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Issue 27948: Allow backslashes in the literal string portion of f-strings, but not in the expressions. Also, require expressions to begin and end with literal curly braces.

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This commit is contained in:
Eric V. Smith 2016-09-09 21:56:20 -04:00
parent 052828db15
commit 451d0e38fc
9 changed files with 321 additions and 341 deletions
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120
Lib/test/test_fstring.py
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@ -119,6 +119,14 @@ f'{a * x()}'"""
self.assertEqual(f'a}}', 'a}')
self.assertEqual(f'}}b', '}b')
self.assertEqual(f'a}}b', 'a}b')
self.assertEqual(f'{{}}', '{}')
self.assertEqual(f'a{{}}', 'a{}')
self.assertEqual(f'{{b}}', '{b}')
self.assertEqual(f'{{}}c', '{}c')
self.assertEqual(f'a{{b}}', 'a{b}')
self.assertEqual(f'a{{}}c', 'a{}c')
self.assertEqual(f'{{b}}c', '{b}c')
self.assertEqual(f'a{{b}}c', 'a{b}c')
self.assertEqual(f'{{{10}', '{10')
self.assertEqual(f'}}{10}', '}10')
@ -302,56 +310,79 @@ f'{a * x()}'"""
["f'{\n}'",
])
def test_no_backslashes(self):
# See issue 27921
def test_backslashes_in_string_part(self):
self.assertEqual(f'\t', '\t')
self.assertEqual(r'\t', '\\t')
self.assertEqual(rf'\t', '\\t')
self.assertEqual(f'{2}\t', '2\t')
self.assertEqual(f'{2}\t{3}', '2\t3')
self.assertEqual(f'\t{3}', '\t3')
# These should work, but currently don't
self.assertAllRaise(SyntaxError, 'backslashes not allowed',
[r"f'\t'",
r"f'{2}\t'",
r"f'{2}\t{3}'",
r"f'\t{3}'",
self.assertEqual(f'\u0394', '\u0394')
self.assertEqual(r'\u0394', '\\u0394')
self.assertEqual(rf'\u0394', '\\u0394')
self.assertEqual(f'{2}\u0394', '2\u0394')
self.assertEqual(f'{2}\u0394{3}', '2\u03943')
self.assertEqual(f'\u0394{3}', '\u03943')
r"f'\N{GREEK CAPITAL LETTER DELTA}'",
r"f'{2}\N{GREEK CAPITAL LETTER DELTA}'",
r"f'{2}\N{GREEK CAPITAL LETTER DELTA}{3}'",
r"f'\N{GREEK CAPITAL LETTER DELTA}{3}'",
self.assertEqual(f'\U00000394', '\u0394')
self.assertEqual(r'\U00000394', '\\U00000394')
self.assertEqual(rf'\U00000394', '\\U00000394')
self.assertEqual(f'{2}\U00000394', '2\u0394')
self.assertEqual(f'{2}\U00000394{3}', '2\u03943')
self.assertEqual(f'\U00000394{3}', '\u03943')
r"f'\u0394'",
r"f'{2}\u0394'",
r"f'{2}\u0394{3}'",
r"f'\u0394{3}'",
self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}', '\u0394')
self.assertEqual(f'{2}\N{GREEK CAPITAL LETTER DELTA}', '2\u0394')
self.assertEqual(f'{2}\N{GREEK CAPITAL LETTER DELTA}{3}', '2\u03943')
self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}{3}', '\u03943')
self.assertEqual(f'2\N{GREEK CAPITAL LETTER DELTA}', '2\u0394')
self.assertEqual(f'2\N{GREEK CAPITAL LETTER DELTA}3', '2\u03943')
self.assertEqual(f'\N{GREEK CAPITAL LETTER DELTA}3', '\u03943')
r"f'\U00000394'",
r"f'{2}\U00000394'",
r"f'{2}\U00000394{3}'",
r"f'\U00000394{3}'",
self.assertEqual(f'\x20', ' ')
self.assertEqual(r'\x20', '\\x20')
self.assertEqual(rf'\x20', '\\x20')
self.assertEqual(f'{2}\x20', '2 ')
self.assertEqual(f'{2}\x20{3}', '2 3')
self.assertEqual(f'\x20{3}', ' 3')
r"f'\x20'",
r"f'{2}\x20'",
r"f'{2}\x20{3}'",
r"f'\x20{3}'",
self.assertEqual(f'2\x20', '2 ')
self.assertEqual(f'2\x203', '2 3')
self.assertEqual(f'\x203', ' 3')
r"f'2\x20'",
r"f'2\x203'",
r"f'2\x203'",
def test_misformed_unicode_character_name(self):
# These test are needed because unicode names are parsed
# differently inside f-strings.
self.assertAllRaise(SyntaxError, r"\(unicode error\) 'unicodeescape' codec can't decode bytes in position .*: malformed \\N character escape",
[r"f'\N'",
r"f'\N{'",
r"f'\N{GREEK CAPITAL LETTER DELTA'",
# Here are the non-f-string versions,
# which should give the same errors.
r"'\N'",
r"'\N{'",
r"'\N{GREEK CAPITAL LETTER DELTA'",
])
# And these don't work now, and shouldn't work in the future.
self.assertAllRaise(SyntaxError, 'backslashes not allowed',
def test_no_backslashes_in_expression_part(self):
self.assertAllRaise(SyntaxError, 'f-string expression part cannot include a backslash',
[r"f'{\'a\'}'",
r"f'{\t3}'",
r"f'{\}'",
r"rf'{\'a\'}'",
r"rf'{\t3}'",
r"rf'{\}'",
r"""rf'{"\N{LEFT CURLY BRACKET}"}'""",
])
# add this when backslashes are allowed again. see issue 27921
# these test will be needed because unicode names will be parsed
# differently once backslashes are allowed inside expressions
## def test_misformed_unicode_character_name(self):
## self.assertAllRaise(SyntaxError, 'xx',
## [r"f'\N'",
## [r"f'\N{'",
## [r"f'\N{GREEK CAPITAL LETTER DELTA'",
## ])
def test_no_escapes_for_braces(self):
# \x7b is '{'. Make sure it doesn't start an expression.
self.assertEqual(f'\x7b2}}', '{2}')
self.assertEqual(f'\x7b2', '{2')
self.assertEqual(f'\u007b2', '{2')
self.assertEqual(f'\N{LEFT CURLY BRACKET}2\N{RIGHT CURLY BRACKET}', '{2}')
def test_newlines_in_expressions(self):
self.assertEqual(f'{0}', '0')
@ -509,6 +540,14 @@ f'{a * x()}'"""
"ruf''",
"FUR''",
"Fur''",
"fb''",
"fB''",
"Fb''",
"FB''",
"bf''",
"bF''",
"Bf''",
"BF''",
])
def test_leading_trailing_spaces(self):
@ -551,8 +590,8 @@ f'{a * x()}'"""
self.assertAllRaise(SyntaxError, 'f-string: invalid conversion character',
["f'{3!g}'",
"f'{3!A}'",
"f'{3!A}'",
"f'{3!A}'",
"f'{3!3}'",
"f'{3!G}'",
"f'{3!!}'",
"f'{3!:}'",
"f'{3! s}'", # no space before conversion char
@ -601,6 +640,7 @@ f'{a * x()}'"""
"f'{3!s:3'",
"f'x{'",
"f'x{x'",
"f'{x'",
"f'{3:s'",
"f'{{{'",
"f'{{}}{'",