1 files changed, 40 insertions, 0 deletions
diff --git a/src/jinja2/optimizer.py b/src/jinja2/optimizer.py
new file mode 100644
index 00000000..39d059f1
--- /dev/null
+++ b/src/jinja2/optimizer.py
@@ -0,0 +1,40 @@
+"""The optimizer tries to constant fold expressions and modify the AST
+in place so that it should be faster to evaluate.
+
+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 scope. The solution would be a second syntax tree
+that stored the scoping rules.
+"""
+from . import nodes
+from .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 generic_visit(self, node, *args, **kwargs):
+        node = super().generic_visit(node, *args, **kwargs)
+
+        # Do constant folding. Some other nodes besides Expr have
+        # as_const, but folding them causes errors later on.
+        if isinstance(node, nodes.Expr):
+            try:
+                return nodes.Const.from_untrusted(
+                    node.as_const(args[0] if args else None),
+                    lineno=node.lineno,
+                    environment=self.environment,
+                )
+            except nodes.Impossible:
+                pass
+
+        return node