FIX: restore creating new axes via plt.subplot with different kwargs

tacaswell · tacaswell · commit 29604906e7a9 · 2021-02-02T18:00:03.000-05:00
This adds a small amount of additional state to the Axes created via Figure.add_axes and Figure.add_subplot (which the other Axes creation methods eventually funnel through) to track the kwargs passed through. We then use that state in `pyplot.subplot` to determine if we should re-use an Axes found at a given position or create a new one (and implicitly destroy the existing one). closes #19432
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -576,12 +576,12 @@ def add_axes(self, *args, **kwargs):
             if not np.isfinite(rect).all():
                 raise ValueError('all entries in rect must be finite '
                                  'not {}'.format(rect))
-            projection_class, kwargs = self._process_projection_requirements(
+            projection_class, pkw = self._process_projection_requirements(
                 *args, **kwargs)
 
             # create the new axes using the axes class given
-            a = projection_class(self, rect, **kwargs)
-        return self._add_axes_internal(a)
+            a = projection_class(self, rect, **pkw)
+        return self._add_axes_internal(a, kwargs)
 
     @docstring.dedent_interpd
     def add_subplot(self, *args, **kwargs):
@@ -706,17 +706,18 @@ def add_subplot(self, *args, **kwargs):
             if (len(args) == 1 and isinstance(args[0], Integral)
                     and 100 <= args[0] <= 999):
                 args = tuple(map(int, str(args[0])))
-            projection_class, kwargs = self._process_projection_requirements(
+            projection_class, pkw = self._process_projection_requirements(
                 *args, **kwargs)
-            ax = subplot_class_factory(projection_class)(self, *args, **kwargs)
-        return self._add_axes_internal(ax)
+            ax = subplot_class_factory(projection_class)(self, *args, **pkw)
+        return self._add_axes_internal(ax, kwargs)
 
-    def _add_axes_internal(self, ax):
+    def _add_axes_internal(self, ax, input_kwargs):
         """Private helper for `add_axes` and `add_subplot`."""
         self._axstack.push(ax)
         self._localaxes.push(ax)
         self.sca(ax)
         ax._remove_method = self.delaxes
+        ax._init_kwargs = input_kwargs
         self.stale = True
         ax.stale_callback = _stale_figure_callback
         return ax
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -1229,8 +1229,8 @@ def subplot(*args, **kwargs):
          if hasattr(ax, 'get_subplotspec') and ax.get_subplotspec() == key),
         None)
 
-    # If no existing axes match, then create a new one.
-    if ax is None:
+    # If no existing axes matches, then create a new one.
+    if ax is None or getattr(ax, '_init_kwargs', {}) != kwargs:
         ax = fig.add_subplot(*args, **kwargs)
 
     bbox = ax.bbox
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
@@ -1010,18 +1010,27 @@ def test_axes_kwargs():
     plt.close()
 
     # plt.subplot() searches for axes with the same subplot spec, and if one
-    # exists, returns it, regardless of whether the axes kwargs were the same.
+    # exists, and the kwargs match returns it, create a new one if they do not
     fig = plt.figure()
     ax = plt.subplot(1, 2, 1)
     ax1 = plt.subplot(1, 2, 1)
     ax2 = plt.subplot(1, 2, 2)
+    # This will delete ax / ax1 as they fully overlap
     ax3 = plt.subplot(1, 2, 1, projection='polar')
+    ax4 = plt.subplot(1, 2, 1, projection='polar')
     assert ax is not None
     assert ax1 is ax
     assert ax2 is not ax
-    assert ax3 is ax
+    assert ax3 is not ax
+    assert ax3 is ax4
+
+    assert ax not in fig.axes
+    assert ax2 in fig.axes
+    assert ax3 in fig.axes
+
     assert ax.name == 'rectilinear'
-    assert ax3.name == 'rectilinear'
+    assert ax2.name == 'rectilinear'
+    assert ax3.name == 'polar'
     plt.close()
 
     # plt.gca() returns an existing axes, unless there were no axes.
