Basically trying to do this in a CakePHP 4.5.9 application.

I have a Model called Whitepapers and with I'm trying to validate a file upload. The code for the application has been created with bake initially.

The template file has a field called filename:

<?= $this->Form->create($whitepaper, ['type' => 'file']) ?>

<?= $this->Form->control('filename', ['label' => 'PDF File', 'type' => 'file']) ?>

<?= $this->Form->button(__('Save')) ?>
<?= $this->Form->end() ?>

In my Controller I have the following

public function add()
{
    $whitepaper = $this->Whitepapers->newEmptyEntity();

    if ($this->request->is('post')) {
        $whitepaper = $this->Whitepapers->patchEntity($whitepaper, $this->request->getData());

        // PDF file
        $file = $this->request->getUploadedFiles();

        // Filename stays the same as uploaded by the user.
        $uploadedFilename = $file['filename']->getClientFilename();

        // Filename for saving in DB
        $whitepaper->filename = $uploadedFilename;

        // ...
    }
 }

My intentions are:

1. To have the file available to upload into cloud storage, which is what $file represents. Subsequent code does this and works correctly.
2. Save the name of the corresponding file in the database in the whitepapers table in a column called filename.
3. Perform validation such that there must be a file uploaded, it is a PDF, and is 10 MB or under.

The code I have in the Model looks like this, which is based off the linked article.

// src/Model/Table/WhitepapersTable.php
class WhitepapersTable extends Table
{
    $validator
        ->scalar('filename')
        ->maxLength('filename', 255)
        ->requirePresence('filename', 'create')
        ->notEmptyFile('filename');

    $validator->uploadedFile('filename', [
        'types' => [
            'application/pdf',
        ],
        'maxSize' => 10 * 1024 * 1024, // 10 MB
    ]);
}

This doesn't work. It will let me upload any file, of any size.

I'm not sure if filename is correct - on the line $validator->uploadedFile('filename') - since that seemingly represents both a column in the database (i.e. the filename) but somehow also the uploaded file itself?

I've cleared all the files in tmp/cache/* to make sure the Model isn't being cached.

What am I doing wrong?