Float attribute: Change null to 0 doesn't save to DB - HasAttributes::originalIsEquivalent() bug

[sshead]

• Laravel Version: 7.18.0
• PHP Version: 7.4.6
• Database Driver & Version: MySQL 5.7

Description:

It seems recent changes to fix originalIsEquivalent for floats in \Illuminate\Database\Eloquent\Concerns\HasAttributes have broken the ability to change null to 0 with a float attribute.

That is, if you do $model->attr = 0 then $model->save(), the change is not saved to the database, because originalIsEquivalent('attr') returns true (so $model->getDirty() returns []).

I think it started with #33259, but the most recent version seems to be #33322.

PS: The first two tests in originalIsEquivalent() are:

if ($attribute === $original) {
    return true;
} elseif (is_null($attribute)) {
    return false;
}

I'm wondering if you could simply change the second of these to elseif (is_null($attribute) || is_null($original))? Is there any case in which the original can be null and the new value non-null, but they are considered equivalent?

PPS: I'm a very part-time volunteer dev - I've almost never done this sort of thing, so hope I'm doing it right...

Steps To Reproduce:

Here's the result of my tinkering (some irrelevant output lines omitted):

>>> $result = App\Models\Result::first();
=> App\Models\Result {#4410
     id: 1,
     mark_0: 15.0,
     mark_1: 75.0,
     mark_2: null,
   }
>>> $result->mark_2 = 0;
=> 0
>>> $result->getDirty();
=> []
>>> $result->save();
=> true
>>> $result->fresh();
=> App\Models\Result {#4394
     id: 1,
     mark_0: 15.0,
     mark_1: 75.0,
     mark_2: null,
   }

And here's the same test run on an earlier version (7.12) of the framework:

>>> $result = App\Models\Result::first();
=> App\Models\Result {#4387
     id: 1,
     mark_0: 15.0,
     mark_1: 75.0,
     mark_2: null,
   }
>>> $result->mark_2 = 0;
=> 0
>>> $result->getDirty();
=> [
     "mark_2" => 0,
   ]
>>> $result->save();
=> true
>>> $result->fresh();
=> App\Models\Result {#4400
     id: 1,
     mark_0: 15.0,
     mark_1: 75.0,
     mark_2: 0.0,
   }

[driesvints]

Did #33421 fix this?

[driesvints]

Try requiring 7.x-dev as it's unreleased atm.

[sshead]

Sorry, missed that - though is that merged to 7.x? I tried 7.x-dev and it's still the old version.

[sshead]

Oh - seems there are other differences between 6.x and 7.x, so implementation would be slightly different ($attribute not $current).