Simplify shape-checking in QuadMesh.set_array.

This can be done now that the previously existing allowance for `A`
having the wrong shape but right number of elements has been removed.

Also, raising ValueError in all cases is more consistent.

Author: anntzer

doc/api/next_api_changes/behavior/24829-AL.rst

@@ -0,0 +1,3 @@
+``QuadMesh.set_array`` now always raises ``ValueError`` for inputs with incorrect shapes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It could previously also raise `TypeError` in some cases.

lib/matplotlib/collections.py

@@ -1960,9 +1960,9 @@ def set_array(self, A):
         A : array-like
             The mesh data. Supported array shapes are:
 
-            - (M, N) or M*N: a mesh with scalar data. The values are mapped to
-              colors using normalization and a colormap. See parameters *norm*,
-              *cmap*, *vmin*, *vmax*.
+            - (M, N) or (M*N,): a mesh with scalar data. The values are mapped
+              to colors using normalization and a colormap. See parameters
+              *norm*, *cmap*, *vmin*, *vmax*.
             - (M, N, 3): an image with RGB values (0-1 float or 0-255 int).
             - (M, N, 4): an image with RGBA values (0-1 float or 0-255 int),
               i.e. including transparency.
@@ -1974,44 +1974,18 @@ def set_array(self, A):
             shading.
         """
         height, width = self._coordinates.shape[0:-1]
-        misshapen_data = False
-        faulty_data = False
-
         if self._shading == 'flat':
-            h, w = height-1, width-1
+            h, w = height - 1, width - 1
         else:
             h, w = height, width
-
+        ok_shapes = [(h, w, 3), (h, w, 4), (h, w), (h * w,)]
         if A is not None:
             shape = np.shape(A)
-            if len(shape) == 1:
-                if shape[0] != (h*w):
-                    faulty_data = True
-            elif shape[:2] != (h, w):
-                if np.prod(shape[:2]) == (h * w):
-                    misshapen_data = True
-                else:
-                    faulty_data = True
-            elif len(shape) == 3 and shape[2] not in {3, 4}:
-                # 3D data must be RGB(A) (h, w, [3,4])
-                # the (h, w) check is taken care of above
-                raise ValueError(
-                    f"For X ({width}) and Y ({height}) with "
-                    f"{self._shading} shading, the expected shape of "
-                    f"A with RGB(A) colors is ({h}, {w}, [3 or 4]), not "
-                    f"{A.shape}")
-
-            if misshapen_data:
+            if shape not in ok_shapes:
                 raise ValueError(
                     f"For X ({width}) and Y ({height}) with {self._shading} "
-                    f"shading, the expected shape of A is ({h}, {w}), not "
-                    f"{A.shape}")
-
-            if faulty_data:
-                raise TypeError(
-                    f"Dimensions of A {A.shape} are incompatible with "
-                    f"X ({width}) and/or Y ({height})")
-
+                    f"shading, A should have shape "
+                    f"{' or '.join(map(str, ok_shapes))}, not {A.shape}")
         return super().set_array(A)
 
     def get_datalim(self, transData):

lib/matplotlib/tests/test_collections.py

@@ -1,6 +1,7 @@
+from datetime import datetime
 import io
+import re
 from types import SimpleNamespace
-from datetime import datetime
 
 import numpy as np
 from numpy.testing import assert_array_equal, assert_array_almost_equal
@@ -817,36 +818,38 @@ def test_quadmesh_set_array_validation():
     fig, ax = plt.subplots()
     coll = ax.pcolormesh(x, y, z)
 
-    # Test deprecated warning when faulty shape is passed.
-    with pytest.raises(ValueError, match=r"For X \(11\) and Y \(8\) with flat "
-                       r"shading, the expected shape of A is \(7, 10\), not "
-                       r"\(10, 7\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (10, 7)")):
         coll.set_array(z.reshape(10, 7))
 
     z = np.arange(54).reshape((6, 9))
-    with pytest.raises(TypeError, match=r"Dimensions of A \(6, 9\) "
-                       r"are incompatible with X \(11\) and/or Y \(8\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (6, 9)")):
         coll.set_array(z)
-    with pytest.raises(TypeError, match=r"Dimensions of A \(54,\) "
-                       r"are incompatible with X \(11\) and/or Y \(8\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (54,)")):
         coll.set_array(z.ravel())
 
     # RGB(A) tests
     z = np.ones((9, 6, 3))  # RGB with wrong X/Y dims
-    with pytest.raises(TypeError, match=r"Dimensions of A \(9, 6, 3\) "
-                       r"are incompatible with X \(11\) and/or Y \(8\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (9, 6, 3)")):
         coll.set_array(z)
 
     z = np.ones((9, 6, 4))  # RGBA with wrong X/Y dims
-    with pytest.raises(TypeError, match=r"Dimensions of A \(9, 6, 4\) "
-                       r"are incompatible with X \(11\) and/or Y \(8\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (9, 6, 4)")):
         coll.set_array(z)
 
     z = np.ones((7, 10, 2))  # Right X/Y dims, bad 3rd dim
-    with pytest.raises(ValueError, match=r"For X \(11\) and Y \(8\) with "
-                       r"flat shading, the expected shape of "
-                       r"A with RGB\(A\) colors is \(7, 10, \[3 or 4\]\), "
-                       r"not \(7, 10, 2\)"):
+    with pytest.raises(ValueError, match=re.escape(
+            "For X (11) and Y (8) with flat shading, A should have shape "
+            "(7, 10, 3) or (7, 10, 4) or (7, 10) or (70,), not (7, 10, 2)")):
         coll.set_array(z)
 
     x = np.arange(10)