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Unified Diff: third_party/jinja2/optimizer.py

Issue 14761007: Add Python templating engine Jinja2 to third_party (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Created 7 years, 7 months ago
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Index: third_party/jinja2/optimizer.py
diff --git a/third_party/jinja2/optimizer.py b/third_party/jinja2/optimizer.py
new file mode 100644
index 0000000000000000000000000000000000000000..00eab115e1c19a86bb1ec64b7cf626fbf413e126
--- /dev/null
+++ b/third_party/jinja2/optimizer.py
@@ -0,0 +1,68 @@
+# -*- 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
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