Properly deprecate non-1D inputs to pie().

anntzer · anntzer · commit 7b80f6ca5328 · 2019-02-06T22:41:49.000+01:00
This PR also restores (... for the duration of the deprecation) the
support for non-1D inputs that can be squeezed to a 1D array that was
broken with numpy 1.16.
diff --git a/doc/api/next_api_changes/2018-02-03-AL.rst b/doc/api/next_api_changes/2018-02-03-AL.rst
@@ -0,0 +1,5 @@
+Deprecations
+````````````
+
+Passing a non-1D (typically, (n, 1)-shaped) input to `Axes.pie` is deprecated.
+Pass a 1D array instead.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -2809,11 +2809,19 @@ def pie(self, x, explode=None, labels=None, colors=None,
         The axes aspect ratio can be controlled with `Axes.set_aspect`.
         """
         self.set_aspect('equal')
-        x = np.array(x, np.float32)
+        # The use of float32 is "historical", but can't be changed without
+        # regenerating the test baselines.
+        x = np.asarray(x, np.float32)
+        if x.ndim != 1 and x.squeeze().ndim <= 1:
+            cbook.warn_deprecated(
+                "3.1", message="Non-1D inputs to pie() are currently "
+                "squeeze()d, but this behavior is deprecated since %(since)s "
+                "and will be removed %(removal)s; pass a 1D array instead.")
+            x = np.atleast_1d(x.squeeze())
 
         sx = x.sum()
         if sx > 1:
-            x /= sx
+            x = x / sx
 
         if labels is None:
             labels = [''] * len(x)
