TYP: fix type-check incompatibilities with matplotlib 3.8

yt/visualization/_handlers.py

@@ -1,7 +1,7 @@
 import sys
 import weakref
 from numbers import Real
-from typing import Any, Literal, Optional, Union
+from typing import TYPE_CHECKING, Any, Literal, Optional, Union
 
 import matplotlib as mpl
 import numpy as np
@@ -18,6 +18,24 @@
 else:
     from typing_extensions import TypeAlias
 
+if TYPE_CHECKING:
+    # RGBColorType, RGBAColorType and ColorType are backported from matplotlib 3.8.0
+    RGBColorType = Union[tuple[float, float, float], str]
+    RGBAColorType = Union[
+        str,  # "none" or "#RRGGBBAA"/"#RGBA" hex strings
+        tuple[float, float, float, float],
+        # 2 tuple (color, alpha) representations, not infinitely recursive
+        # RGBColorType includes the (str, float) tuple, even for RGBA strings
+        tuple[RGBColorType, float],
+        # (4-tuple, float) is odd, but accepted as the outer float overriding A of 4-tuple
+        tuple[tuple[float, float, float, float], float],
+    ]
+
+    ColorType = Union[RGBColorType, RGBAColorType]
+
+    # this type alias is unique to the present module
+    ColormapInput: TypeAlias = Union[Colormap, str, None]
+
 
 class NormHandler:
     """
@@ -398,16 +416,6 @@ def get_minmax(data):
         return linthresh
 
 
-BackgroundColor: TypeAlias = Union[
-    tuple[float, float, float, float],
-    # np.ndarray is only runtime-subscribtable since numpy 1.22
-    "np.ndarray[Any, Any]",
-    str,
-    None,
-]
-ColormapInput: TypeAlias = Union[Colormap, str, None]
-
-
 class ColorbarHandler:
     __slots__ = ("_draw_cbar", "_draw_minorticks", "_cmap", "_background_color")
 
@@ -423,7 +431,7 @@ def __init__(
         self._draw_minorticks = draw_minorticks
         self._cmap: Optional[Colormap] = None
         self._set_cmap(cmap)
-        self._background_color: BackgroundColor = background_color
+        self._background_color: Optional["ColorType"] = background_color
 
     @property
     def draw_cbar(self) -> bool:
@@ -465,7 +473,7 @@ def _set_cmap(self, newval: ColormapInput) -> None:
             self._cmap = newval
         elif isinstance(newval, str):
             self._cmap = mpl.colormaps[newval]
-        elif is_sequence(newval):
+        elif is_sequence(newval):  # type: ignore[unreachable]
             # tuple colormaps are from palettable (or brewer2mpl)
             self._cmap = get_brewer_cmap(newval)
         else:
@@ -475,14 +483,11 @@ def _set_cmap(self, newval: ColormapInput) -> None:
             )
 
     @property
-    def background_color(self) -> BackgroundColor:
+    def background_color(self) -> "ColorType":
         return self._background_color or "white"
 
     @background_color.setter
-    def background_color(self, newval: BackgroundColor) -> None:
-        # not attempting to constrain types here because
-        # down the line it really depends on matplotlib.axes.Axes.set_faceolor
-        # which is very type-flexibile
+    def background_color(self, newval: Optional["ColorType"]) -> None:
         if newval is None:
             self._background_color = self.cmap(0)
         else:

yt/visualization/base_plot_types.py

@@ -2,7 +2,6 @@
 import warnings
 from abc import ABC
 from io import BytesIO
-from types import FunctionType
 from typing import TYPE_CHECKING, Optional, TypedDict, Union
 
 import matplotlib
@@ -37,6 +36,7 @@
     from matplotlib.axes import Axes
     from matplotlib.axis import Axis
     from matplotlib.figure import Figure
+    from matplotlib.transforms import Transform
 
     class FormatKwargs(TypedDict):
         style: Literal["scientific"]
@@ -249,7 +249,7 @@ def __init__(
     ):
         """Initialize ImagePlotMPL class object"""
 
-        self._transform: Optional[FunctionType]
+        self._transform: Optional["Transform"]
         setdefaultattr(self, "_transform", None)
 
         self.colorbar_handler = colorbar_handler