Update typing.Self import to be backward compatible

typing.Self was introduced in 3.11. Use a custom TypeVar for older
releases.

astroplan/constraints.py

@@ -9,7 +9,7 @@
 
 # Standard library
 from abc import ABCMeta, abstractmethod
-from typing import Optional, Self, Sequence, Union
+from typing import Optional, Sequence, TypeVar, Union, _SpecialForm
 import datetime
 import time
 import warnings
@@ -28,11 +28,13 @@
 # Package
 from .moon import moon_illumination
 from .periodic import EclipsingSystem, PeriodicEvent
-from .utils import time_grid_from_range
+from .utils import time_grid_from_range, _import_typing_self_compat
 from .observer import Observer
 from .target import get_skycoord, FixedTarget
 from .exceptions import MissingConstraintWarning
 
+Self: Union[TypeVar, _SpecialForm] = _import_typing_self_compat()
+
 __all__ = ["AltitudeConstraint", "AirmassConstraint", "AtNightConstraint",
            "is_observable", "is_always_observable", "time_grid_from_range",
            "GalacticLatitudeConstraint", "SunSeparationConstraint",

astroplan/observer.py

@@ -5,7 +5,7 @@
 
 # Standard library
 import sys
-from typing import Any, Callable, Optional, Self, Sequence, Union
+from typing import Any, Callable, Optional, Sequence, Union
 import datetime
 import warnings
 
@@ -23,6 +23,9 @@
 from .exceptions import TargetNeverUpWarning, TargetAlwaysUpWarning
 from .moon import moon_illumination, moon_phase_angle
 from .target import get_skycoord, SunFlag, MoonFlag, FixedTarget
+from .utils import _import_typing_self_compat
+
+Self = _import_typing_self_compat()
 
 
 __all__ = ["Observer"]

astroplan/scheduling.py

@@ -7,7 +7,7 @@
 
 import copy
 from abc import ABCMeta, abstractmethod
-from typing import Optional, Self, Sequence, Union
+from typing import Optional, Sequence, Union
 
 import numpy as np
 from astropy import units as u
@@ -18,7 +18,9 @@
 from .constraints import AltitudeConstraint, Constraint
 from .observer import Observer
 from .target import FixedTarget, get_skycoord
-from .utils import stride_array, time_grid_from_range
+from .utils import stride_array, time_grid_from_range, _import_typing_self_compat
+
+Self = _import_typing_self_compat()
 
 __all__ = ['ObservingBlock', 'TransitionBlock', 'Schedule', 'Slot',
            'Scheduler', 'SequentialScheduler', 'PriorityScheduler',

astroplan/target.py

@@ -1,15 +1,18 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
-from __future__ import (absolute_import, division, print_function,
-                        unicode_literals)
+from __future__ import absolute_import, division, print_function, unicode_literals
 
 # Standard library
 from abc import ABCMeta
-from typing import Optional, Self, Union
+from typing import Optional, Union
 
 # Third-party
 import astropy.units as u
+from astropy.coordinates import ICRS, SkyCoord, UnitSphericalRepresentation
 from astropy.units import Quantity
-from astropy.coordinates import SkyCoord, ICRS, UnitSphericalRepresentation
+
+from .utils import _import_typing_self_compat
+
+Self = _import_typing_self_compat()
 
 __all__ = ["Target", "FixedTarget", "NonFixedTarget"]
 

astroplan/utils.py

@@ -4,7 +4,7 @@
 
 # Standard library
 import warnings
-from typing import Union
+from typing import Union, _SpecialForm, TypeVar
 import os
 
 # Third-party
@@ -21,7 +21,7 @@
 
 __all__ = ["download_IERS_A",
            "time_grid_from_range", "_set_mpl_style_sheet",
-           "stride_array"]
+           "stride_array", "_import_typing_self_compat"]
 
 IERS_A_WARNING = ("For best precision (on the order of arcseconds), you must "
                   "download an up-to-date IERS Bulletin A table. To do so, run:"
@@ -259,3 +259,12 @@ def _open_shelve(shelffn: Union[str, os.PathLike], withclosing: bool = False) ->
         return contextlib.closing(shelf)
     else:
         return shelf
+
+
+def _import_typing_self_compat() -> Union[_SpecialForm, TypeVar]:
+    # TODO: Remove when no support for Python<3.11
+    try:
+        from typing import Self
+    except ImportError:
+        Self = TypeVar("Self")
+    return Self