deprecate fig.add_axes() with no arguments

KSafran · KSafran · commit 31e7ceb1d3cf · 2019-09-18T11:21:15.000-04:00
diff --git a/doc/api/next_api_changes/deprecated_empty_add_axes.rst b/doc/api/next_api_changes/deprecated_empty_add_axes.rst
@@ -0,0 +1,5 @@
+Deprecations
+````````````
+
+Calling ``fig.add_axes()`` with no arguments currently return None,
+will raise an error in the future
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -1221,6 +1221,11 @@ def add_axes(self, *args, **kwargs):
         """
 
         if not len(args):
+            cbook.warn_deprecated(
+                "3.3",
+                message="Calling add_axes() without argument is "
+                "deprecated. You may want to use add_suplot() "
+                "instead.")
             return
 
         # shortcut the projection "key" modifications later on, if an axes
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -141,6 +141,10 @@ def test_figure_legend():
 def test_gca():
     fig = plt.figure()
 
+    with pytest.warns(UserWarning):
+        # empty call to add_axes() will throw deprecation warning
+        assert fig.add_axes() is None
+
     ax1 = fig.add_axes([0, 0, 1, 1])
     assert fig.gca(projection='rectilinear') is ax1
     assert fig.gca() is ax1
