fix: tolerate scanpy 1.13 relocation of internal plotting helpers

scanpy 1.13 moved the default palettes and several private plotting
helpers from scanpy.plotting.{palettes,_tools,_utils} to
scanpy.plotting.legacy.*, breaking `import spatialdata_plot` on
pre-release scanpy (every test errored at conftest collection).

Add a single _scanpy_compat module that imports each symbol from the new
path and falls back to the old one, and route all call sites through it:

- default_20 / default_28 / default_102  (_palette.py, _color.py, utils.py)
- _add_categorical_legend                (render.py, utils.py)
- add_colors_for_categorical_sample_annotation  (_color.py)

Values and behaviour are unchanged (the palettes hash identically across
versions); this only confines the reliance on scanpy internals to one
version-tolerant module. scanpy._settings / scanpy.settings are unaffected.

Author: timtreis

src/spatialdata_plot/pl/_color.py

@@ -27,8 +27,6 @@
 from numpy.random import default_rng
 from pandas.api.types import CategoricalDtype, is_bool_dtype, is_numeric_dtype, is_string_dtype
 from pandas.core.arrays.categorical import Categorical
-from scanpy.plotting._utils import add_colors_for_categorical_sample_annotation
-from scanpy.plotting.palettes import default_20, default_28, default_102
 from skimage.color import label2rgb
 from skimage.morphology import erosion, footprint_rectangle
 from skimage.util import map_array
@@ -42,6 +40,12 @@
 )
 
 from spatialdata_plot._logging import logger
+from spatialdata_plot.pl._scanpy_compat import (
+    add_colors_for_categorical_sample_annotation,
+    default_20,
+    default_28,
+    default_102,
+)
 from spatialdata_plot.pl.render_params import (
     CmapParams,
     Color,

src/spatialdata_plot/pl/_palette.py

@@ -20,7 +20,8 @@
 import pandas as pd
 from matplotlib.colors import ListedColormap, to_hex, to_rgb
 from matplotlib.pyplot import colormaps as mpl_colormaps
-from scanpy.plotting.palettes import default_20, default_28, default_102
+
+from spatialdata_plot.pl._scanpy_compat import default_20, default_28, default_102
 
 if TYPE_CHECKING:
     import spatialdata as sd

src/spatialdata_plot/pl/_scanpy_compat.py

@@ -0,0 +1,31 @@
+"""Version-tolerant access to scanpy internals used by spatialdata-plot.
+
+scanpy 1.13 relocated the default palettes and several private plotting helpers from
+``scanpy.plotting.{palettes,_tools,_utils}`` to ``scanpy.plotting.legacy.*``. The values and
+behaviour are unchanged, so we import from whichever path the installed scanpy exposes and
+re-export from a single place. This keeps spatialdata-plot working on scanpy both < and >= 1.13
+and confines the reliance on scanpy internals to one module.
+"""
+
+try:  # scanpy >= 1.13
+    from scanpy.plotting.legacy.palettes import default_20, default_28, default_102
+except ImportError:  # scanpy < 1.13
+    from scanpy.plotting.palettes import default_20, default_28, default_102
+
+try:  # scanpy >= 1.13
+    from scanpy.plotting.legacy._tools.scatterplots import _add_categorical_legend
+except ImportError:  # scanpy < 1.13
+    from scanpy.plotting._tools.scatterplots import _add_categorical_legend
+
+try:  # scanpy >= 1.13
+    from scanpy.plotting.legacy._utils import add_colors_for_categorical_sample_annotation
+except ImportError:  # scanpy < 1.13
+    from scanpy.plotting._utils import add_colors_for_categorical_sample_annotation
+
+__all__ = [
+    "_add_categorical_legend",
+    "add_colors_for_categorical_sample_annotation",
+    "default_20",
+    "default_28",
+    "default_102",
+]

src/spatialdata_plot/pl/render.py

@@ -21,7 +21,6 @@
 from matplotlib.cm import ScalarMappable
 from matplotlib.colors import BoundaryNorm, Colormap, ListedColormap, Normalize, to_rgba_array
 from scanpy._settings import settings as sc_settings
-from scanpy.plotting._tools.scatterplots import _add_categorical_legend
 from spatialdata import get_extent, get_values
 from spatialdata.models import PointsModel, ShapesModel, get_table_keys
 from spatialdata.transformations import set_transformation
@@ -60,6 +59,7 @@
     _scale_geometries,
     _validate_polygons,
 )
+from spatialdata_plot.pl._scanpy_compat import _add_categorical_legend
 from spatialdata_plot.pl._validate import (
     _check_obs_var_shadow,
 )

src/spatialdata_plot/pl/utils.py

@@ -31,8 +31,6 @@
 from pandas.api.types import CategoricalDtype, is_numeric_dtype
 from pandas.core.arrays.categorical import Categorical
 from scanpy import settings
-from scanpy.plotting import palettes
-from scanpy.plotting._tools.scatterplots import _add_categorical_legend
 from spatialdata import (
     SpatialData,
     get_element_annotators,
@@ -57,6 +55,7 @@
 from xarray import DataArray, DataTree
 
 from spatialdata_plot._logging import logger
+from spatialdata_plot.pl._scanpy_compat import _add_categorical_legend, default_102
 from spatialdata_plot.pl.render_params import (
     Color,
     ColorbarSpec,
@@ -451,7 +450,7 @@ def _stack_categorical_legend(
 # A per-entry legend past this many categories is unreadable, and scanpy builds it in O(categories^2)
 # (one autoscaling artist each), dominating the render — so skip it with a warning. Tied to scanpy's
 # default_102 palette, beyond which its *default* colors also stop being distinguishable (uniform grey).
-_MAX_LEGEND_CATEGORIES = len(palettes.default_102)
+_MAX_LEGEND_CATEGORIES = len(default_102)
 
 
 def _first_color_per_category(source: pd.Categorical, color_vector: Any) -> dict[Any, Any]: