Tweak shape repr in _api.check_shape error message.

anntzer · anntzer · commit f37329bef3df · 2023-08-15T22:16:35.000+01:00
Fill in "None" dims *from the end* with the letters N, M, L, K, ... so
as to get e.g. "(N, 2)", "(M, 2, N)", "(L, M, N)", etc.
diff --git a/lib/matplotlib/_api/__init__.py b/lib/matplotlib/_api/__init__.py
@@ -151,12 +151,10 @@ def check_shape(shape, /, **kwargs):
         if (len(data_shape) != len(shape)
                 or any(s != t and t is not None for s, t in zip(data_shape, shape))):
             dim_labels = iter(itertools.chain(
-                'MNLIJKLH',
+                'NMLKJIH',
                 (f"D{i}" for i in itertools.count())))
-            text_shape = ", ".join(str(n)
-                                   if n is not None
-                                   else next(dim_labels)
-                                   for n in shape)
+            text_shape = ", ".join([str(n) if n is not None else next(dim_labels)
+                                    for n in shape[::-1]][::-1])
             if len(shape) == 1:
                 text_shape += ","
 
diff --git a/lib/matplotlib/tests/test_api.py b/lib/matplotlib/tests/test_api.py
@@ -17,17 +17,19 @@
 T = TypeVar('T')
 
 
-@pytest.mark.parametrize('target,test_shape',
-                         [((None, ), (1, 3)),
-                          ((None, 3), (1,)),
-                          ((None, 3), (1, 2)),
-                          ((1, 5), (1, 9)),
-                          ((None, 2, None), (1, 3, 1))
+@pytest.mark.parametrize('target,shape_repr,test_shape',
+                         [((None, ), "(N,)", (1, 3)),
+                          ((None, 3), "(N, 3)", (1,)),
+                          ((None, 3), "(N, 3)", (1, 2)),
+                          ((1, 5), "(1, 5)", (1, 9)),
+                          ((None, 2, None), "(M, 2, N)", (1, 3, 1))
                           ])
 def test_check_shape(target: tuple[int | None, ...],
+                     shape_repr: str,
                      test_shape: tuple[int, ...]) -> None:
-    error_pattern = (f"^'aardvark' must be {len(target)}D.*" +
-                     re.escape(f'has shape {test_shape}'))
+    error_pattern = "^" + re.escape(
+        f"'aardvark' must be {len(target)}D with shape {shape_repr}, but your input "
+        f"has shape {test_shape}")
     data = np.zeros(test_shape)
     with pytest.raises(ValueError, match=error_pattern):
         _api.check_shape(target, aardvark=data)
