[7.x] FindOrFail being passed null as value on string key returns a model with empty string as key

[RikSomers]

• Laravel Version: 7.26.0
• PHP Version: 7.3.3
• Database Driver & Version: SQL Server 2017

Description:

When you try to fetch a model with a string key with findOrFail, if you pass the value null, it can find a row where the key is an empty string, where previously it would fail to find the model.

Steps To Reproduce:

Given that you have a model with a string primary key:

 public $incrementing = false;

 protected $keyType = 'string';

And given that you have a row in the database with the key being " " (so an empty string).

When you try to fetch the model by passing null to findOrFail

Model::findOrFail(null)

You will receive the row in the database with the empty string.

This has been broken since #33930, as it has been working before on laravel 7.25.0 when this method hadn't been changed.

Our Case

We use a database (not in our control how the database is structured) that has default "empty" keys so it can create cyclic relationships. So for example, a user needs to be created by a user, but for that you need there to be a default user that's created by itself. So this database gets created with foreign key checks disabled, and then afterwards they enable them, because there is now a default "empty" user.

Currently, what we are doing in several places in our code is fetching something based on a value passed in a form request. So what our code currently is doing, is basically the following:

$documentGrp = DocumentGrp::findOrFail(request('doc-grp-code'));

// some other code

$documentGrp->documents()->map(function ($document) {
   // do something with the documents
});

What happened previously was that the findOrFail would fail, because it tried to fetch a model where the key was the literal null value. Since #33930 however, it will typecast the null to a string, so then in turn it will try to find a model that has an empty string as its key.

So instead of executing

Model::findOrFail(null)

In essence, you would be executing the following:

Model::findOrFail('');

Which to me is a completely different findOrFail being executed.

[driesvints]

Thanks for the detailed report. I'll look into this.

[driesvints]

Sent in a fix for this: #34031

[RikSomers]

Thanks for the quick response!