From f6c97e6af4d2e7e5d8e53d40860679c4b4fe34b4 Mon Sep 17 00:00:00 2001
From: Davis Chase <130488702+dev2049@users.noreply.github.com>
Date: Wed, 10 May 2023 01:07:34 -0700
Subject: [PATCH] Fix Lark import error (#4421)

Any import that touches langchain.retrievers currently requires Lark.
Here's one attempt to fix. Not very pretty, very open to other ideas.
Alternatives I thought of are 1) make Lark requirement, 2) put
everything in parser.py in the try/except. Neither sounds much better

Related to #4316, #4275
---
 langchain/chains/query_constructor/parser.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/langchain/chains/query_constructor/parser.py b/langchain/chains/query_constructor/parser.py
index 22cfc90a56..a0c7f229d9 100644
--- a/langchain/chains/query_constructor/parser.py
+++ b/langchain/chains/query_constructor/parser.py
@@ -10,7 +10,12 @@ try:
         )
     from lark import Lark, Transformer, v_args
 except ImportError:
-    pass
+
+    def v_args(*args: Any, **kwargs: Any) -> Any:  # type: ignore
+        return lambda _: None
+
+    Transformer = object  # type: ignore
+    Lark = object  # type: ignore
 
 from langchain.chains.query_constructor.ir import (
     Comparator,