fix(labels): restore render float-dtype guard for spatialdata <0.8 (#751)

Author: timtreis

src/spatialdata_plot/pl/render.py

@@ -2189,9 +2189,15 @@ def _render_labels(
             is_label=True,
         )
 
-    # Label dtype is validated upstream: spatialdata rejects non-integer label rasters at the model
-    # boundary (parse / SpatialData construction / __setitem__), so a validly built element always
-    # reaches here with an integer dtype. No local guard needed (see #606, resolved upstream).
+    # spatialdata >= 0.8 rejects non-integer label rasters at the model boundary, but the library
+    # still supports spatialdata >= 0.3, where float labels parse fine and would otherwise crash
+    # deep in skimage with a cryptic TypeError (#606). Keep a clear render-time guard for that range.
+    if np.issubdtype(label.dtype, np.floating):
+        raise ValueError(
+            f"Label element '{element}' has dtype {label.dtype}. Label arrays must use an "
+            f"integer dtype (e.g. int32 or uint16). Cast before plotting, e.g.:\n"
+            f"    sdata['{element}'] = sdata['{element}'].astype('int32')"
+        )
 
     # rasterize spatial image if necessary to speed up performance
     if rasterize:

tests/_images/Shapes_can_plot_queried_with_annotation_despite_random_shuffling.png

@@ -719,6 +719,24 @@ def test_render_labels_lognorm_with_zeros_does_not_crash(sdata_blobs: SpatialDat
     plt.close(fig)
 
 
+@pytest.mark.parametrize("dtype", [np.float16, np.float32, np.float64])
+def test_render_labels_rejects_float_dtype(dtype):
+    # Regression test for #606: float-dtype labels must raise a clear "integer dtype" ValueError,
+    # not a cryptic skimage TypeError. spatialdata>=0.8 enforces this at model validation
+    # (parse/construction); on older spatialdata (still supported, >=0.3) our render-time guard is
+    # the safety net. The supported stack must reject them at one of those layers either way.
+    arr = np.zeros((20, 20), dtype=dtype)
+    arr[3:8, 3:8] = 1
+    arr[12:17, 12:17] = 2
+    fig, ax = plt.subplots()
+    try:
+        with pytest.raises(ValueError, match="integer dtype"):
+            sdata = SpatialData(labels={"lbl": Labels2DModel.parse(arr, dims=["y", "x"])})
+            sdata.pl.render_labels("lbl").pl.show(ax=ax)
+    finally:
+        plt.close(fig)
+
+
 def test_render_labels_rejects_background_instance_id_in_table():
     # Regression test for #607: table row with instance_id=0 (background)
     # used to crash with obnscure error.

tests/pl/test_render_labels.py

@@ -564,6 +564,12 @@ def test_plot_can_plot_queried_with_annotation_despite_random_shuffling(self, sd
             filter_table=True,
         )
 
+        # spatialdata's query returns the cropped geometries in a version-dependent order (0.8's
+        # relational-query refactor reorders them), which flips the draw/z-order of the overlapping
+        # circles and so the rendered image. Sort by index for a deterministic draw order, so the
+        # baseline matches across the supported spatialdata range.
+        sdata_cropped["blobs_circles"] = sdata_cropped["blobs_circles"].sort_index()
+
         sdata_cropped.pl.render_shapes("blobs_circles", color="annotation").pl.show()
 
     def test_plot_can_color_two_shapes_elements_by_annotation(self, sdata_blobs: SpatialData):