GeezerVison is showing github.com — bpo-27494: Fix a 2to3 parser bug (trailing comma) by jstasiak · Pull Request #60 · python/cpython
bpo-27494: Fix a 2to3 parser bug (trailing comma)
#60
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Expand Up
@@ -130,8 +130,8 @@ atom: ('(' [yield_expr|testlist_gexp] ')' |
'{' [dictsetmaker] '}' |
'`' testlist1 '`' |
NAME | NUMBER | STRING+ | '.' '.' '.')
listmaker: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] )
testlist_gexp: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] )
listmaker: (test|star_expr) ( old_comp_for | (',' (test|star_expr))* [','] )
testlist_gexp: (test|star_expr) ( old_comp_for | (',' (test|star_expr))* [','] )
lambdef: 'lambda' [varargslist] ':' test
trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
subscriptlist: subscript (',' subscript)* [',']
Expand Down
Expand Up
@@ -161,9 +161,28 @@ argument: ( test [comp_for] |
star_expr )
comp_iter: comp_for | comp_if
comp_for: [ASYNC] 'for' exprlist 'in' testlist_safe [comp_iter]
comp_for: [ASYNC] 'for' exprlist 'in' or_test [comp_iter]
comp_if: 'if' old_test [comp_iter]
# See note above regarding testlist_safe to see why testlist_safe is
# necessary. Unfortunately we can't use it indiscriminately in all derivations
# using comp_for-like pattern because testlist_safe derivation contains
# comma which clashes with trailing comma in arglist.
#
# The above was an issue because the parser would not follow the correct derivation
# when parsing syntactically valid Python code. Since testlist_safe was created
# specifically to handle list comprehensions and generator expressions enclosed
# with parentheses it's safe to only use it in those. That avoids the issue
# mentioned above and we can parse code like set(x for x in [],).
#
# Note that the syntax supported by this set of rules is not a valid Python 3
# syntax, hence the prefix "old".
#
# See the bug report: http://bugs.python.org/issue27494
old_comp_iter: old_comp_for | old_comp_if
old_comp_for: [ASYNC] 'for' exprlist 'in' testlist_safe [old_comp_iter]
old_comp_if: 'if' old_test [old_comp_iter]
testlist1: test (',' test)*
# not used in grammar, but may appear in "node" passed from Parser to Compiler
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Expand Up
@@ -101,8 +101,8 @@ def ListComp(xp, fp, it, test=None):
test.prefix = " "
if_leaf = Leaf(token.NAME, "if")
if_leaf.prefix = " "
inner_args.append(Node(syms.comp_if , [if_leaf, test]))
inner = Node(syms.listmaker, [xp, Node(syms.comp_for , inner_args)])
inner_args.append(Node(syms.old_comp_if , [if_leaf, test]))
inner = Node(syms.listmaker, [xp, Node(syms.old_comp_for , inner_args)])
return Node(syms.atom,
[Leaf(token.LBRACE, "["),
inner,
Expand Down
Expand Up
@@ -208,6 +208,7 @@ def attr_chain(obj, attr):
next = getattr(next, attr)
p0 = """for_stmt< 'for' any 'in' node=any ':' any* >
| old_comp_for< 'for' any 'in' node=any any* >
| comp_for< 'for' any 'in' node=any any* >
"""
p1 = """
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@@ -83,6 +83,7 @@ def transform(self, node, results):
p1 = patcomp.compile_pattern(P1)
P2 = """for_stmt< 'for' any 'in' node=any ':' any* >
| old_comp_for< 'for' any 'in' node=any any* >
| comp_for< 'for' any 'in' node=any any* >
"""
p2 = patcomp.compile_pattern(P2)
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Expand Up
@@ -15,7 +15,7 @@ class FixParen(fixer_base.BaseFix):
PATTERN = """
atom< ('[' | '(')
(listmaker< any
comp_for <
old_comp_for <
'for' NAME 'in'
target=testlist_safe< any (',' any)+ [',']
>
Expand All
@@ -24,7 +24,7 @@ class FixParen(fixer_base.BaseFix):
>
|
testlist_gexp< any
comp_for <
old_comp_for <
'for' NAME 'in'
target=testlist_safe< any (',' any)+ [',']
>
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Expand Up
@@ -55,6 +55,7 @@ def transform_range(self, node, results):
p1 = patcomp.compile_pattern(P1)
P2 = """for_stmt< 'for' any 'in' node=any ':' any* >
| old_comp_for< 'for' any 'in' node=any any* >
| comp_for< 'for' any 'in' node=any any* >
| comparison< any 'in' node=any any*>
"""
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Expand Up
@@ -459,6 +459,13 @@ def test_multiline_str_literals(self):
self.validate(s)
class TestGeneratorExpressions(GrammarTest):
def test_trailing_comma_after_generator_expression_argument_works(self):
# BPO issue 27494
self.validate("set(x for x in [],)")
def diff(fn, result):
try:
with open('@', 'w') as f:
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Original file line number
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@@ -0,0 +1,2 @@
2to3 doesn't choke on a trailing comma following a generator expression
anymore.
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