minor symfony#9079 preUpdate Event Listener On Uploaded Imagery (matt9mg)

This PR was submitted for the 4.0 branch but it was squashed and merged into the 2.8 branch instead (closes symfony#9079).

Discussion
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preUpdate Event Listener On Uploaded Imagery

I've noticed a scenario (a bit of an edge case when uploading imagery).

If you have an entity (say a brochure) but you can give it a title and an image and the image title can be updated without the image being updated (the file type is not an UploadedFile but a File on save it'll persist the full file path instead of the desired filename. The above is a safety measure to ensure the above.

Commits
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a4cc43a preUpdate Event Listener On Uploaded Imagery

Author: xabbuh

controller/upload_file.rst

@@ -310,6 +310,7 @@ automatically upload the file when persisting the entity::
     namespace AppBundle\EventListener;
 
     use Symfony\Component\HttpFoundation\File\UploadedFile;
+    use Symfony\Component\HttpFoundation\File\File;
     use Doctrine\ORM\Event\LifecycleEventArgs;
     use Doctrine\ORM\Event\PreUpdateEventArgs;
     use AppBundle\Entity\Product;
@@ -351,6 +352,10 @@ automatically upload the file when persisting the entity::
             if ($file instanceof UploadedFile) {
                 $fileName = $this->uploader->upload($file);
                 $entity->setBrochure($fileName);
+            } elseif ($file instanceof File) {
+                // prevents the full file path being saved on updates
+                // as the path is set on the postLoad listener
+                $entity->setBrochure($file->getFilename());
             }
         }
     }