Fix LALR shift/reduce warnings when debug=True (Issue #258)

lark/grammar.py

@@ -46,7 +46,7 @@ class Rule(object):
         self.options = options
 
     def __str__(self):
-        return '<%s : %s>' % (self.origin, ' '.join(map(str,self.expansion)))
+        return '<%s : %s>' % (self.origin.name, ' '.join(x.name for x in self.expansion))
 
     def __repr__(self):
         return 'Rule(%r, %r, %r, %r)' % (self.origin, self.expansion, self.alias, self.options)

lark/parser_frontends.py

@@ -39,12 +39,14 @@ class WithLexer:
 
 class LALR_TraditionalLexer(WithLexer):
     def __init__(self, lexer_conf, parser_conf, options=None):
-        self.parser = lalr_parser.Parser(parser_conf)
+        debug = options.debug if options else False
+        self.parser = lalr_parser.Parser(parser_conf, debug=debug)
         self.init_traditional_lexer(lexer_conf)
 
 class LALR_ContextualLexer(WithLexer):
     def __init__(self, lexer_conf, parser_conf, options=None):
-        self.parser = lalr_parser.Parser(parser_conf)
+        debug = options.debug if options else False
+        self.parser = lalr_parser.Parser(parser_conf, debug=debug)
         self.init_contextual_lexer(lexer_conf)
 
 class LALR_CustomLexer(WithLexer):

lark/parsers/grammar_analysis.py

@@ -14,9 +14,9 @@ class RulePtr(object):
         self.index = index
 
     def __repr__(self):
-        before = self.rule.expansion[:self.index]
-        after = self.rule.expansion[self.index:]
-        return '<%s : %s * %s>' % (self.rule.origin, ' '.join(before), ' '.join(after))
+        before = [x.name for x in self.rule.expansion[:self.index]]
+        after = [x.name for x in self.rule.expansion[self.index:]]
+        return '<%s : %s * %s>' % (self.rule.origin.name, ' '.join(before), ' '.join(after))
 
     @property
     def next(self):

lark/parsers/lalr_analysis.py

@@ -82,7 +82,9 @@ class LALR_Analyzer(GrammarAnalyzer):
             for k, v in lookahead.items():
                 if len(v) > 1:
                     if self.debug:
-                        logging.warn("Shift/reduce conflict for %s: %s. Resolving as shift.", k, v)
+                        logging.warn("Shift/reduce conflict for terminal %s:  (resolving as shift)", k.name)
+                        for act, arg in v:
+                            logging.warn(' * %s: %s', act, arg)
                     for x in v:
                         # XXX resolving shift/reduce into shift, like PLY
                         # Give a proper warning

lark/parsers/lalr_parser.py

@@ -8,10 +8,10 @@ from ..lexer import Token
 from .lalr_analysis import LALR_Analyzer, Shift
 
 class Parser:
-    def __init__(self, parser_conf):
+    def __init__(self, parser_conf, debug=False):
         assert all(r.options is None or r.options.priority is None
                    for r in parser_conf.rules), "LALR doesn't yet support prioritization"
-        analysis = LALR_Analyzer(parser_conf)
+        analysis = LALR_Analyzer(parser_conf, debug=debug)
         analysis.compute_lookahead()
         callbacks = {rule: getattr(parser_conf.callback, rule.alias or rule.origin, None)
                           for rule in parser_conf.rules}