fixes for os.path.commonpath and os.path.commonprefix (#5363)

stdlib/genericpath.pyi

@@ -1,12 +1,7 @@
 import sys
 from _typeshed import AnyPath
-from typing import AnyStr, Sequence, Text
-
-if sys.version_info >= (3, 0):
-    def commonprefix(m: Sequence[str]) -> str: ...
-
-else:
-    def commonprefix(m: Sequence[AnyStr]) -> AnyStr: ...
+from os.path import commonprefix as commonprefix
+from typing import Text
 
 def exists(path: AnyPath) -> bool: ...
 def isfile(path: Text) -> bool: ...

stdlib/ntpath.pyi

@@ -3,7 +3,8 @@ import sys
 from _typeshed import AnyPath, BytesPath, StrPath
 from genericpath import exists as exists
 from os import PathLike
-from typing import Any, AnyStr, Optional, Sequence, Tuple, TypeVar, overload
+from os.path import commonpath as commonpath, commonprefix as commonprefix, lexists as lexists
+from typing import AnyStr, Optional, Tuple, TypeVar, overload
 
 _T = TypeVar("_T")
 
@@ -57,15 +58,6 @@ def realpath(path: PathLike[AnyStr]) -> AnyStr: ...
 @overload
 def realpath(path: AnyStr) -> AnyStr: ...
 
-# In reality it returns str for sequences of StrPath and bytes for sequences
-# of BytesPath, but mypy does not accept such a signature.
-def commonpath(paths: Sequence[AnyPath]) -> Any: ...
-
-# NOTE: Empty lists results in '' (str) regardless of contained type.
-# So, fall back to Any
-def commonprefix(m: Sequence[AnyPath]) -> Any: ...
-def lexists(path: AnyPath) -> bool: ...
-
 # These return float if os.stat_float_times() == True,
 # but int is a subclass of float.
 def getatime(filename: AnyPath) -> float: ...

stdlib/os/path.pyi

@@ -1,11 +1,10 @@
 import os
 import sys
-from _typeshed import AnyPath, BytesPath, StrPath
+from _typeshed import AnyPath, BytesPath, StrPath, SupportsLessThanT
 from genericpath import exists as exists
 from os import PathLike
-from typing import Any, AnyStr, Optional, Sequence, Tuple, TypeVar, overload
-
-_T = TypeVar("_T")
+from typing import AnyStr, List, Optional, Sequence, Tuple, Union, overload
+from typing_extensions import Literal
 
 # ----- os.path variables -----
 supports_unicode_filenames: bool
@@ -77,14 +76,22 @@ else:
         @overload
         def realpath(filename: AnyStr) -> AnyStr: ...
 
-# In reality it returns str for sequences of StrPath and bytes for sequences
-# of BytesPath, but mypy does not accept such a signature.
-def commonpath(paths: Sequence[AnyPath]) -> Any: ...
+@overload
+def commonpath(paths: Sequence[StrPath]) -> str: ...
+@overload
+def commonpath(paths: Sequence[BytesPath]) -> bytes: ...
 
-# NOTE: Empty lists results in '' (str) regardless of contained type.
-# So, fall back to Any
-def commonprefix(m: Sequence[AnyPath]) -> Any: ...
-def lexists(path: AnyPath) -> bool: ...
+# All overloads can return empty string. Ideally, Literal[""] would be a valid
+# Iterable[T], so that Union[List[T], Literal[""]] could be used as a return
+# type. But because this only works when T is str, we need Sequence[T] instead.
+@overload
+def commonprefix(m: Sequence[StrPath]) -> str: ...
+@overload
+def commonprefix(m: Sequence[BytesPath]) -> Union[bytes, Literal[""]]: ...
+@overload
+def commonprefix(m: Sequence[List[SupportsLessThanT]]) -> Sequence[SupportsLessThanT]: ...
+@overload
+def commonprefix(m: Sequence[Tuple[SupportsLessThanT, ...]]) -> Sequence[SupportsLessThanT]: ...
 
 # These return float if os.stat_float_times() == True,
 # but int is a subclass of float.
@@ -92,6 +99,7 @@ def getatime(filename: AnyPath) -> float: ...
 def getmtime(filename: AnyPath) -> float: ...
 def getctime(filename: AnyPath) -> float: ...
 def getsize(filename: AnyPath) -> int: ...
+def lexists(path: AnyPath) -> bool: ...
 def isabs(s: AnyPath) -> bool: ...
 def isfile(path: AnyPath) -> bool: ...
 def isdir(s: AnyPath) -> bool: ...

stdlib/posixpath.pyi

@@ -3,7 +3,8 @@ import sys
 from _typeshed import AnyPath, BytesPath, StrPath
 from genericpath import exists as exists
 from os import PathLike
-from typing import Any, AnyStr, Optional, Sequence, Tuple, TypeVar, overload
+from os.path import commonpath as commonpath, commonprefix as commonprefix, lexists as lexists
+from typing import AnyStr, Optional, Tuple, TypeVar, overload
 
 _T = TypeVar("_T")
 
@@ -65,15 +66,6 @@ else:
     @overload
     def realpath(filename: AnyStr) -> AnyStr: ...
 
-# In reality it returns str for sequences of StrPath and bytes for sequences
-# of BytesPath, but mypy does not accept such a signature.
-def commonpath(paths: Sequence[AnyPath]) -> Any: ...
-
-# NOTE: Empty lists results in '' (str) regardless of contained type.
-# So, fall back to Any
-def commonprefix(m: Sequence[AnyPath]) -> Any: ...
-def lexists(path: AnyPath) -> bool: ...
-
 # These return float if os.stat_float_times() == True,
 # but int is a subclass of float.
 def getatime(filename: AnyPath) -> float: ...