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Fix SystemError during REPL input compilation corrupting display
When compile() raises SystemError while checking if user input is complete (e.g. due to a compiler bug as in pythongh-150700), two problems occurred: 1. The SystemError propagated out of _more_lines() mid-readline, corrupting the terminal display (traceback appeared before the prompt line was submitted). 2. The SystemError carried _IncompleteInputError as __context__, leaking an internal codeop detail to the user. Fix both by: - Catching SystemError in _more_lines() and returning False (treat input as complete), so readline finishes normally before the error is shown. - Catching SystemError from the second compile in _maybe_compile() and falling through to the final compile, so the resulting exception has no _IncompleteInputError context.
1 parent 1d4e965 commit beb6a48

6 files changed

Lines changed: 23 additions & 7 deletions

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‎Lib/_pyrepl/simple_interact.py‎

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@@ -93,6 +93,8 @@ def _more_lines(console: code.InteractiveConsole, unicodetext: str) -> bool:
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not_empty = last_line.strip() != ""
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incomplete = not last_line.endswith("\n")
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return (was_indented or not_empty) and incomplete
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except SystemError:
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return False
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else:
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return code is None
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‎Lib/code.py‎

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@@ -62,7 +62,7 @@ def runsource(self, source, filename="<input>", symbol="single"):
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"""
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try:
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code = self.compile(source, filename, symbol)
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except (OverflowError, SyntaxError, ValueError):
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except (OverflowError, SyntaxError, ValueError, SystemError):
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# Case 1
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self.showsyntaxerror(filename, source=source)
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return False

‎Lib/codeop.py‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -71,7 +71,7 @@ def _maybe_compile(compiler, source, filename, symbol, flags):
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except SyntaxError:
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pass
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# fallthrough
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``
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return compiler(source, filename, symbol, incomplete_input=False)
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def _compile(source, filename, symbol, incomplete_input=True, *, flags=0):
@@ -147,8 +147,8 @@ def __call__(self, source, filename="<input>", symbol="single"):
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- Return a code object if the command is complete and valid
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- Return None if the command is incomplete
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- Raise SyntaxError, ValueError or OverflowError if the command is a
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syntax error (OverflowError and ValueError can be produced by
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malformed literals).
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- Raise SyntaxError, ValueError, OverflowError or SystemError.
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OverflowError and ValueError can be produced by malformed
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literals, SystemError if source cannot be compiled.
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"""
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return _maybe_compile(self.compiler, source, filename, symbol, flags=self.compiler.flags)

‎Lib/test/test_codeop.py‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6,8 +6,9 @@
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import warnings
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from test.support import warnings_helper
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from textwrap import dedent
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from unittest.mock import Mock
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from codeop import compile_command, PyCF_DONT_IMPLY_DEDENT
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from codeop import compile_command, _maybe_compile, PyCF_DONT_IMPLY_DEDENT
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class CodeopTests(unittest.TestCase):
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@@ -312,6 +313,11 @@ def test_invalid_warning(self):
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self.assertRegex(str(w[0].message), 'invalid escape sequence')
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self.assertEqual(w[0].filename, '<input>')
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def test_systemeror_propagates(self):
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mock_compiler = Mock(side_effect=[SystemError("compiler bug")])
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with self.assertRaises(SystemError):
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_maybe_compile(mock_compiler, "x + 1", "<input>", "single", 0)
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def assertSyntaxErrorMatches(self, code, message):
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with self.subTest(code):
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with self.assertRaisesRegex(SyntaxError, message):
@@ -325,6 +331,5 @@ def foo(x,x):
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"""), "duplicate parameter 'x' in function definition")
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if __name__ == "__main__":
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unittest.main()

‎Lib/test/test_pyrepl/test_interact.py‎

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -275,6 +275,13 @@ def test_incomplete_statement(self):
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console = InteractiveColoredConsole(namespace, filename="<stdin>")
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self.assertTrue(_more_lines(console, code))
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def test_system_error_during_compilation(self):
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namespace = {}
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console = InteractiveColoredConsole(namespace, filename="<stdin>")
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with patch.object(console, "compile", side_effect=SystemError("compiler bug")):
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result = _more_lines(console, "some code")
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self.assertFalse(result)
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class TestWarnings(unittest.TestCase):
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def test_pep_765_warning(self):

‎Misc/NEWS.d/next/Library/2026-06-01-21-31-06.gh-issue-150732.WqHBvP.rst‎

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@@ -0,0 +1,2 @@
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Fix :exc:`SystemError` raised during input compilation in the REPL corrupting
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the display and leaking :exc:`!_IncompleteInputError` in the exception chain.

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