From 6a6dd97c52eeeedaed3a7d0c826fb96db5cf1c0b Mon Sep 17 00:00:00 2001
From: Erez Shinan <erezshin+git@gmail.com>
Date: Fri, 1 Feb 2019 14:22:47 +0200
Subject: [PATCH] VisitError now allows explicit access to previous exception
 (Issue #314)

---
 lark/exceptions.py | 7 ++++++-
 lark/visitors.py   | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lark/exceptions.py b/lark/exceptions.py
index 9a4e9a0..2534ee4 100644
--- a/lark/exceptions.py
+++ b/lark/exceptions.py
@@ -87,5 +87,10 @@ class UnexpectedToken(ParseError, UnexpectedInput):
         super(UnexpectedToken, self).__init__(message)
 
 class VisitError(Exception):
-    pass
+    def __init__(self, tree, orig_exc):
+        self.tree = tree
+        self.orig_exc = orig_exc
+
+        message = 'Error trying to process rule "%s":\n\n%s' % (tree.data, orig_exc)
+        super(VisitError, self).__init__(message)
 ###}
diff --git a/lark/visitors.py b/lark/visitors.py
index ed43c26..f89d942 100644
--- a/lark/visitors.py
+++ b/lark/visitors.py
@@ -43,7 +43,7 @@ class Transformer:
             except GrammarError:
                 raise
             except Exception as e:
-                raise VisitError('Error trying to process rule "%s":\n\n%s' % (tree.data, e))
+                raise VisitError(tree, e)
 
     def _transform_children(self, children):
         for c in children: