Move parser.grammar check deeper into TreeMatcher

Author: NasalDaemon

lark/reconstruct.py

@@ -3,7 +3,6 @@
 
 from typing import Dict, Callable, Iterable, Optional
 
-from .exceptions import ConfigurationError
 from .lark import Lark
 from .tree import Tree, ParseTree
 from .visitors import Transformer_InPlace
@@ -79,9 +78,6 @@ class Reconstructor(TreeMatcher):
     write_tokens: WriteTokensTransformer
 
     def __init__(self, parser: Lark, term_subs: Optional[Dict[str, Callable[[Symbol], str]]]=None) -> None:
-        if not hasattr(parser, 'grammar') and parser.options.cache:
-            raise ConfigurationError('Unanalyzed grammar not available from cached parser, use cache_grammar=True')
-
         TreeMatcher.__init__(self, parser)
 
         self.write_tokens = WriteTokensTransformer({t.name:t for t in self.tokens}, term_subs or {})

lark/tree_matcher.py

@@ -2,9 +2,11 @@
 
 import re
 from collections import defaultdict
+from copy import deepcopy
 
 from . import Tree, Token
 from .common import ParserConf
+from .exceptions import ConfigurationError
 from .parsers import earley
 from .grammar import Rule, Terminal, NonTerminal
 
@@ -89,8 +91,15 @@ class TreeMatcher:
     def __init__(self, parser):
         # XXX TODO calling compile twice returns different results!
         assert not parser.options.maybe_placeholders
+
         # XXX TODO: we just ignore the potential existence of a postlexer
-        self.tokens, rules, _extra = parser.grammar.compile(parser.options.start, set())
+        if parser.options.postlex is None:
+            self.tokens = deepcopy(parser.tokens)
+            rules = deepcopy(parser.rules)
+        else:
+            if not hasattr(parser, 'grammar') and parser.options.cache:
+                raise ConfigurationError('Unanalyzed grammar not available from cached parser, use cache_grammar=True')
+            self.tokens, rules, _extra = parser.grammar.compile(parser.options.start, set())
 
         self.rules_for_root = defaultdict(list)