fix issue #8357 by making json backtick regex greedy (#8528)

- Description: Markdown code blocks in json response should not break
the parser
  - Issue: #8357

@baskaryan @hinthornw

libs/langchain/langchain/output_parsers/json.py

@@ -19,7 +19,7 @@ def parse_json_markdown(json_string: str) -> dict:
         The parsed JSON object as a Python dictionary.
     """
     # Try to find JSON string within triple backticks
-    match = re.search(r"```(json)?(.*?)```", json_string, re.DOTALL)
+    match = re.search(r"```(json)?(.*)```", json_string, re.DOTALL)
 
     # If no match found, assume the entire string is a JSON string
     if match is None:

libs/langchain/tests/unit_tests/output_parsers/test_json.py

@@ -54,6 +54,12 @@ TICKS_WITH_NEW_LINES_EVERYWHERE = """
 
 """
 
+JSON_WITH_MARKDOWN_CODE_BLOCK = """```json
+{
+    "foo": "```bar```"
+}
+```"""
+
 NO_TICKS = """{
     "foo": "bar"
 }"""
@@ -106,3 +112,8 @@ TEST_CASES = [
 def test_parse_json(json_string: str) -> None:
     parsed = parse_json_markdown(json_string)
     assert parsed == {"foo": "bar"}
+
+
+def test_parse_json_with_code_block() -> None:
+    parsed = parse_json_markdown(JSON_WITH_MARKDOWN_CODE_BLOCK)
+    assert parsed == {"foo": "```bar```"}