8000 bpo-15987: Implement ast.compare · python/cpython@cfb508f · GitHub
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bpo-15987: Implement ast.compare
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‎Doc/library/ast.rst

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@@ -1748,6 +1748,17 @@ and classes for traversing abstract syntax trees:
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Added the *indent* option.
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.. function:: compare(a, b, /, *, compare_types=True, compare_fields=True, compare_attributes=False)
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Recursively compare given 2 AST nodes. If *compare_types* is ``False``, the
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field values won't be checked whether they belong to same type or not. If
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*compare_fields* is ``True``, members of ``_fields`` attribute on both node's
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type will be checked. If *compare_attributes* is ``True``, members of
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``_attributes`` attribute on both node's will be compared.
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.. versionadded:: 3.9
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.. _ast-cli:
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Command-Line Usage

‎Doc/whatsnew/3.9.rst

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@@ -167,6 +167,9 @@ that would produce an equivalent :class:`ast.AST` object when parsed.
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Added docstrings to AST nodes that contains the ASDL signature used to
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construct that node. (Contributed by Batuhan Taskaya in :issue:`39638`.)
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Added :func:`ast.compare` for comparing 2 AST node.
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(Contributed by Batuhan Taskaya in :issue:`15987`)
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asyncio
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-------
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‎Lib/ast.py

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@@ -368,6 +368,69 @@ def walk(node):
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yield node
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def compare(
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a,
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b,
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/,
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*,
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compare_types=True,
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compare_fields=True,
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compare_attributes=False,
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):
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"""
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Compares recursively given two ast nodes. If *compare_types* is False, the
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field values won't be checked whether they belong to same type or not. If
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*compare_fields* is True, members of `_fields` attribute on both node's type
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will be checked. If *compare_attributes* is True, members of `_attributes`
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attribute on both node's will be compared.
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"""
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def _compare(a, b):
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if compare_types and type(a) is not type(b):
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return False
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elif isinstance(a, AST):
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return compare(
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a,
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b,
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compare_attributes=compare_attributes,
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compare_fields=compare_fields,
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compare_types=compare_types,
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)
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elif isinstance(a, list):
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if len(a) != len(b):
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return False
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for a_item, b_item in zip(a, b):
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if not _compare(a_item, b_item):
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return False
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else:
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return True
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else:
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return a == b
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def _compare_member(member):
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for field in getattr(a, member):
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if not hasattr(a, field) and not hasattr(b, field):
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continue
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if not (hasattr(a, field) and hasattr(b, field)):
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return False
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a_field = getattr(a, field)
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b_field = getattr(b, field)
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if not _compare(a_field, b_field):
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return False
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else:
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return True
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if type(a) is not type(b):
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return False
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if compare_fields:
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if not _compare_member("_fields"):
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return False
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if compare_attributes:
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if not _compare_member("_attributes"):
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return False
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return True
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371434
class NodeVisitor(object):
372435
"""
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A node visitor base class that walks the abstract syntax tree and calls a

‎Lib/test/test_ast.py

Lines changed: 111 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,9 @@
11
import ast
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import dis
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import os
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import random
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import sys
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import tokenize
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import unittest
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import warnings
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import weakref
@@ -25,6 +27,9 @@ def to_tuple(t):
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result.append(to_tuple(getattr(t, f)))
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return tuple(result)
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STDLIB = os.path.dirname(ast.__file__)
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STDLIB_FILES = [fn for fn in os.listdir(STDLIB) if fn.endswith(".py")]
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STDLIB_FILES.extend(["test/test_grammar.py", "test/test_unpack_ex.py"])
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# These tests are compiled through "exec"
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# There should be at least one test per statement
@@ -654,6 +659,110 @@ def test_ast_asdl_signature(self):
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expressions[0] = f"expr = {ast.expr.__subclasses__()[0].__doc__}"
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self.assertCountEqual(ast.expr.__doc__.split("\n"), expressions)
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self.assertTrue(ast.compare(ast.parse("x = 10"), ast.parse("x = 10")))
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self.assertFalse(ast.compare(ast.parse("x = 10"), ast.parse("")))
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self.assertFalse(ast.compare(ast.parse("x = 10"), ast.parse("x")))
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self.assertFalse(
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ast.compare(ast.parse("x = 10;y = 20"), ast.parse("class C:pass"))
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)
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def test_compare_literals(self):
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constants = (
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-20,
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20,
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20.0,
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1,
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1.0,
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True,
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0,
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False,
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frozenset(),
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tuple(),
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"ABCD",
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"abcd",
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"中文字",
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1e1000,
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-1e1000,
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)
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for next_index, constant in enumerate(constants[:-1], 1):
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next_constant = constants[next_index]
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with self.subTest(literal=constant, next_literal=next_constant):
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self.assertTrue(
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ast.compare(ast.Constant(constant), ast.Constant(constant))
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)
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self.assertFalse(
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ast.compare(
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ast.Constant(constant), ast.Constant(next_constant)
696+
)
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)
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same_looking_literal_cases = [
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{1, 1.0, True, 1 + 0j},
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{0, 0.0, False, 0 + 0j},
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]
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for same_looking_literals in same_looking_literal_cases:
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for literal in same_looking_literals:
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for same_looking_literal in same_looking_literals - {literal}:
706+
self.assertFalse(
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ast.compare(
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ast.Constant(literal),
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ast.Constant(same_looking_literal),
710+
)
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)
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def test_compare_fieldless(self):
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self.assertTrue(ast.compare(ast.Add(), ast.Add()))
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self.assertFalse(ast.compare(ast.Sub(), ast.Add()))
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self.assertFalse(ast.compare(ast.Sub(), ast.Constant()))
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def test_compare_stdlib(self):
719+
if support.is_resource_enabled("cpu"):
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files = STDLIB_FILES
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else:
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files = random.sample(STDLIB_FILES, 10)
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for module in files:
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with self.subTest(module):
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fn = os.path.join(STDLIB, module)
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with tokenize.open(fn) as fp:
728+
source = fp.read()
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a = ast.parse(source, fn)
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b = ast.parse(source, fn)
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self.assertTrue(
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ast.compare(a, b), f"{ast.dump(a)} != {ast.dump(b)}"
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)
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def test_compare_tests(self):
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for mode, sources in (
737+
("exec", exec_tests),
738+
("eval", eval_tests),
739+
("single", single_tests),
740+
):
741+
for source in sources:
742+
a = ast.parse(source, mode=mode)
743+
b = ast.parse(source, mode=mode)
744+
self.assertTrue(
745+
ast.compare(a, b), f"{ast.dump(a)} != {ast.dump(b)}"
746+
)
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def test_compare_options(self):
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def parse(a, b):
750+
return ast.parse(a), ast.parse(b)
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a, b = parse("2 + 2", "2+2")
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self.assertTrue(ast.compare(a, b, compare_attributes=False))
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self.assertFalse(ast.compare(a, b, compare_attributes=True))
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a, b = parse("1", "1.0")
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self.assertTrue(ast.compare(a, b, compare_types=False))
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self.assertFalse(ast.compare(a, b, compare_types=True))
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760+
a, b = parse("1", "2")
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self.assertTrue(ast.compare(a, b, compare_fields=False, compare_attributes=False))
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self.assertTrue(ast.compare(a, b, compare_fields=False, compare_attributes=True))
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self.assertFalse(ast.compare(a, b, compare_fields=True, compare_attributes=False))
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self.assertFalse(ast.compare(a, b, compare_fields=True, compare_attributes=True))
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658767
class ASTHelpers_Test(unittest.TestCase):
659768
maxDiff = None
@@ -1369,12 +1478,9 @@ def test_nameconstant(self):
13691478
self.expr(ast.NameConstant(4))
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13711480
def test_stdlib_validates(self):
1372-
stdlib = os.path.dirname(ast.__file__)
1373-
tests = [fn for fn in os.listdir(stdlib) if fn.endswith(".py")]
1374-
tests.extend(["test/test_grammar.py", "test/test_unpack_ex.py"])
1375-
for module in tests:
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for module in STDLIB_FILES:
13761482
with self.subTest(module):
1377-
fn = os.path.join(stdlib, module)
1483+
fn = os.path.join(STDLIB, module)
13781484
with open(fn, "r", encoding="utf-8") as fp:
13791485
source = fp.read()
13801486
mod = ast.parse(source, fn)

‎Misc/NEWS.d/next/Library/2020-03-28-21-00-54.bpo-15987.aBL8XS.rst

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@@ -0,0 +1,2 @@
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Implemented :func:`ast.compare` for comparing 2 AST node. Patch by Batuhan
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Taskaya.

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