Use libraryfolders.vdf to find addtl steam games

* Add `read_library_folders` method to read and parse the
`libraryfolders.vdf` file for additional Steam game libraries
* Add `get_library_config` method to the steam runner file
to execute the `read_library_folders()` method from the steam
config file.
* After parsing the `config.vdf` file for any `BaseInstallFolder_X`
keys, it will now also look for any `path` keys in the
parsed `libraryfolders.vdf` dictionary. This happens before the code
cleans up duplicate entries in the `dirs` array.

lutris/runners/steam.py

@@ -10,7 +10,7 @@ from lutris.runners.runner import Runner
 from lutris.util import linux, system
 from lutris.util.log import logger
 from lutris.util.steam.appmanifest import get_appmanifest_from_appid, get_path_from_appmanifest
-from lutris.util.steam.config import STEAM_DATA_DIRS, get_default_acf, get_steam_dir, read_config
+from lutris.util.steam.config import STEAM_DATA_DIRS, get_default_acf, get_steam_dir, read_config, read_library_folders
 from lutris.util.steam.vdf import to_vdf
 from lutris.util.strings import split_arguments
 
@@ -144,6 +144,10 @@ class steam(Runner):
         """Return the "Steam" part of Steam's config.vdf as a dict."""
         return read_config(self.steam_data_dir)
 
+    def get_library_config(self):
+        """Return the "libraryfolders" part of Steam's libraryfolders.vdf as a dict """
+        return read_library_folders(self.steam_data_dir)
+
     @property
     def game_path(self):
         if not self.appid:
@@ -235,6 +239,21 @@ class steam(Runner):
                     dirs.append(path)
                 i += 1
 
+        # New Custom dirs
+        if library_config := self.get_library_config():
+            paths = []
+            for entry in library_config.values():
+                if "mounted" in entry:
+                    if entry.get("path") and entry.get("mounted") == "1":
+                        path = system.fix_path_case(entry.get("path") + "/steamapps")
+                        paths.append(path)
+                else:
+                    path = system.fix_path_case(entry.get("path") + "/steamapps")
+                    paths.append(path)
+            for path in paths:
+                if path and os.path.isdir(path):
+                    dirs.append(path)
+
         # Deduplicate directories with the same Device.Inode
         unique_dirs = {}
         for _dir in dirs:

lutris/util/steam/config.py

@@ -141,6 +141,30 @@ def read_config(steam_data_dir):
         logger.error("Steam config %s is empty: %s", config_filename, ex)
 
 
+def read_library_folders(steam_data_dir):
+    """Read the Steam Library Folders config and return it as an object"""
+    def get_entry_case_insensitive(library_dict, path):
+        for key, value in library_dict.items():
+            if key.lower() == path[0].lower():
+                if len(path) <= 1:
+                    return value
+                return get_entry_case_insensitive(library_dict[key], path[1:])
+            raise KeyError(path[0])
+    if not steam_data_dir:
+        return None
+    library_filename = os.path.join(steam_data_dir, "config/libraryfolders.vdf")
+    if not system.path_exists(library_filename):
+        return None
+    with open(library_filename, "r") as steam_library_file:
+        library = vdf_parse(steam_library_file, {})
+        # The contentstatsid key is unused and causes problems when looking for library paths.
+        library["libraryfolders"].pop("contentstatsid")
+    try:
+        return get_entry_case_insensitive(library, ["libraryfolders"])
+    except KeyError as ex:
+        logger.error("Steam libraryfolders %s is empty: %s", library_filename, ex)
+
+
 def get_steamapps_paths():
     from lutris.runners import steam  # pylint: disable=import-outside-toplevel
     return steam.steam().get_steamapps_dirs()