68 lines
2.2 KiB
Python
68 lines
2.2 KiB
Python
# -*- coding: utf-8 -*-
|
|
"""
|
|
jinja2.optimizer
|
|
~~~~~~~~~~~~~~~~
|
|
|
|
The jinja optimizer is currently trying to constant fold a few expressions
|
|
and modify the AST in place so that it should be easier to evaluate it.
|
|
|
|
Because the AST does not contain all the scoping information and the
|
|
compiler has to find that out, we cannot do all the optimizations we
|
|
want. For example loop unrolling doesn't work because unrolled loops would
|
|
have a different scoping.
|
|
|
|
The solution would be a second syntax tree that has the scoping rules stored.
|
|
|
|
:copyright: (c) 2010 by the Jinja Team.
|
|
:license: BSD.
|
|
"""
|
|
from jinja2 import nodes
|
|
from jinja2.visitor import NodeTransformer
|
|
|
|
|
|
def optimize(node, environment):
|
|
"""The context hint can be used to perform an static optimization
|
|
based on the context given."""
|
|
optimizer = Optimizer(environment)
|
|
return optimizer.visit(node)
|
|
|
|
|
|
class Optimizer(NodeTransformer):
|
|
|
|
def __init__(self, environment):
|
|
self.environment = environment
|
|
|
|
def visit_If(self, node):
|
|
"""Eliminate dead code."""
|
|
# do not optimize ifs that have a block inside so that it doesn't
|
|
# break super().
|
|
if node.find(nodes.Block) is not None:
|
|
return self.generic_visit(node)
|
|
try:
|
|
val = self.visit(node.test).as_const()
|
|
except nodes.Impossible:
|
|
return self.generic_visit(node)
|
|
if val:
|
|
body = node.body
|
|
else:
|
|
body = node.else_
|
|
result = []
|
|
for node in body:
|
|
result.extend(self.visit_list(node))
|
|
return result
|
|
|
|
def fold(self, node):
|
|
"""Do constant folding."""
|
|
node = self.generic_visit(node)
|
|
try:
|
|
return nodes.Const.from_untrusted(node.as_const(),
|
|
lineno=node.lineno,
|
|
environment=self.environment)
|
|
except nodes.Impossible:
|
|
return node
|
|
|
|
visit_Add = visit_Sub = visit_Mul = visit_Div = visit_FloorDiv = \
|
|
visit_Pow = visit_Mod = visit_And = visit_Or = visit_Pos = visit_Neg = \
|
|
visit_Not = visit_Compare = visit_Getitem = visit_Getattr = visit_Call = \
|
|
visit_Filter = visit_Test = visit_CondExpr = fold
|
|
del fold
|