Improvements to puppet + other small stuff

examples/calc.py

@@ -53,7 +53,10 @@ class CalculateTree(Transformer):
         return value
 
     def var(self, name):
-        return self.vars[name]
+        try:
+            return self.vars[name]
+        except KeyError:
+            raise Exception("Variable not found: %s" % name)
 
 
 calc_parser = Lark(calc_grammar, parser='lalr', transformer=CalculateTree())

lark/parsers/lalr_puppet.py

@@ -4,6 +4,7 @@ from copy import deepcopy
 
 from .lalr_analysis import Shift, Reduce
 from .. import Token
+from ..exceptions import ParseError
 
 
 class ParserPuppet(object):
@@ -32,7 +33,8 @@ class ParserPuppet(object):
 
         state = state_stack[-1]
         action, arg = self.parser.parse_table.states[state][token.type]
-        assert arg != end_state
+        if arg == end_state:
+            raise ParseError(arg)
 
         while action is Reduce:
             rule = arg
@@ -56,7 +58,10 @@ class ParserPuppet(object):
                 return self.result
 
             state = state_stack[-1]
-            action, arg = self.parser.parse_table.states[state][token.type]
+            try:
+                action, arg = self.parser.parse_table.states[state][token.type]
+            except KeyError as e:
+                raise ParseError(e)
             assert arg != end_state
 
         assert action is Shift
@@ -111,13 +116,14 @@ class ParserPuppet(object):
     def accepts(self):
         accepts = set()
         for t in self.choices():
-            new_puppet = self.copy()
-            try:
-                new_puppet.feed_token(Token(t, ''))
-            except KeyError:
-                pass
-            else:
-                accepts.add(t)
+            if t.isupper(): # is terminal?
+                new_puppet = self.copy()
+                try:
+                    new_puppet.feed_token(Token(t, ''))
+                except ParseError:
+                    pass
+                else:
+                    accepts.add(t)
         return accepts
 
     def resume_parse(self):

lark/utils.py

@@ -39,6 +39,14 @@ def _deserialize(data, namespace, memo):
 
 
 class Serialize(object):
+    """Safe-ish serialization interface that doesn't rely on Pickle
+
+    Attributes:
+        __serialize_fields__ (List[str]): Fields (aka attributes) to serialize.
+        __serialize_namespace__ (list): List of classes that deserialization is allowed to instanciate.
+                                        Should include all field types that aren't builtin types.
+    """
+
     def memo_serialize(self, types_to_memoize):
         memo = SerializeMemoizer(types_to_memoize)
         return self.serialize(memo), memo.serialize()
@@ -78,6 +86,8 @@ class Serialize(object):
 
 
 class SerializeMemoizer(Serialize):
+    "A version of serialize that memoizes objects to reduce space"
+
     __serialize_fields__ = 'memoized',
 
     def __init__(self, types_to_memoize):