Cache _has_init calls to avoid repeated stats (#2429)

_has_init can end up checking for the presence of the same files
over and over.

For example, when running pylint's import-error checks on a
codebase like yt-dlp, ~43,000 redundant stats were performed prior
to caching.

Closes pylint-dev/pylint#9613.

Author: correctmost

astroid/manager.py

@@ -23,6 +23,7 @@
 from astroid.modutils import (
     NoSourceFile,
     _cache_normalize_path_,
+    _has_init,
     file_info_from_modpath,
     get_source_file,
     is_module_name_part_of_extension_package_whitelist,
@@ -469,6 +470,7 @@ def clear_cache(self) -> None:
         for lru_cache in (
             LookupMixIn.lookup,
             _cache_normalize_path_,
+            _has_init,
             util.is_namespace,
             ObjectModel.attributes,
             ClassDef._metaclass_lookup_attribute,

astroid/modutils.py

@@ -670,6 +670,7 @@ def _is_python_file(filename: str) -> bool:
     return filename.endswith((".py", ".pyi", ".so", ".pyd", ".pyw"))
 
 
+@lru_cache(maxsize=1024)
 def _has_init(directory: str) -> str | None:
     """If the given directory has a valid __init__ file, return its path,
     else return None.