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| 1 # -*- coding: utf-8 -*- |
| 2 """ |
| 3 jinja2.optimizer |
| 4 ~~~~~~~~~~~~~~~~ |
| 5 |
| 6 The jinja optimizer is currently trying to constant fold a few expressions |
| 7 and modify the AST in place so that it should be easier to evaluate it. |
| 8 |
| 9 Because the AST does not contain all the scoping information and the |
| 10 compiler has to find that out, we cannot do all the optimizations we |
| 11 want. For example loop unrolling doesn't work because unrolled loops would |
| 12 have a different scoping. |
| 13 |
| 14 The solution would be a second syntax tree that has the scoping rules stored
. |
| 15 |
| 16 :copyright: (c) 2010 by the Jinja Team. |
| 17 :license: BSD. |
| 18 """ |
| 19 from jinja2 import nodes |
| 20 from jinja2.visitor import NodeTransformer |
| 21 |
| 22 |
| 23 def optimize(node, environment): |
| 24 """The context hint can be used to perform an static optimization |
| 25 based on the context given.""" |
| 26 optimizer = Optimizer(environment) |
| 27 return optimizer.visit(node) |
| 28 |
| 29 |
| 30 class Optimizer(NodeTransformer): |
| 31 |
| 32 def __init__(self, environment): |
| 33 self.environment = environment |
| 34 |
| 35 def visit_If(self, node): |
| 36 """Eliminate dead code.""" |
| 37 # do not optimize ifs that have a block inside so that it doesn't |
| 38 # break super(). |
| 39 if node.find(nodes.Block) is not None: |
| 40 return self.generic_visit(node) |
| 41 try: |
| 42 val = self.visit(node.test).as_const() |
| 43 except nodes.Impossible: |
| 44 return self.generic_visit(node) |
| 45 if val: |
| 46 body = node.body |
| 47 else: |
| 48 body = node.else_ |
| 49 result = [] |
| 50 for node in body: |
| 51 result.extend(self.visit_list(node)) |
| 52 return result |
| 53 |
| 54 def fold(self, node): |
| 55 """Do constant folding.""" |
| 56 node = self.generic_visit(node) |
| 57 try: |
| 58 return nodes.Const.from_untrusted(node.as_const(), |
| 59 lineno=node.lineno, |
| 60 environment=self.environment) |
| 61 except nodes.Impossible: |
| 62 return node |
| 63 |
| 64 visit_Add = visit_Sub = visit_Mul = visit_Div = visit_FloorDiv = \ |
| 65 visit_Pow = visit_Mod = visit_And = visit_Or = visit_Pos = visit_Neg = \ |
| 66 visit_Not = visit_Compare = visit_Getitem = visit_Getattr = visit_Call = \ |
| 67 visit_Filter = visit_Test = visit_CondExpr = fold |
| 68 del fold |
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