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Unified Diff: third_party/jinja2/visitor.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/visitor.py
diff --git a/third_party/jinja2/visitor.py b/third_party/jinja2/visitor.py
new file mode 100644
index 0000000000000000000000000000000000000000..413e7c309dc7fc137aa16c24808e9acd8227aad4
--- /dev/null
+++ b/third_party/jinja2/visitor.py
@@ -0,0 +1,87 @@
+# -*- coding: utf-8 -*-
+"""
+ jinja2.visitor
+ ~~~~~~~~~~~~~~
+
+ This module implements a visitor for the nodes.
+
+ :copyright: (c) 2010 by the Jinja Team.
+ :license: BSD.
+"""
+from jinja2.nodes import Node
+
+
+class NodeVisitor(object):
+ """Walks the abstract syntax tree and call visitor functions for every
+ node found. The visitor functions may return values which will be
+ forwarded by the `visit` method.
+
+ Per default the visitor functions for the nodes are ``'visit_'`` +
+ class name of the node. So a `TryFinally` node visit function would
+ be `visit_TryFinally`. This behavior can be changed by overriding
+ the `get_visitor` function. If no visitor function exists for a node
+ (return value `None`) the `generic_visit` visitor is used instead.
+ """
+
+ def get_visitor(self, node):
+ """Return the visitor function for this node or `None` if no visitor
+ exists for this node. In that case the generic visit function is
+ used instead.
+ """
+ method = 'visit_' + node.__class__.__name__
+ return getattr(self, method, None)
+
+ def visit(self, node, *args, **kwargs):
+ """Visit a node."""
+ f = self.get_visitor(node)
+ if f is not None:
+ return f(node, *args, **kwargs)
+ return self.generic_visit(node, *args, **kwargs)
+
+ def generic_visit(self, node, *args, **kwargs):
+ """Called if no explicit visitor function exists for a node."""
+ for node in node.iter_child_nodes():
+ self.visit(node, *args, **kwargs)
+
+
+class NodeTransformer(NodeVisitor):
+ """Walks the abstract syntax tree and allows modifications of nodes.
+
+ The `NodeTransformer` will walk the AST and use the return value of the
+ visitor functions to replace or remove the old node. If the return
+ value of the visitor function is `None` the node will be removed
+ from the previous location otherwise it's replaced with the return
+ value. The return value may be the original node in which case no
+ replacement takes place.
+ """
+
+ def generic_visit(self, node, *args, **kwargs):
+ for field, old_value in node.iter_fields():
+ if isinstance(old_value, list):
+ new_values = []
+ for value in old_value:
+ if isinstance(value, Node):
+ value = self.visit(value, *args, **kwargs)
+ if value is None:
+ continue
+ elif not isinstance(value, Node):
+ new_values.extend(value)
+ continue
+ new_values.append(value)
+ old_value[:] = new_values
+ elif isinstance(old_value, Node):
+ new_node = self.visit(old_value, *args, **kwargs)
+ if new_node is None:
+ delattr(node, field)
+ else:
+ setattr(node, field, new_node)
+ return node
+
+ def visit_list(self, node, *args, **kwargs):
+ """As transformers may return lists in some places this method
+ can be used to enforce a list as return value.
+ """
+ rv = self.visit(node, *args, **kwargs)
+ if not isinstance(rv, list):
+ rv = [rv]
+ return rv
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