way for solving casting comparisons on custom casts. What if the get returns an object like Address that is made of multiple values from $attributes like street_line_1 and street_line_2, etc. Since you're passing in the "current" attributes the created object will not be an accurate reflection of the original attributes?