8000 bpo-32912: Revert SyntaxWarning on invalid escape sequences. (GH-15195) · python/cpython@b4be87a · GitHub
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bpo-32912: Revert SyntaxWarning on invalid escape sequences. (GH-15195)
DeprecationWarning will continue to be emitted for invalid escape sequences in string and bytes literals just as it did in 3.7. SyntaxWarning may be emitted in the future. But per mailing list discussion, we don't yet know when because we haven't settled on how to do so in a non-disruptive manner. (Applies 4c5b6ba to the master branch). (This is #15142 for master/3.9) https://bugs.python.org/issue32912 Automerge-Triggered-By: @gpshead
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‎Doc/reference/lexical_analysis.rst

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@@ -594,11 +594,9 @@ escape sequences only recognized in string literals fall into the category of
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unrecognized escapes for bytes literals.
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.. versionchanged:: 3.6
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Unrecognized escape sequences produce a :exc:`DeprecationWarning`.
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.. versionchanged:: 3.8
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Unrecognized escape sequences produce a :exc:`SyntaxWarning`. In
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some future version of Python they will be a :exc:`SyntaxError`.
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Unrecognized escape sequences produce a :exc:`DeprecationWarning`. In
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a future Python version they will be a :exc:`SyntaxWarning` and
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eventually a :exc:`SyntaxError`.
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Even in a raw literal, quotes can be escaped with a backslash, but the
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backslash remains in the result; for example, ``r"\""`` is a valid string

‎Doc/whatsnew/3.8.rst

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@@ -414,11 +414,6 @@ Other Language Changes
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and :keyword:`return` statements.
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(Contributed by David Cuthbert and Jordan Chapman in :issue:`32117`.)
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* A backslash-character pair that is not a valid escape sequence generates
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a :exc:`DeprecationWarning` since Python 3.6. In Python 3.8 it generates
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a :exc:`SyntaxWarning` instead.
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(Contributed by Serhiy Storchaka in :issue:`32912`.)
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* The compiler now produces a :exc:`SyntaxWarning` in some cases when a comma
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is missed before tuple or list. For example::
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‎Lib/test/test_fstring.py

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Original file line numberDiff line numberDiff line change
@@ -649,7 +649,7 @@ def test_backslashes_in_string_part(self):
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self.assertEqual(f'2\x203', '2 3')
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self.assertEqual(f'\x203', ' 3')
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with self.assertWarns(SyntaxWarning): # invalid escape sequence
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with self.assertWarns(DeprecationWarning): # invalid escape sequence
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value = eval(r"f'\{6*7}'")
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self.assertEqual(value, '\\42')
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self.assertEqual(f'\\{6*7}', '\\42')

‎Lib/test/test_string_literals.py

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@@ -32,6 +32,7 @@
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import shutil
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import tempfile
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import unittest
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import warnings
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TEMPLATE = r"""# coding: %s
@@ -110,10 +111,24 @@ def test_eval_str_invalid_escape(self):
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for b in range(1, 128):
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if b in b"""\n\r"'01234567NU\\abfnrtuvx""":
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continue
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with self.assertWarns(SyntaxWarning):
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with self.assertWarns(DeprecationWarning):
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self.assertEqual(eval(r"'\%c'" % b), '\\' + chr(b))
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self.check_syntax_warning("'''\n\\z'''")
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with warnings.catch_warnings(record=True) as w:
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warnings.simplefilter('always', category=DeprecationWarning)
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eval("'''\n\\z'''")
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self.assertEqual(len(w), 1)
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self.assertEqual(w[0].filename, '<string>')
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self.assertEqual(w[0].lineno, 1)
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with warnings.catch_warnings(record=True) as w:
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warnings.simplefilter('error', category=DeprecationWarning)
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with self.assertRaises(SyntaxError) as cm:
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eval("'''\n\\z'''")
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exc = cm.exception
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self.assertEqual(w, [])
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self.assertEqual(exc.filename, '<string>')
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self.assertEqual(exc.lineno, 1)
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def test_eval_str_raw(self):
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self.assertEqual(eval(""" r'x' """), 'x')
@@ -145,10 +160,24 @@ def test_eval_bytes_invalid_escape(self):
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for b in range(1, 128):
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if b in b"""\n\r"'01234567\\abfnrtvx""":
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continue
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with self.assertWarns(SyntaxWarning):
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with self.assertWarns(DeprecationWarning):
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self.assertEqual(eval(r"b'\%c'" % b), b'\\' + bytes([b]))
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self.check_syntax_warning("b'''\n\\z'''")
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with warnings.catch_warnings(record=True) as w:
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warnings.simplefilter('always', category=DeprecationWarning)
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eval("b'''\n\\z'''")
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self.assertEqual(len(w), 1)
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self.assertEqual(w[0].filename, '<string>')
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self.assertEqual(w[0].lineno, 1)
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with warnings.catch_warnings(record=True) as w:
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warnings.simplefilter('error', category=DeprecationWarning)
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with self.assertRaises(SyntaxError) as cm:
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eval("b'''\n\\z'''")
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exc = cm.exception
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self.assertEqual(w, [])
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self.assertEqual(exc.filename, '<string>')
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self.assertEqual(exc.lineno, 1)
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def test_eval_bytes_raw(self):
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self.assertEqual(eval(""" br'x' """), b'x')
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‎Misc/NEWS.d/next/Core and Builtins/2019-08-06-14-03-59.bpo-32912.UDwSMJ.rst

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@@ -0,0 +1,3 @@
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Reverted :issue:`32912`: emitting :exc:`SyntaxWarning` instead of
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:exc:`DeprecationWarning` for invalid escape sequences in string and bytes
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literals.

‎Python/ast.c

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Original file line numberDiff line numberDiff line change
@@ -4671,12 +4671,12 @@ warn_invalid_escape_sequence(struct compiling *c, const node *n,
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if (msg == NULL) {
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return -1;
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}
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if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning, msg,
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if (PyErr_WarnExplicitObject(PyExc_DeprecationWarning, msg,
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c->c_filename, LINENO(n),
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NULL, NULL) < 0)
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{
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if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
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/* Replace the SyntaxWarning exception with a SyntaxError
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if (PyErr_ExceptionMatches(PyExc_DeprecationWarning)) {
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/* Replace the DeprecationWarning exception with a SyntaxError
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to get a more accurate error report */
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PyErr_Clear();
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ast_error(c, n, "%U", msg);

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