Give parso refactoring tools

parso/grammar.py

@@ -13,6 +13,7 @@ from parso.python.parser import Parser as PythonParser
 from parso.python.errors import ErrorFinderConfig
 from parso.python import pep8
 from parso.file_io import FileIO, KnownContentFileIO
+from parso.normalizer import RefactoringNormalizer
 
 _loaded_grammars = {}
 
@@ -170,6 +171,9 @@ class Grammar(object):
 
         return self._get_normalizer_issues(node, self._error_normalizer_config)
 
+    def refactor(self, base_node, node_to_str_map):
+        return RefactoringNormalizer(node_to_str_map).walk(base_node)
+
     def _get_normalizer(self, normalizer_config):
         if normalizer_config is None:
             normalizer_config = self._default_normalizer_config

parso/normalizer.py

@@ -12,6 +12,9 @@ class _NormalizerMeta(type):
 
 
 class Normalizer(use_metaclass(_NormalizerMeta)):
+    _rule_type_instances = {}
+    _rule_value_instances = {}
+
     def __init__(self, grammar, config):
         self.grammar = grammar
         self._config = config
@@ -181,3 +184,20 @@ class Rule(object):
         if self.is_issue(node):
             issue_node = self.get_node(node)
             self.add_issue(issue_node)
+
+
+class RefactoringNormalizer(Normalizer):
+    def __init__(self, node_to_str_map):
+        self._node_to_str_map = node_to_str_map
+
+    def visit(self, node):
+        try:
+            return self._node_to_str_map[node]
+        except KeyError:
+            return super(RefactoringNormalizer, self).visit(node)
+
+    def visit_leaf(self, leaf):
+        try:
+            return self._node_to_str_map[leaf]
+        except KeyError:
+            return super(RefactoringNormalizer, self).visit_leaf(leaf)