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# copyright 2003-2015 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of astroid.
#
# astroid is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# astroid is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with astroid. If not, see <http://www.gnu.org/licenses/>.
"""Small AST optimizations."""
import _ast
from astroid import nodes
__all__ = ('ASTPeepholeOptimizer', )
try:
_TYPES = (_ast.Str, _ast.Bytes)
except AttributeError:
_TYPES = (_ast.Str, )
class ASTPeepholeOptimizer(object):
"""Class for applying small optimizations to generate new AST."""
def optimize_binop(self, node):
"""Optimize BinOps with string Const nodes on the lhs.
This fixes an infinite recursion crash, where multiple
strings are joined using the addition operator. With a
sufficient number of such strings, astroid will fail
with a maximum recursion limit exceeded. The
function will return a Const node with all the strings
already joined.
Return ``None`` if no AST node can be obtained
through optimization.
"""
ast_nodes = []
current = node
while isinstance(current, _ast.BinOp):
# lhs must be a BinOp with the addition operand.
if not isinstance(current.left, _ast.BinOp):
return
if (not isinstance(current.left.op, _ast.Add)
or not isinstance(current.op, _ast.Add)):
return
# rhs must a str / bytes.
if not isinstance(current.right, _TYPES):
return
ast_nodes.append(current.right.s)
current = current.left
if (isinstance(current, _ast.BinOp)
and isinstance(current.left, _TYPES)
and isinstance(current.right, _TYPES)):
# Stop early if we are at the last BinOp in
# the operation
ast_nodes.append(current.right.s)
ast_nodes.append(current.left.s)
break
if not ast_nodes:
return
# If we have inconsistent types, bail out.
known = type(ast_nodes[0])
if any(type(element) is not known
for element in ast_nodes[1:]):
return
value = known().join(reversed(ast_nodes))
newnode = nodes.Const(value)
return newnode