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bpo-38870: Implement a precedence algorithm in ast.unparse (GH-17377)

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Implement a simple precedence algorithm for ast.unparse in order to avoid redundant
parenthesis for nested structures in the final output.
This commit is contained in:
Batuhan Taşkaya 2020-03-01 23:12:17 +03:00 • committed by GitHub
parent 185903de12
commit 397b96f6d7
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3 changed files with 172 additions and 16 deletions
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41
Lib/test/test_unparse.py
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@ -125,6 +125,13 @@ class ASTTestCase(unittest.TestCase):
def check_invalid(self, node, raises=ValueError):
self.assertRaises(raises, ast.unparse, node)
def check_src_roundtrip(self, code1, code2=None, strip=True):
code2 = code2 or code1
code1 = ast.unparse(ast.parse(code1))
if strip:
code1 = code1.strip()
self.assertEqual(code2, code1)
class UnparseTestCase(ASTTestCase):
# Tests for specific bugs found in earlier versions of unparse
@ -281,6 +288,40 @@ class UnparseTestCase(ASTTestCase):
def test_invalid_yield_from(self):
self.check_invalid(ast.YieldFrom(value=None))
class CosmeticTestCase(ASTTestCase):
"""Test if there are cosmetic issues caused by unnecesary additions"""
def test_simple_expressions_parens(self):
self.check_src_roundtrip("(a := b)")
self.check_src_roundtrip("await x")
self.check_src_roundtrip("x if x else y")
self.check_src_roundtrip("lambda x: x")
self.check_src_roundtrip("1 + 1")
self.check_src_roundtrip("1 + 2 / 3")
self.check_src_roundtrip("(1 + 2) / 3")
self.check_src_roundtrip("(1 + 2) * 3 + 4 * (5 + 2)")
self.check_src_roundtrip("(1 + 2) * 3 + 4 * (5 + 2) ** 2")
self.check_src_roundtrip("~ x")
self.check_src_roundtrip("x and y")
self.check_src_roundtrip("x and y and z")
self.check_src_roundtrip("x and (y and x)")
self.check_src_roundtrip("(x and y) and z")
self.check_src_roundtrip("(x ** y) ** z ** q")
self.check_src_roundtrip("x >> y")
self.check_src_roundtrip("x << y")
self.check_src_roundtrip("x >> y and x >> z")
self.check_src_roundtrip("x + y - z * q ^ t ** k")
self.check_src_roundtrip("P * V if P and V else n * R * T")
self.check_src_roundtrip("lambda P, V, n: P * V == n * R * T")
self.check_src_roundtrip("flag & (other | foo)")
self.check_src_roundtrip("not x == y")
self.check_src_roundtrip("x == (not y)")
self.check_src_roundtrip("yield x")
self.check_src_roundtrip("yield from x")
self.check_src_roundtrip("call((yield x))")
self.check_src_roundtrip("return x + (yield x)")
class DirectoryTestCase(ASTTestCase):
"""Test roundtrip behaviour on all files in Lib and Lib/test."""