Fix typing of backends

xarray/backends/api.py

@@ -43,6 +43,8 @@
         from dask.delayed import Delayed
     except ImportError:
         Delayed = None  # type: ignore
+    from io import BufferedIOBase
+
     from ..core.types import (
         CombineAttrsOptions,
         CompatOptions,
@@ -366,7 +368,7 @@ def _dataset_from_backend_dataset(
 
 
 def open_dataset(
-    filename_or_obj: str | os.PathLike | AbstractDataStore,
+    filename_or_obj: str | os.PathLike[Any] | BufferedIOBase | AbstractDataStore,
     *,
     engine: T_Engine = None,
     chunks: T_Chunks = None,
@@ -550,7 +552,7 @@ def open_dataset(
 
 
 def open_dataarray(
-    filename_or_obj: str | os.PathLike,
+    filename_or_obj: str | os.PathLike[Any] | BufferedIOBase | AbstractDataStore,
     *,
     engine: T_Engine = None,
     chunks: T_Chunks = None,

xarray/backends/common.py

@@ -4,7 +4,7 @@
 import os
 import time
 import traceback
-from typing import Any
+from typing import TYPE_CHECKING, Any, ClassVar, Iterable
 
 import numpy as np
 
@@ -13,6 +13,9 @@
 from ..core.pycompat import is_duck_dask_array
 from ..core.utils import FrozenDict, NdimSizeLenMixin, is_remote_uri
 
+if TYPE_CHECKING:
+    from io import BufferedIOBase
+
 # Create a logger object, but don't add any handlers. Leave that to user code.
 logger = logging.getLogger(__name__)
 
@@ -371,13 +374,15 @@ class BackendEntrypoint:
       method is not mandatory.
     """
 
+    available: ClassVar[bool] = True
+
     open_dataset_parameters: tuple | None = None
     """list of ``open_dataset`` method parameters"""
 
     def open_dataset(
         self,
-        filename_or_obj: str | os.PathLike,
-        drop_variables: tuple[str] | None = None,
+        filename_or_obj: str | os.PathLike[Any] | BufferedIOBase | AbstractDataStore,
+        drop_variables: str | Iterable[str] | None = None,
         **kwargs: Any,
     ):
         """
@@ -386,7 +391,10 @@ def open_dataset(
 
         raise NotImplementedError
 
-    def guess_can_open(self, filename_or_obj: str | os.PathLike):
+    def guess_can_open(
+        self,
+        filename_or_obj: str | os.PathLike[Any] | BufferedIOBase | AbstractDataStore,
+    ):
         """
         Backend open_dataset method used by Xarray in :py:func:`~xarray.open_dataset`.
         """

xarray/backends/plugins.py

@@ -6,9 +6,16 @@
 import sys
 import warnings
 from importlib.metadata import entry_points
+from typing import TYPE_CHECKING, Any
 
 from .common import BACKEND_ENTRYPOINTS, BackendEntrypoint
 
+if TYPE_CHECKING:
+    import os
+    from io import BufferedIOBase
+
+    from .common import AbstractDataStore
+
 STANDARD_BACKENDS_ORDER = ["netcdf4", "h5netcdf", "scipy"]
 
 
@@ -83,7 +90,7 @@ def sort_backends(backend_entrypoints):
     return ordered_backends_entrypoints
 
 
-def build_engines(entrypoints):
+def build_engines(entrypoints) -> dict[str, BackendEntrypoint]:
     backend_entrypoints = {}
     for backend_name, backend in BACKEND_ENTRYPOINTS.items():
         if backend.available:
@@ -97,7 +104,7 @@ def build_engines(entrypoints):
 
 
 @functools.lru_cache(maxsize=1)
-def list_engines():
+def list_engines() -> dict[str, BackendEntrypoint]:
     # New selection mechanism introduced with Python 3.10. See GH6514.
     if sys.version_info >= (3, 10):
         entrypoints = entry_points(group="xarray.backends")
@@ -106,7 +113,9 @@ def list_engines():
     return build_engines(entrypoints)
 
 
-def guess_engine(store_spec):
+def guess_engine(
+    store_spec: str | os.PathLike[Any] | BufferedIOBase | AbstractDataStore,
+):
     engines = list_engines()
 
     for engine, backend in engines.items():
@@ -155,7 +164,7 @@ def guess_engine(store_spec):
     raise ValueError(error_msg)
 
 
-def get_backend(engine):
+def get_backend(engine: str | type[BackendEntrypoint]) -> BackendEntrypoint:
     """Select open_dataset method based on current engine."""
     if isinstance(engine, str):
         engines = list_engines()

xarray/core/dataset.py

@@ -2167,7 +2167,7 @@ def chunk(
         token: str | None = None,
         lock: bool = False,
         inline_array: bool = False,
-        **chunks_kwargs: Any,
+        **chunks_kwargs: None | int | str | tuple[int, ...],
     ) -> T_Dataset:
         """Coerce all arrays in this dataset into dask arrays with the given
         chunks.

xarray/tests/__init__.py

@@ -203,7 +203,7 @@ def assert_allclose(a, b, check_default_indexes=True, **kwargs):
     xarray.testing._assert_internal_invariants(b, check_default_indexes)
 
 
-def create_test_data(seed=None, add_attrs=True):
+def create_test_data(seed: int | None = None, add_attrs: bool = True) -> Dataset:
     rs = np.random.RandomState(seed)
     _vars = {
         "var1": ["dim1", "dim2"],