core[patch]: fix xml output parser transform (#19530)

Previous PR passed _parser attribute which apparently is not meant to be
used by user code and causes non deterministic failures on CI when
testing the transform and a transform methods. Reverting this change
temporarily.

libs/core/langchain_core/output_parsers/xml.py

@@ -1,7 +1,6 @@
 import re
 from typing import Any, AsyncIterator, Dict, Iterator, List, Optional, Union
 from xml.etree import ElementTree as ET
-from xml.etree.ElementTree import TreeBuilder
 
 from langchain_core.exceptions import OutputParserException
 from langchain_core.messages import BaseMessage
@@ -61,13 +60,7 @@ class XMLOutputParser(BaseTransformOutputParser):
     def _transform(
         self, input: Iterator[Union[str, BaseMessage]]
     ) -> Iterator[AddableDict]:
-        # Imports are temporarily placed here to avoid issue with caching on CI
-        # likely if you're reading this you can move them to the top of the file
-        from defusedxml.ElementTree import DefusedXMLParser  # type: ignore[import]
-
-        parser = ET.XMLPullParser(
-            ["start", "end"], _parser=DefusedXMLParser(target=TreeBuilder())
-        )
+        parser = ET.XMLPullParser(["start", "end"])
         xml_start_re = re.compile(r"<[a-zA-Z:_]")
         xml_started = False
         current_path: List[str] = []
@@ -117,12 +110,7 @@ class XMLOutputParser(BaseTransformOutputParser):
     async def _atransform(
         self, input: AsyncIterator[Union[str, BaseMessage]]
     ) -> AsyncIterator[AddableDict]:
-        # Imports are temporarily placed here to avoid issue with caching on CI
-        # likely if you're reading this you can move them to the top of the file
-        from defusedxml.ElementTree import DefusedXMLParser  # type: ignore[import]
-
-        _parser = DefusedXMLParser(target=TreeBuilder())
-        parser = ET.XMLPullParser(["start", "end"], _parser=_parser)
+        parser = ET.XMLPullParser(["start", "end"])
         xml_start_re = re.compile(r"<[a-zA-Z:_]")
         xml_started = False
         current_path: List[str] = []

libs/core/tests/unit_tests/output_parsers/test_xml_parser.py

@@ -1,6 +1,5 @@
 """Test XMLOutputParser"""
 from typing import AsyncIterator
-from xml.etree.ElementTree import ParseError
 
 import pytest
 
@@ -100,17 +99,3 @@ async def tests_billion_laughs_attack() -> None:
 
     with pytest.raises(OutputParserException):
         await parser.aparse(MALICIOUS_XML)
-
-    with pytest.raises(ParseError):
-        # Right now raises undefined entity error
-        assert list(parser.transform(iter(MALICIOUS_XML))) == [
-            {"foo": [{"bar": [{"baz": None}]}]}
-        ]
-
-    async def _as_iter(string: str) -> AsyncIterator[str]:
-        for c in string:
-            yield c
-
-    with pytest.raises(ParseError):
-        chunks = [chunk async for chunk in parser.atransform(_as_iter(MALICIOUS_XML))]
-        assert chunks == [{"foo": [{"bar": [{"baz": None}]}]}]