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bpo-38870: Throw ValueError on invalid yield from usage #17798

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Merged
merged 1 commit into from
Jan 2, 2020
Merged

bpo-38870: Throw ValueError on invalid yield from usage #17798

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8 changes: 4 additions & 4 deletions Lib/ast.py
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Original file line number Diff line number Diff line change
Expand Up @@ -735,10 +735,10 @@ def visit_Yield(self, node):

def visit_YieldFrom(self, node):
with self.delimit("(", ")"):
self.write("yield from")
if node.value:
self.write(" ")
self.traverse(node.value)
self.write("yield from ")
if not node.value:
raise ValueError("Node can't be used without a value attribute.")
self.traverse(node.value)

def visit_Raise(self, node):
self.fill("raise")
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2 changes: 2 additions & 0 deletions Lib/test/test_unparse.py
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Expand Up @@ -278,6 +278,8 @@ def test_invalid_fstring_conversion(self):
def test_invalid_set(self):
self.check_invalid(ast.Set(elts=[]))

def test_invalid_yield_from(self):
self.check_invalid(ast.YieldFrom(value=None))

class DirectoryTestCase(ASTTestCase):
"""Test roundtrip behaviour on all files in Lib and Lib/test."""
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