Give the ability to interrupt the file uploading on OnFileManagerBeforeUpload event

[GulomovCreative]

Summary

We have a plugin that should fired the "OnFileManagerBeforeUpload" event:

if(condition) {
    $source->addError('path', 'Some error text');
}

We see our custom error text, but file will uploaded:

If we try to use exit, the file won't upload, but we don't see our error text:

if(condition) {
    $source->addError('path', 'Some error text');
    exit;
}

Notes

It would be nice if it would be possible to interrupt the file upload.

Environment

MODX Revolution 2.6.5-pl

[GulomovCreative]

Need to set error to true, thanks to @pavel-one

$modx->event->params['file']['error'] = 1;