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bpo-38871: Fix lib2to3 to be able to use in edge cases of filter #17780

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Merged
vstinner merged 3 commits into from
Jan 7, 2020
Merged

bpo-38871: Fix lib2to3 to be able to use in edge cases of filter #17780

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a602703
bpo-38871: Fix lib2to3 to be able to use in edge cases when handling …
corona10 Jan 1, 2020
75d1792
bpo-38871: Update NEWS.d
corona10 Jan 7, 2020
4529cb4
bpo-38871: Update NEWS.d
corona10 Jan 7, 2020
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10 changes: 7 additions & 3 deletions Lib/lib2to3/fixes/fix_filter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@
from .. import fixer_base
from ..pytree import Node
from ..pygram import python_symbols as syms
from ..fixer_util import Name, ArgList, ListComp, in_special_context
from ..fixer_util import Name, ArgList, ListComp, in_special_context, parenthesize


class FixFilter(fixer_base.ConditionalFix):
Expand Down Expand Up @@ -65,10 +65,14 @@ def transform(self, node, results):
trailers.append(t.clone())

if "filter_lambda" in results:
xp = results.get("xp").clone()
if xp.type == syms.test:
xp.prefix = ""
xp = parenthesize(xp)

new = ListComp(results.get("fp").clone(),
results.get("fp").clone(),
results.get("it").clone(),
results.get("xp").clone())
results.get("it").clone(), xp)
new = Node(syms.power, [new] + trailers, prefix="")

elif "none" in results:
Expand Down
5 changes: 5 additions & 0 deletions Lib/lib2to3/tests/test_fixers.py
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Expand Up @@ -2954,6 +2954,11 @@ def test_filter_basic(self):
a = """x = [x for x in range(10) if x%2 == 0]"""
self.check(b, a)

# bpo-38871
b = """filter(lambda x: True if x > 2 else False, [1, 2, 3])"""
a = """[x for x in [1, 2, 3] if (True if x > 2 else False)]"""
self.check(b, a)

def test_filter_trailers(self):
b = """x = filter(None, 'abc')[0]"""
a = """x = [_f for _f in 'abc' if _f][0]"""
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2020-01-01-18-44-52.bpo-38871.3EEOLg.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Correctly parenthesize filter-based statements that contain lambda
expressions in mod:`lib2to3`. Patch by Dong-hee Na.