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gh-91167: Fix cloned turtle pen not clearing completely #145406

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gh-91167: Fix cloned turtle pen not clearing completely #145406

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15 changes: 15 additions & 0 deletions Lib/test/test_turtle.py
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Original file line number Diff line number Diff line change
Expand Up @@ -671,6 +671,21 @@ def test_dot_signature(self):
self.assertRaises(turtle.TurtleGraphicsError, self.turtle.dot, 0, (0, 257, 0))
self.assertRaises(turtle.TurtleGraphicsError, self.turtle.dot, 0, 0, 257, 0)

def test_clone_clear_does_not_delete_source_items(self):
screen = self.turtle.screen
screen._delete.reset_mock()
screen._createline.side_effect = lambda: object()

self.turtle.circle(20)
clone = self.turtle.clone()
source_items = set(self.turtle.items)

clone.forward(50)
clone.clear()

deleted_items = {call.args[0] for call in screen._delete.call_args_list}
self.assertFalse(source_items & deleted_items)

Comment on lines +674 to +688
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Copilot AI Mar 2, 2026

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This test only asserts that clone.clear() doesn’t delete items from self.turtle.items, but the bug class here also involves other clone-owned collections (notably stampItems and undobuffer) that can still contain source-owned canvas ids after deepcopy(). Extending the test to cover stamps (e.g., source stamp() then clone.clear()/clearstamps()) and undo behavior (e.g., clone.undo() doesn’t touch source drawings) would prevent regressions once clone() is updated to reinitialize those fields too.

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class TestModuleLevel(unittest.TestCase):
def test_all_signatures(self):
import inspect
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2 changes: 2 additions & 0 deletions Lib/turtle.py
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Expand Up @@ -2879,6 +2879,8 @@ def clone(self):
q.turtle._item = [screen._createpoly() for item in
screen._shapes[self.turtle.shapeIndex]._data]
q.currentLineItem = screen._createline()
q.currentLine = [q._position] if q._drawing else []
q.items = [q.currentLineItem]
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Copilot AI Mar 2, 2026

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clone() still leaves other screen-item ownership state pointing at the source turtle: drawingLineItem is deep-copied (so animated motion can reuse the source’s transient line item), stampItems is deep-copied (so clone.clear()/clearstamps() can delete stamps created by the source), and undobuffer is deep-copied (so clone.undo() can replay/delete the source’s canvas items). Consider reinitializing these fields for q (and resetting any fill-related item ids like _fillitem/_fillpath if filling) so the clone can’t mutate/delete the source turtle’s canvas items via non-clear() operations.

Suggested change
q.items = [q.currentLineItem]
q.items = [q.currentLineItem]
# Reset ownership/undo state so the clone cannot affect the source
# turtle's existing canvas items via non-clear operations.
# The transient animation line item will be recreated on demand.
if hasattr(q, "drawingLineItem"):
q.drawingLineItem = None
# The clone should start with no stamps of its own.
if hasattr(q, "stampItems"):
q.stampItems = []
# Clear the clone's undo history so q.undo() cannot replay or
# delete items created before cloning.
if hasattr(q, "undobuffer"):
reset = getattr(q.undobuffer, "reset", None)
if callable(reset):
reset()
# If a fill operation is active on the source, avoid sharing the
# same fill item/path ids with the clone.
if hasattr(q, "_fillitem") and getattr(self, "_fillitem", None) is not None:
q._fillitem = None
if hasattr(q, "_fillpath") and getattr(self, "_fillitem", None) is not None:
q._fillpath = []

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q._update()
return q

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1 change: 1 addition & 0 deletions Misc/ACKS
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Expand Up @@ -1582,6 +1582,7 @@ Sean Reifschneider
Michael P. Reilly
Bernhard Reiter
Steven Reiz
Yuxing Ren
Roeland Rengelink
Antoine Reversat
Flávio Ribeiro
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