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bpo-44081: improve ast.unparse() for lambdas with no parameters (GH-26000)

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Batuhan Taskaya 2021-05-15 15:55:53 +03:00 • committed by GitHub
parent 4aa63d65a9
commit e4e931a67e
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 21 additions and 5 deletions
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9
Lib/ast.py
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@ -716,9 +716,9 @@ class _Unparser(NodeVisitor):
self.maybe_newline() self.maybe_newline()
self.write(" " * self._indent + text) self.write(" " * self._indent + text)
def write(self, text): def write(self, *text):
"""Append a piece of text""" """Add new source parts"""
self._source.append(text) self._source.extend(text)
@contextmanager @contextmanager
def buffered(self, buffer = None): def buffered(self, buffer = None):
@ -1567,7 +1567,10 @@ class _Unparser(NodeVisitor):
def visit_Lambda(self, node): def visit_Lambda(self, node):
with self.require_parens(_Precedence.TEST, node): with self.require_parens(_Precedence.TEST, node):
self.write("lambda") self.write("lambda")
with self.buffered() as buffer:
self.traverse(node.args) self.traverse(node.args)
if buffer:
self.write(" ", *buffer)
self.write(": ") self.write(": ")
self.set_precedence(_Precedence.TEST, node.body) self.set_precedence(_Precedence.TEST, node.body)
self.traverse(node.body) self.traverse(node.body)

11
Lib/test/test_unparse.py
View file

@ -531,6 +531,17 @@ class CosmeticTestCase(ASTTestCase):
self.check_src_roundtrip("a[1, 2]") self.check_src_roundtrip("a[1, 2]")
self.check_src_roundtrip("a[(1, *a)]") self.check_src_roundtrip("a[(1, *a)]")
def test_lambda_parameters(self):
self.check_src_roundtrip("lambda: something")
self.check_src_roundtrip("four = lambda: 2 + 2")
self.check_src_roundtrip("lambda x: x * 2")
self.check_src_roundtrip("square = lambda n: n ** 2")
self.check_src_roundtrip("lambda x, y: x + y")
self.check_src_roundtrip("add = lambda x, y: x + y")
self.check_src_roundtrip("lambda x, y, /, z, q, *, u: None")
self.check_src_roundtrip("lambda x, *y, **z: None")
class DirectoryTestCase(ASTTestCase): class DirectoryTestCase(ASTTestCase):
"""Test roundtrip behaviour on all files in Lib and Lib/test.""" """Test roundtrip behaviour on all files in Lib and Lib/test."""

2
Misc/NEWS.d/next/Library/2021-05-09-03-26-31.bpo-44081.A-Mrto.rst Normal file
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@ -0,0 +1,2 @@
:func:`ast.unparse` now doesn't use redundant spaces to separate ``lambda``
and the ``:`` if there are no parameters.