fix: Fix regression with LRU cached method

Issue #549: #549

src/mkdocstrings/plugin.py

@@ -231,7 +231,7 @@ def on_config(self, config: Config, **kwargs: Any) -> Config:  # noqa: ARG002
             inv_loader = futures.ThreadPoolExecutor(4)
             for handler_name, import_item in to_import:
                 future = inv_loader.submit(
-                    self._load_inventory,
+                    self._load_inventory,  # type: ignore[misc]
                     self.get_handler(handler_name).load_inventory,
                     **import_item,
                 )
@@ -330,9 +330,9 @@ def get_handler(self, handler_name: str) -> BaseHandler:
         return self.handlers.get_handler(handler_name)
 
     @classmethod
-    @functools.lru_cache(maxsize=None)
     # lru_cache does not allow mutable arguments such lists, but that is what we load from YAML config.
     @list_to_tuple
+    @functools.lru_cache(maxsize=None)
     def _load_inventory(cls, loader: InventoryLoaderType, url: str, **kwargs: Any) -> Mapping[str, str]:
         """Download and process inventory files using a handler.
 

tests/test_inventory.py

@@ -5,13 +5,16 @@
 import sys
 from io import BytesIO
 from os.path import join
+from typing import TYPE_CHECKING
 
 import pytest
 from mkdocs.commands.build import build
 from mkdocs.config import load_config
 
 from mkdocstrings.inventory import Inventory, InventoryItem
 
+if TYPE_CHECKING:
+    from mkdocstrings.plugin import MkdocstringsPlugin
 sphinx = pytest.importorskip("sphinx.util.inventory", reason="Sphinx is not installed")
 
 
@@ -55,3 +58,12 @@ def test_sphinx_load_mkdocstrings_inventory_file() -> None:
 
     for item in own_inv.values():
         assert item.name in sphinx_inv[f"{item.domain}:{item.role}"]
+
+
+def test_load_inventory(plugin: MkdocstringsPlugin) -> None:
+    """Test the plugin inventory loading method.
+
+    Parameters:
+        plugin: A mkdocstrings plugin instance.
+    """
+    plugin._load_inventory(loader=lambda *args, **kwargs: (), url="https://example.com", domains=["a", "b"])  # type: ignore[misc,arg-type]