Copy new attributes in Collection.update_from.

These were added in #18480, and not copying them can mean that an artist
that used `update_from` could get in an inconsistent state.

For example, this will fix legends of colour-mapped scatter plots, where
a copy of the scatter Collection is made to go in the legend.

Fixes #19779.

lib/matplotlib/collections.py

@@ -944,8 +944,11 @@ def update_from(self, other):
 
         artist.Artist.update_from(self, other)
         self._antialiaseds = other._antialiaseds
+        self._mapped_colors = other._mapped_colors
+        self._edge_is_mapped = other._edge_is_mapped
         self._original_edgecolor = other._original_edgecolor
         self._edgecolors = other._edgecolors
+        self._face_is_mapped = other._face_is_mapped
         self._original_facecolor = other._original_facecolor
         self._facecolors = other._facecolors
         self._linewidths = other._linewidths
@@ -958,7 +961,7 @@ def update_from(self, other):
         self._A = other._A
         self.norm = other.norm
         self.cmap = other.cmap
-        # do we need to copy self._update_dict? -JJL
+        self._update_dict = other._update_dict.copy()
         self.stale = True
 
 

lib/matplotlib/tests/test_axes.py

@@ -52,14 +52,16 @@ def test_get_labels():
 @check_figures_equal()
 def test_label_loc_vertical(fig_test, fig_ref):
     ax = fig_test.subplots()
-    sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+    sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+    ax.legend()
     ax.set_ylabel('Y Label', loc='top')
     ax.set_xlabel('X Label', loc='right')
     cbar = fig_test.colorbar(sc)
     cbar.set_label("Z Label", loc='top')
 
     ax = fig_ref.subplots()
-    sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+    sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+    ax.legend()
     ax.set_ylabel('Y Label', y=1, ha='right')
     ax.set_xlabel('X Label', x=1, ha='right')
     cbar = fig_ref.colorbar(sc)
@@ -69,14 +71,16 @@ def test_label_loc_vertical(fig_test, fig_ref):
 @check_figures_equal()
 def test_label_loc_horizontal(fig_test, fig_ref):
     ax = fig_test.subplots()
-    sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+    sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+    ax.legend()
     ax.set_ylabel('Y Label', loc='bottom')
     ax.set_xlabel('X Label', loc='left')
     cbar = fig_test.colorbar(sc, orientation='horizontal')
     cbar.set_label("Z Label", loc='left')
 
     ax = fig_ref.subplots()
-    sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+    sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+    ax.legend()
     ax.set_ylabel('Y Label', y=0, ha='left')
     ax.set_xlabel('X Label', x=0, ha='left')
     cbar = fig_ref.colorbar(sc, orientation='horizontal')
@@ -88,14 +92,16 @@ def test_label_loc_rc(fig_test, fig_ref):
     with matplotlib.rc_context({"xaxis.labellocation": "right",
                                 "yaxis.labellocation": "top"}):
         ax = fig_test.subplots()
-        sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+        sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+        ax.legend()
         ax.set_ylabel('Y Label')
         ax.set_xlabel('X Label')
         cbar = fig_test.colorbar(sc, orientation='horizontal')
         cbar.set_label("Z Label")
 
     ax = fig_ref.subplots()
-    sc = ax.scatter([1, 2], [1, 2], c=[1, 2])
+    sc = ax.scatter([1, 2], [1, 2], c=[1, 2], label='scatter')
+    ax.legend()
     ax.set_ylabel('Y Label', y=1, ha='right')
     ax.set_xlabel('X Label', x=1, ha='right')
     cbar = fig_ref.colorbar(sc, orientation='horizontal')