fix(core): prevent skipped files from being allocated and written to disk

Two related issues when setting file priorities to Skip (0):

1. file_priorities were not included in add_torrent_params, so libtorrent
   allocated storage for all files (including skipped ones) before
   set_file_priorities() was called post-add. Now passed at add time for
   torrents with metadata; magnets continue to use on_metadata_received().

2. Boundary pieces needed by adjacent wanted files leave corrupt partial
   data on disk for newly-skipped files. set_file_priorities() now removes
   any existing non-empty file when its priority is first set to 0.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: flound1129

deluge/core/torrent.py

@@ -535,15 +535,32 @@ def set_file_priorities(self, file_priorities):
             log.debug('Unable to set new file priorities.')
             file_priorities = self.handle.get_file_priorities()
 
-        if 0 in self.options['file_priorities']:
-            # Previously marked a file 'skip' so check for any 0's now >0.
-            for index, priority in enumerate(self.options['file_priorities']):
+        prev_priorities = self.options['file_priorities']
+        if prev_priorities:
+            for index, priority in enumerate(prev_priorities):
                 if priority == 0 and file_priorities[index] > 0:
                     # Changed priority from skip to download so update state.
                     self.is_finished = False
                     self.update_state()
                     break
 
+        # Remove any partial files that were written for files now being skipped.
+        # Boundary pieces for adjacent wanted files can leave corrupt partial data
+        # on disk for skipped files; delete them so they don't appear as corrupt files.
+        if 0 in file_priorities:
+            ti = self.torrent_info
+            save_path = self.options['download_location']
+            for index, priority in enumerate(file_priorities):
+                was_not_skipped = not prev_priorities or prev_priorities[index] != 0
+                if priority == 0 and was_not_skipped:
+                    file_path = os.path.join(save_path, ti.file_at(index).path)
+                    if os.path.exists(file_path) and os.path.getsize(file_path) > 0:
+                        log.debug('Removing partial skipped file: %s', file_path)
+                        try:
+                            os.remove(file_path)
+                        except OSError as ex:
+                            log.warning('Unable to remove skipped file %s: %s', file_path, ex)
+
         # Store the priorities.
         self.options['file_priorities'] = file_priorities
 

deluge/core/torrentmanager.py

@@ -477,6 +477,13 @@ def _build_torrent_params(
             add_torrent_params['name'] = options['name']
         if options['pre_allocate_storage']:
             add_torrent_params['storage_mode'] = lt.storage_mode_t.storage_mode_allocate
+        # Pass file priorities at add time so libtorrent's storage layer respects them
+        # before any space is allocated or pieces are queued. Without this, libtorrent
+        # allocates storage for all files (including skipped ones) and may begin
+        # downloading them before set_file_priorities() is called post-add.
+        # Only set for torrents with metadata; magnets get priorities via on_metadata_received().
+        if options['file_priorities'] and torrent_info:
+            add_torrent_params['file_priorities'] = options['file_priorities']
         if resume_data:
             add_torrent_params['resume_data'] = resume_data