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Merged
pablogsal merged 5 commits into from
Apr 13, 2023
Merged

capture more errors in fstring replacement field #67

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040810a
capture more errors in fstring replacement field
sunmy2019 Apr 9, 2023
2470dfa
add some specific rules
sunmy2019 Apr 10, 2023
11cd51b
add an entity for empty expression, fix tests
sunmy2019 Apr 12, 2023
143524b
specialize error message for `lambda`
sunmy2019 Apr 12, 2023
91faa31
handle `lambda` in f-string
sunmy2019 Apr 12, 2023
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31 changes: 21 additions & 10 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -1140,6 +1140,8 @@ invalid_expression:
_PyPegen_check_legacy_stmt(p, a) ? NULL : p->tokens[p->mark-1]->level == 0 ? NULL :
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax. Perhaps you forgot a comma?") }
| a=disjunction 'if' b=disjunction !('else'|':') { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "expected 'else' after 'if' expression") }
| a='lambda' [lambda_params] b=':' &(FSTRING_MIDDLE | fstring_replacement_field) {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "f-string: lambda expressions are not allowed without parentheses") }

invalid_named_expression(memo):
| a=expression ':=' expression {
Expand Down Expand Up @@ -1358,14 +1360,23 @@ invalid_kvpair:
invalid_starred_expression:
| a='*' expression '=' b=expression { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "cannot assign to iterable argument unpacking") }
invalid_replacement_field:
| '{' a='=' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: expression required before '='") }
| '{' a=':' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: expression required before ':'") }
| '{' a='!' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: expression required before '!'") }
| '{' a='}' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: empty expression not allowed") }
| '{' (yield_expr | star_expressions) "="? invalid_conversion_character
# We explicitly require either a conversion character or a format spec (or both) in order for this to not get too general
| '{' (yield_expr | star_expressions) "="? "!" NAME [':' fstring_format_spec*] !'}' { RAISE_SYNTAX_ERROR("f-string: expecting '}'") }
| '{' (yield_expr | star_expressions) "="? ':' fstring_format_spec* !'}' { RAISE_SYNTAX_ERROR("f-string: expecting '}'") }
| '{' a='=' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before '='") }
| '{' a='!' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before '!'") }
| '{' a=':' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before ':'") }
| '{' a='}' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: valid expression required before '}'") }
| '{' !(yield_expr | star_expressions) { RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting a valid expression after '{'")}
| '{' (yield_expr | star_expressions) !('=' | '!' | ':' | '}') {
PyErr_Occurred() ? NULL : RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting '=', or '!', or ':', or '}'") }
| '{' (yield_expr | star_expressions) '=' !('!' | ':' | '}') {
PyErr_Occurred() ? NULL : RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting '!', or ':', or '}'") }
| '{' (yield_expr | star_expressions) '='? invalid_conversion_character
| '{' (yield_expr | star_expressions) '='? ['!' NAME] !(':' | '}') {
PyErr_Occurred() ? NULL : RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting ':' or '}'") }
| '{' (yield_expr | star_expressions) '='? ['!' NAME] ':' fstring_format_spec* !'}' {
PyErr_Occurred() ? NULL : RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting '}', or format specs") }
| '{' (yield_expr | star_expressions) '='? ['!' NAME] !'}' {
PyErr_Occurred() ? NULL : RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: expecting '}'") }

invalid_conversion_character:
| a="!" &(':'|'}') { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: missed conversion character") }
| a="!" !NAME { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "f-string: invalid conversion character") }
| '!' &(':' | '}') { RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: missing conversion character") }
| '!' !NAME { RAISE_SYNTAX_ERROR_ON_NEXT_TOKEN("f-string: invalid conversion character") }
2 changes: 1 addition & 1 deletion Lib/test/test_cmd_line_script.py
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Expand Up @@ -638,7 +638,7 @@ def test_syntaxerror_multi_line_fstring(self):
[
b' foo = f"""{}',
b' ^',
b'SyntaxError: f-string: empty expression not allowed',
b'SyntaxError: f-string: valid expression required before \'}\'',
],
)

Expand Down
73 changes: 45 additions & 28 deletions Lib/test/test_fstring.py
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Expand Up @@ -693,15 +693,13 @@ def test_format_specifier_expressions(self):
self.assertEqual(f'{10:#{3 != {4:5} and width}x}', ' 0xa')
self.assertEqual(f'result: {value:{width:{0}}.{precision:1}}', 'result: 12.35')

self.assertAllRaise(SyntaxError,
"""f-string: invalid conversion character 'r{"': """
"""expected 's', 'r', or 'a'""",
self.assertAllRaise(SyntaxError, "f-string: expecting ':' or '}'",
["""f'{"s"!r{":10"}}'""",

# This looks like a nested format spec.
])

self.assertAllRaise(SyntaxError, "f-string: invalid syntax",
self.assertAllRaise(SyntaxError,
"f-string: expecting a valid expression after '{'",
[# Invalid syntax inside a nested spec.
"f'{4:{/5}}'",
])
Expand All @@ -724,7 +722,8 @@ def __format__(self, spec):
self.assertEqual(f'{x} {x}', '1 2')

def test_missing_expression(self):
self.assertAllRaise(SyntaxError, 'f-string: empty expression not allowed',
self.assertAllRaise(SyntaxError,
"f-string: valid expression required before '}'",
["f'{}'",
"f'{ }'"
"f' {} '",
Expand All @@ -736,8 +735,8 @@ def test_missing_expression(self):
"f'''{\t\f\r\n}'''",
])

# Different error messages are raised when a specifier ('!', ':' or '=') is used after an empty expression
self.assertAllRaise(SyntaxError, "f-string: expression required before '!'",
self.assertAllRaise(SyntaxError,
"f-string: valid expression required before '!'",
["f'{!r}'",
"f'{ !r}'",
"f'{!}'",
Expand All @@ -758,15 +757,17 @@ def test_missing_expression(self):
"f'{ !xr:a}'",
])

self.assertAllRaise(SyntaxError, "f-string: expression required before ':'",
self.assertAllRaise(SyntaxError,
"f-string: valid expression required before ':'",
["f'{:}'",
"f'{ :!}'",
"f'{:2}'",
"f'''{\t\f\r\n:a}'''",
"f'{:'",
])

self.assertAllRaise(SyntaxError, "f-string: expression required before '='",
self.assertAllRaise(SyntaxError,
"f-string: valid expression required before '='",
["f'{=}'",
"f'{ =}'",
"f'{ =:}'",
Expand All @@ -784,21 +785,18 @@ def test_missing_expression(self):
def test_parens_in_expressions(self):
self.assertEqual(f'{3,}', '(3,)')

# Add these because when an expression is evaluated, parens
# are added around it. But we shouldn't go from an invalid
# expression to a valid one. The added parens are just
# supposed to allow whitespace (including newlines).
self.assertAllRaise(SyntaxError, 'invalid syntax',
self.assertAllRaise(SyntaxError,
"f-string: expecting a valid expression after '{'",
["f'{,}'",
"f'{,}'", # this is (,), which is an error
])

self.assertAllRaise(SyntaxError, r"f-string: unmatched '\)'",
["f'{3)+(4}'",
])

def test_newlines_before_syntax_error(self):
self.assertAllRaise(SyntaxError, "invalid syntax",
self.assertAllRaise(SyntaxError,
"f-string: expecting a valid expression after '{'",
["f'{.}'", "\nf'{.}'", "\n\nf'{.}'"])

def test_backslashes_in_string_part(self):
Expand Down Expand Up @@ -885,7 +883,8 @@ def test_backslashes_in_expression_part(self):
self.assertEqual(f'{"\N{LEFT CURLY BRACKET}"}', '{')
self.assertEqual(rf'{"\N{LEFT CURLY BRACKET}"}', '{')

self.assertAllRaise(SyntaxError, 'empty expression not allowed',
self.assertAllRaise(SyntaxError,
"f-string: valid expression required before '}'",
["f'{\n}'",
])

Expand Down Expand Up @@ -930,9 +929,23 @@ def test_lambda(self):
self.assertEqual(f'{(lambda y:x*y)("8"):10}', "88888 ")

# lambda doesn't work without parens, because the colon
# makes the parser think it's a format_spec
self.assertAllRaise(SyntaxError, 'invalid syntax',
# makes the parser think it's a format_spec
# emit warning if we can match a format_spec
self.assertAllRaise(SyntaxError,
"f-string: lambda expressions are not allowed "
"without parentheses",
["f'{lambda x:x}'",
"f'{lambda :x}'",
"f'{lambda *arg, :x}'",
"f'{1, lambda:x}'",
])

# but don't emit the paren warning in general cases
self.assertAllRaise(SyntaxError,
"f-string: expecting a valid expression after '{'",
["f'{lambda x:}'",
"f'{lambda :}'",
"f'{+ lambda:None}'",
])

def test_valid_prefixes(self):
Expand Down Expand Up @@ -1185,7 +1198,7 @@ def test_conversions(self):
"f'{3!g'",
])

self.assertAllRaise(SyntaxError, 'f-string: missed conversion character',
self.assertAllRaise(SyntaxError, 'f-string: missing conversion character',
["f'{3!}'",
"f'{3!:'",
"f'{3!:}'",
Expand Down Expand Up @@ -1244,8 +1257,7 @@ def test_mismatched_braces(self):
])

self.assertAllRaise(SyntaxError, "f-string: expecting '}'",
["f'{3:{{>10}'",
"f'{3'",
["f'{3'",
"f'{3!'",
"f'{3:'",
"f'{3!s'",
Expand All @@ -1261,6 +1273,11 @@ def test_mismatched_braces(self):
"f'{i='", # See gh-93418.
])

self.assertAllRaise(SyntaxError,
"f-string: expecting a valid expression after '{'",
["f'{3:{{>10}'",
])

# But these are just normal strings.
self.assertEqual(f'{"{"}', '{')
self.assertEqual(f'{"}"}', '}')
Expand Down Expand Up @@ -1481,7 +1498,8 @@ def test_walrus(self):
self.assertEqual(x, 10)

def test_invalid_syntax_error_message(self):
with self.assertRaisesRegex(SyntaxError, "invalid syntax"):
with self.assertRaisesRegex(SyntaxError,
"f-string: expecting '=', or '!', or ':', or '}'"):
compile("f'{a $ b}'", "?", "exec")

def test_with_two_commas_in_format_specifier(self):
Expand All @@ -1505,12 +1523,11 @@ def test_with_an_underscore_and_a_comma_in_format_specifier(self):
f'{1:_,}'

def test_syntax_error_for_starred_expressions(self):
error_msg = re.escape("can't use starred expression here")
with self.assertRaisesRegex(SyntaxError, error_msg):
with self.assertRaisesRegex(SyntaxError, "can't use starred expression here"):
compile("f'{*a}'", "?", "exec")

error_msg = re.escape("invalid syntax")
with self.assertRaisesRegex(SyntaxError, error_msg):
with self.assertRaisesRegex(SyntaxError,
"f-string: expecting a valid expression after '{'"):
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compile("f'{**a}'", "?", "exec")

if __name__ == '__main__':
Expand Down
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