MIME detection fails when verifying a file with a remote URI

Patch applies successfully and works with and without stage_file_proxy

1. +++ b/src/MimeDetectService.php
   @@ -87,10 +87,21 @@ class MimeDetectService implements MimeDetectServiceInterface {
   +      if (\Drupal::moduleHandler()->moduleExists('stage_file_proxy')) {
   +        $server = \Drupal::config('stage_file_proxy.settings')->get('origin');
   +        $fetch_manager = \Drupal::service('stage_file_proxy.fetch_manager');
   

   Dependency injection → should be used here to make use of the module handler, config manager and Stage File Proxy fetch manager.

2. +++ b/src/MimeDetectService.php
   @@ -87,10 +87,21 @@ class MimeDetectService implements MimeDetectServiceInterface {
   +        $file_path = implode('/', [$server, $file_dir, $relative_path]);
   

   It seems that path to file is composed using the remote server name, which ends in a non local file path (eg.: http://www.example.com/sites/default/files/image.jpg). The following mime detection method (file UNIX command) is unable to manage remote URLs, it only works with local files, so the file itself should be retrieved.

I think that there is no point of checking remote files since they should be already checked on their environment. A better approach here would be just to skip non-local files.

I think that there is no point of checking remote files since they should be already checked on their environment. A better approach here would be just to skip non-local files.

Good point. I've taken this approach, by skipping remote files in hook_file_validate.
Hiding the patches, latest code is in the MR.