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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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gpshead authored and miss-islington committed Aug 10, 2019
1 parent 92c7e30 commit b4be87a04a2a8ccfd2480e19dc527589fce53555
@@ -594,11 +594,9 @@ escape sequences only recognized in string literals fall into the category of
unrecognized escapes for bytes literals.

.. versionchanged:: 3.6
Unrecognized escape sequences produce a :exc:`DeprecationWarning`.

.. versionchanged:: 3.8
Unrecognized escape sequences produce a :exc:`SyntaxWarning`. In
some future version of Python they will be a :exc:`SyntaxError`.
Unrecognized escape sequences produce a :exc:`DeprecationWarning`. In
a future Python version they will be a :exc:`SyntaxWarning` and
eventually a :exc:`SyntaxError`.

Even in a raw literal, quotes can be escaped with a backslash, but the
backslash remains in the result; for example, ``r"\""`` is a valid string
@@ -414,11 +414,6 @@ Other Language Changes
and :keyword:`return` statements.
(Contributed by David Cuthbert and Jordan Chapman in :issue:`32117`.)

* A backslash-character pair that is not a valid escape sequence generates
a :exc:`DeprecationWarning` since Python 3.6. In Python 3.8 it generates
a :exc:`SyntaxWarning` instead.
(Contributed by Serhiy Storchaka in :issue:`32912`.)

* The compiler now produces a :exc:`SyntaxWarning` in some cases when a comma
is missed before tuple or list. For example::

@@ -649,7 +649,7 @@ def test_backslashes_in_string_part(self):
self.assertEqual(f'2\x203', '2 3')
self.assertEqual(f'\x203', ' 3')

with self.assertWarns(SyntaxWarning): # invalid escape sequence
with self.assertWarns(DeprecationWarning): # invalid escape sequence
value = eval(r"f'\{6*7}'")
self.assertEqual(value, '\\42')
self.assertEqual(f'\\{6*7}', '\\42')
@@ -32,6 +32,7 @@
import shutil
import tempfile
import unittest
import warnings


TEMPLATE = r"""# coding: %s
@@ -110,10 +111,24 @@ def test_eval_str_invalid_escape(self):
for b in range(1, 128):
if b in b"""\n\r"'01234567NU\\abfnrtuvx""":
continue
with self.assertWarns(SyntaxWarning):
with self.assertWarns(DeprecationWarning):
self.assertEqual(eval(r"'\%c'" % b), '\\' + chr(b))

self.check_syntax_warning("'''\n\\z'''")
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('always', category=DeprecationWarning)
eval("'''\n\\z'''")
self.assertEqual(len(w), 1)
self.assertEqual(w[0].filename, '<string>')
self.assertEqual(w[0].lineno, 1)

with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('error', category=DeprecationWarning)
with self.assertRaises(SyntaxError) as cm:
eval("'''\n\\z'''")
exc = cm.exception
self.assertEqual(w, [])
self.assertEqual(exc.filename, '<string>')
self.assertEqual(exc.lineno, 1)

def test_eval_str_raw(self):
self.assertEqual(eval(""" r'x' """), 'x')
@@ -145,10 +160,24 @@ def test_eval_bytes_invalid_escape(self):
for b in range(1, 128):
if b in b"""\n\r"'01234567\\abfnrtvx""":
continue
with self.assertWarns(SyntaxWarning):
with self.assertWarns(DeprecationWarning):
self.assertEqual(eval(r"b'\%c'" % b), b'\\' + bytes([b]))

self.check_syntax_warning("b'''\n\\z'''")
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('always', category=DeprecationWarning)
eval("b'''\n\\z'''")
self.assertEqual(len(w), 1)
self.assertEqual(w[0].filename, '<string>')
self.assertEqual(w[0].lineno, 1)

with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('error', category=DeprecationWarning)
with self.assertRaises(SyntaxError) as cm:
eval("b'''\n\\z'''")
exc = cm.exception
self.assertEqual(w, [])
self.assertEqual(exc.filename, '<string>')
self.assertEqual(exc.lineno, 1)

def test_eval_bytes_raw(self):
self.assertEqual(eval(""" br'x' """), b'x')
@@ -0,0 +1,3 @@
Reverted :issue:`32912`: emitting :exc:`SyntaxWarning` instead of
:exc:`DeprecationWarning` for invalid escape sequences in string and bytes
literals.
@@ -4671,12 +4671,12 @@ warn_invalid_escape_sequence(struct compiling *c, const node *n,
if (msg == NULL) {
return -1;
}
if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning, msg,
if (PyErr_WarnExplicitObject(PyExc_DeprecationWarning, msg,
c->c_filename, LINENO(n),
NULL, NULL) < 0)
{
if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
/* Replace the SyntaxWarning exception with a SyntaxError
if (PyErr_ExceptionMatches(PyExc_DeprecationWarning)) {
/* Replace the DeprecationWarning exception with a SyntaxError
to get a more accurate error report */
PyErr_Clear();
ast_error(c, n, "%U", msg);

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