FIX: Remove the deepcopy override from transforms

Let Python take care of the deepcopy for us.

Author: greglucas

lib/matplotlib/tests/test_figure.py

@@ -1,3 +1,4 @@
+import copy
 from datetime import datetime
 import io
 from pathlib import Path
@@ -1261,3 +1262,28 @@ def test_kwargs_pass():
 
     assert fig.get_label() == 'whole Figure'
     assert sub_fig.get_label() == 'sub figure'
+
+
+def test_deepcopy():
+    fig1, ax = plt.subplots()
+    ax.plot([0, 1], [2, 3])
+    ax.set_yscale('log')
+
+    fig2 = copy.deepcopy(fig1)
+
+    # Make sure it is a new object
+    assert fig2.axes[0] is not ax
+    # And that the axis scale got propagated
+    assert fig2.axes[0].get_yscale() == 'log'
+    # Update the deepcopy and check the original isn't modified
+    fig2.axes[0].set_yscale('linear')
+    assert ax.get_yscale() == 'log'
+
+    # And test the limits of the axes don't get propagated
+    ax.set_xlim(1e-1, 1e2)
+    # Draw these to make sure limits are updated
+    fig1.draw_without_rendering()
+    fig2.draw_without_rendering()
+
+    assert ax.get_xlim() == (1e-1, 1e2)
+    assert fig2.axes[0].get_xlim() == (0, 1)

lib/matplotlib/transforms.py

@@ -151,22 +151,6 @@ def __copy__(self):
                 other.set_children(val)  # val == getattr(other, key)
         return other
 
-    def __deepcopy__(self, memo):
-        # We could deepcopy the entire transform tree, but nothing except
-        # `self` is accessible publicly, so we may as well just freeze `self`.
-        other = self.frozen()
-        if other is not self:
-            return other
-        # Some classes implement frozen() as returning self, which is not
-        # acceptable for deepcopying, so we need to handle them separately.
-        other = copy.deepcopy(super(), memo)
-        # If `c = a + b; a1 = copy(a)`, then modifications to `a1` do not
-        # propagate back to `c`, i.e. we need to clear the parents of `a1`.
-        other._parents = {}
-        # If `c = a + b; c1 = copy(c)`, this creates a separate tree
-        # (`c1 = a1 + b1`) so nothing needs to be done.
-        return other
-
     def invalidate(self):
         """
         Invalidate this `TransformNode` and triggers an invalidation of its