[5.4] Set data key when testing file uploads in nested array

[RDelorier]

Fix a bug that causes data keys to be overridden when testing a nested file upload array.

Example of bug in action:

routes/web.php

Route::post('test', function () {
    Validator::make(request()->all(), [
        'foo' => 'required'
    ])->validate();
});

tests/Feature/ExampleTest.php

<?php

namespace Tests\Feature;

use Tests\TestCase;
use Illuminate\Http\UploadedFile;

class ExampleTest extends TestCase
{
    public function testExample()
    {
        $this->postJson('test', [
            'foo' => 'bar',
            'images' => [UploadedFile::fake()->image('image.jpg')]
        ])->assertStatus(200);
    }
}

Test result:

Expected status code 200 but received 422.
Failed asserting that false is true.

This pr sets the value in the data which fixes the bug.

fixes #18671

[themsaid]

This is wrong, using unset($data[$key]) here will unset every single key with a value of type array, even if the field is not an array of files.

[themsaid]

Replace this with $data[$key] = $value;, I think it'll fix your issue.

[RDelorier]

Woops, good catch @themsaid