Merge pull request matplotlib#18839 from tacaswell/fix_Text_update_mutating_input

MNT: make sure we do not mutate input in Text.update

Author: timhoffm

lib/matplotlib/tests/test_text.py

@@ -8,10 +8,12 @@
 
 import matplotlib as mpl
 from matplotlib.backend_bases import MouseEvent
+from matplotlib.font_manager import FontProperties
 import matplotlib.patches as mpatches
 import matplotlib.pyplot as plt
 import matplotlib.transforms as mtransforms
 from matplotlib.testing.decorators import check_figures_equal, image_comparison
+from matplotlib.text import Text
 
 
 needs_usetex = pytest.mark.skipif(
@@ -697,3 +699,13 @@ def test_transform_rotates_text():
                    transform_rotates_text=True)
     result = text.get_rotation()
     assert_almost_equal(result, 30)
+
+
+def test_update_mutate_input():
+    inp = dict(fontproperties=FontProperties(weight="bold"),
+               bbox=None)
+    cache = dict(inp)
+    t = Text()
+    t.update(inp)
+    assert inp['fontproperties'] == cache['fontproperties']
+    assert inp['bbox'] == cache['bbox']

lib/matplotlib/text.py

@@ -172,6 +172,8 @@ def __init__(self,
 
     def update(self, kwargs):
         # docstring inherited
+        # make a copy so we do not mutate user input!
+        kwargs = dict(kwargs)
         sentinel = object()  # bbox can be None, so use another sentinel.
         # Update fontproperties first, as it has lowest priority.
         fontproperties = kwargs.pop("fontproperties", sentinel)