Experimental parser: visualize rule trees.

tools/lexer_generator/nfa_builder.py

 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 222 matching lines @@
 
   def nfa(self, graph):
     (start, end, nodes_created) = self.__nfa(graph)
     end.close(None)
     self.__compute_epsilon_closures(start)
     f = lambda node, state: self.__replace_catch_all(self.__encoding, node)
     Automaton.visit_states(set([start]), f)
     return Nfa(self.__encoding, start, end, nodes_created)
 
   @staticmethod
+  def rule_tree_dot(graph):
+    node_ix = [0]
+    node_template = 'node [label="%s"]; N_%d;'
+    edge_template = 'N_%d -> N_%d'
+    nodes = []
+    edges = []
+
+    def escape(v):
+      v = str(v)
+      v = v.replace('\r', '\\\\r').replace('\t', '\\\\t').replace('\n', '\\\\n')
+      v = v.replace('\\', '\\\\').replace('\"', '\\\"')
+      return v
+
+    def process_thing(thing):
+      if isinstance(thing, str):
+        node_ix[0] += 1
+        nodes.append(node_template % (escape(thing), node_ix[0]))
+        return node_ix[0]
+      if isinstance(thing, tuple):
+        child_ixs = map(process_thing, list(thing)[1:])
+        node_ix[0] += 1
+        nodes.append(node_template % (escape(thing[0]), node_ix[0]))
+        for child_ix in child_ixs:
+          edges.append(edge_template % (node_ix[0], child_ix))
+        return node_ix[0]
+      if isinstance(thing, Action):
+        node_ix[0] += 1
+        nodes.append(node_template % (str(thing), node_ix[0]))
+        return node_ix[0]
+      raise Exception
+
+    process_thing(graph)
+    return 'digraph { %s %s }' % ('\n'.join(nodes), '\n'.join(edges))
+
+  @staticmethod
   def add_action(graph, action):
     return ('ACTION', graph, action)
 
   @staticmethod
   def add_continue(graph):
     return ('CONTINUE', graph)
 
   @staticmethod
   def catch_all():
     return ('CATCH_ALL',)
@@ skipping 16 matching lines @@
 
   __modifer_map = {
     '+': 'ONE_OR_MORE',
     '?': 'ZERO_OR_ONE',
     '*': 'ZERO_OR_MORE',
   }
 
   @staticmethod
   def apply_modifier(modifier, graph):
     return (NfaBuilder.__modifer_map[modifier], graph)