Laravel Eloquent Model 'getDirty()' behaviour

[algorhythm]

I'm not sure if this is a bug or a misunderstood behaviour. Following happens with using the 'isDirty()' and 'getDirty()' methods in the Eloquent Model class on setting floats:

I have a column 'netPrice' created with migrations:

Schema::table('invoices', function (Blueprint $table) {
    $table->float('net_price', 8, 4)->unsigned()->nullable();
});

Now I have a Model like this:

class Invoice extends Model {
    protected $table = 'invoices';
    protected $casts = ['net_price' => 'float'];
}

Suppose that the Model is filled with e.g. "24.9900" (string) and I fill it with 24.99 (float) then the method getDirty() shows me the column 'net_price'. OK, I understand, that a string is not a float, but the value written in DB is the same. So we do not have to write it to DB, nothing changes. When I call the property $price = $invoice->net_price I got 24.99 (float).

Question

Why is getDirty() not using my specified $casts to compare the values? Doesn't it make sense?

Workaround

I created a workaround in my code: When I fill the property 'net_price' I do it like this:

$invoice->net_price = number_format(24.99, 4); // "24.9900"

and then the Model isn't dirty anymore.

[rkgrep]

Related #8972