issue_comments

It's not pretty, but this seems to work, on top of the most recent commit 2191fbc:

```diff diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml index 232dbec3..3b490dcc 100644 --- a/.pre-commit-config.yaml +++ b/.pre-commit-config.yaml @@ -43,6 +43,7 @@ repos: types-pytz, # Dependencies that are typed numpy, + typing-extensions==3.10.0.0, ] # run this occasionally, ref discussion https://github.com/pydata/xarray/pull/3194 # - repo: https://github.com/asottile/pyupgrade diff --git a/xarray/core/utils.py b/xarray/core/utils.py index 1f2dfb5c..a139d2ef 100644 --- a/xarray/core/utils.py +++ b/xarray/core/utils.py @@ -10,6 +10,7 @@ import warnings from enum import Enum from typing import ( + TYPE_CHECKING, Any, Callable, Collection, @@ -32,7 +33,6 @@ import numpy as np import pandas as pd

- K = TypeVar("K") V = TypeVar("V") T = TypeVar("T") @@ -307,19 +307,29 @@ def _is_scalar(value, include_0d): )

+# See GH5624, this is a convoluted way to allow type-checking to use TypeGuard without +# requiring typing_extensions as a required dependency to run the code (it is required +# to type-check). try: if sys.version_info >= (3, 10): from typing import TypeGuard else: from typing_extensions import TypeGuard except ImportError: - def is_scalar(value: Any, include_0d: bool = True) -> bool: - """Whether to treat a value as a scalar. + if TYPE_CHECKING: + raise + else: + + def is_scalar(value: Any, include_0d: bool = True) -> bool: + """Whether to treat a value as a scalar. + + Any non-iterable, string, or 0-D array + """ + return _is_scalar(value, include_0d) +

• Any non-iterable, string, or 0-D array
• """
• return _is_scalar(value, include_0d) else: + def is_scalar(value: Any, include_0d: bool = True) -> TypeGuard[Hashable]: """Whether to treat a value as a scalar.

```

It works with or without the edit to .pre-commit-config.yaml

@shoyer want me to add it on and merge?

Sorry to be late to the party here — I've been less in the flow of xarray for the past week.

How strongly do you feel about not having this as a dependency @shoyer ? I hadn't thought of it as controversial given it's a "official" python package, but without much confidence so happy to defer.

A few options: - Revert TypeGuard (when would we add it back — when typing-extensions has more track record? When 3.10 is our minimum version?) - Have typing-extensions be optional and add # type: ignore comments. Not sure how many would be required though. - Have typing-extensions be optional but raise an error on if TYPE_CHECKING if it's not installed — i.e. type checking will fail without it, but running xarray would be fine. - Make it a required dependency

If we can get a good error message, I would vote for requiring it for type-checking. If it silently swallows the error and doesn't type check, then I'd probably vote for reverting TypeGuard or making typing-extensions required.