[cli/core/lfs] Add slightly janky lock for installed game data

In order to prevent multiple instances of Legendary mucking with installed game data
acquire a lock as soon as it is required and only release it (implicitly) when
Legendary exits.

This is a bit jank, but should prevent people from messing up their local data by
running two install commands at a time.

EGL sync is technically also affected by this, but in its case we simply skip the
sync/import/export and leave it to the next instance with a lock to do.

legendary/cli.py

@@ -315,7 +315,7 @@ class LegendaryCLI:
 
         print('\nInstalled games:')
         for game in games:
-            if game.install_size == 0:
+            if game.install_size == 0 and self.core.lgd.lock_installed():
                 logger.debug(f'Updating missing size for {game.app_name}')
                 m = self.core.load_manifest(self.core.get_installed_manifest(game.app_name)[0])
                 game.install_size = sum(fm.file_size for fm in m.file_manifest_list.elements)
@@ -472,12 +472,15 @@ class LegendaryCLI:
             logger.info(f'Checking "{igame.title}" ({igame.app_name})')
             # override save path only if app name is specified
             if args.app_name and args.save_path:
+                if not self.core.lgd.lock_installed():
+                    logger.error('Unable to lock install data, cannot modify save path.')
+                    break
                 logger.info(f'Overriding save path with "{args.save_path}"...')
                 igame.save_path = args.save_path
                 self.core.lgd.set_installed_game(igame.app_name, igame)
 
-            # if there is no saved save path, try to get one
+            # if there is no saved save path, try to get one, skip if we cannot get a install data lock
-            if not igame.save_path:
+            if not igame.save_path and self.core.lgd.lock_installed():
                 if args.yes and not args.accept_path:
                     logger.info('Save path for this title has not been set, skipping due to --yes')
                     continue
@@ -796,6 +799,11 @@ class LegendaryCLI:
             subprocess.Popen(command, env=full_env)
 
     def install_game(self, args):
+        if not self.core.lgd.lock_installed():
+            logger.fatal('Failed to acquire installed data lock, only one instance of Legendary may '
+                         'install/import/move applications at a time.')
+            return
+
         args.app_name = self._resolve_aliases(args.app_name)
         if self.core.is_installed(args.app_name):
             igame = self.core.get_installed_game(args.app_name)
@@ -1129,6 +1137,11 @@ class LegendaryCLI:
             logger.info('Automatic installation not available on Linux.')
 
     def uninstall_game(self, args):
+        if not self.core.lgd.lock_installed():
+            logger.fatal('Failed to acquire installed data lock, only one instance of Legendary may '
+                         'install/import/move applications at a time.')
+            return
+
         args.app_name = self._resolve_aliases(args.app_name)
         igame = self.core.get_installed_game(args.app_name)
         if not igame:
@@ -1259,6 +1272,11 @@ class LegendaryCLI:
                 logger.info(f'Run "legendary repair {args.app_name}" to repair your game installation.')
 
     def import_game(self, args):
+        if not self.core.lgd.lock_installed():
+            logger.fatal('Failed to acquire installed data lock, only one instance of Legendary may '
+                         'install/import/move applications at a time.')
+            return
+
         # make sure path is absolute
         args.app_path = os.path.abspath(args.app_path)
         args.app_name = self._resolve_aliases(args.app_name)
@@ -1354,6 +1372,11 @@ class LegendaryCLI:
         logger.info(f'{"DLC" if game.is_dlc else "Game"} "{game.app_title}" has been imported.')
 
     def egs_sync(self, args):
+        if not self.core.lgd.lock_installed():
+            logger.fatal('Failed to acquire installed data lock, only one instance of Legendary may '
+                         'install/import/move applications at a time.')
+            return
+
         if args.unlink:
             logger.info('Unlinking and resetting EGS and LGD sync...')
             self.core.lgd.config.remove_option('Legendary', 'egl_programdata')
@@ -2509,6 +2532,11 @@ class LegendaryCLI:
             logger.info('Saved choices to configuration.')
 
     def move(self, args):
+        if not self.core.lgd.lock_installed():
+            logger.fatal('Failed to acquire installed data lock, only one instance of Legendary may '
+                         'install/import/move applications at a time.')
+            return
+
         app_name = self._resolve_aliases(args.app_name)
         igame = self.core.get_installed_game(app_name, skip_sync=True)
         if not igame:

legendary/core.py

@@ -1749,6 +1749,9 @@ class LegendaryCore:
     def egl_import(self, app_name):
         if not self.asset_valid(app_name):
             raise ValueError(f'To-be-imported game {app_name} not in game asset database!')
+        if not self.lgd.lock_installed():
+            self.log.warning('Could not acquire lock for EGL import')
+            return
 
         self.log.debug(f'Importing "{app_name}" from EGL')
         # load egl json file
@@ -1796,9 +1799,12 @@ class LegendaryCore:
 
         # mark game as installed
         _ = self._install_game(lgd_igame)
-        return
 
     def egl_export(self, app_name):
+        if not self.lgd.lock_installed():
+            self.log.warning('Could not acquire lock for EGL import')
+            return
+
         self.log.debug(f'Exporting "{app_name}" to EGL')
         # load igame/game
         lgd_game = self.get_game(app_name)
@@ -1860,6 +1866,10 @@ class LegendaryCore:
         """
         Sync game installs between Legendary and the Epic Games Launcher
         """
+        if not self.lgd.lock_installed():
+            self.log.warning('Could not acquire lock for EGL sync')
+            return
+
         # read egl json files
         if app_name:
             lgd_igame = self._get_installed_game(app_name)

legendary/lfs/lgndry.py

@@ -9,6 +9,8 @@ from collections import defaultdict
 from pathlib import Path
 from time import time
 
+from filelock import FileLock
+
 from .utils import clean_filename, LockedJSONData
 
 from legendary.models.game import *
@@ -114,6 +116,8 @@ class LGDLFS:
             self.config.set('Legendary', '; Disables the notice about an available update on exit')
             self.config.set('Legendary', 'disable_update_notice', 'false' if is_windows_mac_or_pyi() else 'true')
 
+        self._installed_lock = FileLock(os.path.join(self.path, 'installed.json') + '.lock')
+
         try:
             self._installed = json.load(open(os.path.join(self.path, 'installed.json')))
         except Exception as e:
@@ -293,6 +297,27 @@ class LGDLFS:
                 except Exception as e:
                     self.log.warning(f'Failed to delete file "{f}": {e!r}')
 
+    def lock_installed(self) -> bool:
+        """
+        Locks the install data. We do not care about releasing this lock.
+        If it is acquired by a Legendary instance it should own the lock until it exits.
+        Some operations such as egl sync may be simply skipped if a lock cannot be acquired
+        """
+        if self._installed_lock.is_locked:
+            return True
+
+        try:
+            self._installed_lock.acquire(blocking=False)
+            # reload data in case it has been updated elsewhere
+            try:
+                self._installed = json.load(open(os.path.join(self.path, 'installed.json')))
+            except Exception as e:
+                self.log.debug(f'Failed to load installed game data: {e!r}')
+
+            return True
+        except TimeoutError:
+            return False
+
     def get_installed_game(self, app_name):
         if self._installed is None:
             try: