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