[5.4] Undocummented breaking change for eloquent relationship foreign key name

[CyrilMazur]

When omitting the foreign key name in the definition of a relationship, like so

    public function profile()
    {
        return $this->belongsTo(Profile::class);
    }

the foreign key name is automatically generated by Laravel, but the way it generates has changed between 5.3 and 5.4.

In 5.3:

$foreignKey = Str::snake($relation).'_id';

(https://github.com/laravel/framework/blob/5.3/src/Illuminate/Database/Eloquent/Model.php#L776)

In 5.4:

$foreignKey = Str::snake($relation).'_'.$instance->getKeyName();

(https://github.com/laravel/framework/blob/5.4/src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php#L112)

This breaks when a table is using a primary key different from "id".

[ntzm]

You can submit a PR for the docs here

[GrahamCampbell]

Thanks for reporting.

[taylorotwell]

Documented.