nitypes: Extract typing backports into a submodule

src/nitypes/_typing.py

@@ -0,0 +1,41 @@
+"""Single source for typing backports to avoid depending on typing_extensions at run time."""
+
+from __future__ import annotations
+
+import sys
+from typing import TYPE_CHECKING
+
+if sys.version_info >= (3, 10):
+    from typing import TypeAlias
+elif TYPE_CHECKING:
+    from typing_extensions import TypeAlias
+else:
+    TypeAlias = None
+
+if sys.version_info >= (3, 11):
+    from typing import Self, assert_type
+elif TYPE_CHECKING:
+    from typing_extensions import Self, assert_type
+else:
+    Self = None
+
+    def assert_type(val, typ, /):  # noqa: D103 - Missing docstring in public function
+        pass
+
+
+if sys.version_info >= (3, 12):
+    from typing import override
+elif TYPE_CHECKING:
+    from typing_extensions import override
+else:
+
+    def override(arg, /):  # noqa: D103 - Missing docstring in public function
+        return arg
+
+
+__all__ = [
+    "assert_type",
+    "override",
+    "Self",
+    "TypeAlias",
+]

src/nitypes/time/_conversion.py

@@ -1,19 +1,14 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 from collections.abc import Callable
 from functools import singledispatch
 from typing import Any, TypeVar, Union, cast
 
 import hightime as ht
 
 from nitypes._exceptions import invalid_arg_type, invalid_requested_type
-
-if sys.version_info >= (3, 10):
-    from typing import TypeAlias
-else:
-    from typing_extensions import TypeAlias
+from nitypes._typing import TypeAlias
 
 _AnyDateTime: TypeAlias = Union[dt.datetime, ht.datetime]
 _TDateTime = TypeVar("_TDateTime", dt.datetime, ht.datetime)

src/nitypes/waveform/_analog_waveform.py

@@ -2,7 +2,13 @@
 
 import sys
 from collections.abc import Sequence
-from typing import Any, Generic, SupportsIndex, TypeVar, overload
+from typing import (
+    Any,
+    Generic,
+    SupportsIndex,
+    TypeVar,
+    overload,
+)
 
 import numpy as np
 import numpy.typing as npt

src/nitypes/waveform/_extended_properties.py

@@ -1,27 +1,18 @@
 from __future__ import annotations
 
 import operator
-import sys
-from typing import MutableMapping, Iterator
+from typing import Iterator, MutableMapping, Union
 
-if sys.version_info >= (3, 10):
-    from typing import TypeAlias
-else:
-    from typing import Union
-    from typing_extensions import TypeAlias
+from nitypes._typing import TypeAlias
 
 # Extended property keys
 CHANNEL_NAME = "NI_ChannelName"
 LINE_NAMES = "NI_LineNames"
 UNIT_DESCRIPTION = "NI_UnitDescription"
 
 
-if sys.version_info >= (3, 10):
-    ExtendedPropertyValue: TypeAlias = bool | float | int | str
-    """An ExtendedPropertyDictionary value."""
-else:
-    ExtendedPropertyValue: TypeAlias = Union[bool, float, int, str]
-    """An ExtendedPropertyDictionary value."""
+ExtendedPropertyValue: TypeAlias = Union[bool, float, int, str]
+"""An ExtendedPropertyDictionary value."""
 
 
 class ExtendedPropertyDictionary(MutableMapping[str, ExtendedPropertyValue]):

src/nitypes/waveform/_timing/_conversion.py

@@ -1,23 +1,18 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 from collections.abc import Callable
 from functools import singledispatch
 from typing import Any, TypeVar, Union, cast
 
 import hightime as ht
 
 from nitypes._exceptions import invalid_arg_type, invalid_requested_type
+from nitypes._typing import TypeAlias
 from nitypes.time._conversion import convert_datetime, convert_timedelta
 from nitypes.waveform._timing._precision import PrecisionTiming
 from nitypes.waveform._timing._standard import Timing
 
-if sys.version_info >= (3, 10):
-    from typing import TypeAlias
-else:
-    from typing_extensions import TypeAlias
-
 _AnyTiming: TypeAlias = Union[Timing, PrecisionTiming]
 _TTiming = TypeVar("_TTiming", Timing, PrecisionTiming)
 

tests/unit/time/test_conversion.py

@@ -1,19 +1,14 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 from typing import Any
 
 import hightime as ht
 import pytest
 
+from nitypes._typing import assert_type
 from nitypes.time import convert_datetime, convert_timedelta
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 ###############################################################################
 # convert_datetime

tests/unit/waveform/_scaling/test_linear.py

@@ -1,19 +1,14 @@
 from __future__ import annotations
 
-import sys
 from typing import SupportsFloat
 
 import numpy as np
 import numpy.typing as npt
 import pytest
 
+from nitypes._typing import assert_type
 from nitypes.waveform import LinearScaleMode
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 @pytest.mark.parametrize(
     "gain, offset",

tests/unit/waveform/_scaling/test_none.py

@@ -1,17 +1,11 @@
 from __future__ import annotations
 
-import sys
-
 import numpy as np
 import numpy.typing as npt
 
+from nitypes._typing import assert_type
 from nitypes.waveform import NO_SCALING, NoneScaleMode
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 def test___no_scaling___type_is_none_scale_mode() -> None:
     assert_type(NO_SCALING, NoneScaleMode)

tests/unit/waveform/_timing/test_conversion.py

@@ -1,18 +1,13 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 
 import hightime as ht
 
+from nitypes._typing import assert_type
 from nitypes.waveform import PrecisionTiming, SampleIntervalMode, Timing
 from nitypes.waveform._timing import convert_timing
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 def test___standard_to_standard___convert_timing___returns_original_object() -> None:
     value_in = Timing.create_with_regular_interval(

tests/unit/waveform/_timing/test_precision.py

@@ -1,19 +1,14 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 from copy import deepcopy
 
 import hightime as ht
 import pytest
 
+from nitypes._typing import assert_type
 from nitypes.waveform import PrecisionTiming, SampleIntervalMode
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 ###############################################################################
 # empty

tests/unit/waveform/_timing/test_standard.py

@@ -1,18 +1,13 @@
 from __future__ import annotations
 
 import datetime as dt
-import sys
 from copy import deepcopy
 
 import pytest
 
+from nitypes._typing import assert_type
 from nitypes.waveform import SampleIntervalMode, Timing
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 ###############################################################################
 # empty

tests/unit/waveform/test_analog_waveform.py

@@ -3,7 +3,6 @@
 import array
 import datetime as dt
 import itertools
-import sys
 import weakref
 from typing import Any, SupportsIndex
 
@@ -12,6 +11,7 @@
 import numpy.typing as npt
 import pytest
 
+from nitypes._typing import assert_type
 from nitypes.waveform import (
     NO_SCALING,
     AnalogWaveform,
@@ -22,11 +22,6 @@
     Timing,
 )
 
-if sys.version_info >= (3, 11):
-    from typing import assert_type
-else:
-    from typing_extensions import assert_type
-
 
 ###############################################################################
 # create