ReAct output parser changes (#13459)

llama-index-core/llama_index/core/agent/react/output_parser.py

@@ -15,7 +15,7 @@ from llama_index.core.types import BaseOutputParser
 
 def extract_tool_use(input_text: str) -> Tuple[str, str, str]:
     pattern = (
-        r"\s*Thought: (.*?)\nAction: ([a-zA-Z0-9_]+).*?\nAction Input: .*?(\{.*\})"
+        r"\s*Thought: (.*?)\n+Action: ([a-zA-Z0-9_]+).*?\n+Action Input: .*?(\{.*\})"
     )
 
     match = re.search(pattern, input_text, re.DOTALL)
@@ -97,15 +97,16 @@ class ReActOutputParser(BaseOutputParser):
                 is_streaming=is_streaming,
             )
 
+        # An "Action" should take priority over an "Answer"
+        if "Action:" in output:
+            return parse_action_reasoning_step(output)
+
         if "Answer:" in output:
             thought, answer = extract_final_response(output)
             return ResponseReasoningStep(
                 thought=thought, response=answer, is_streaming=is_streaming
             )
 
-        if "Action:" in output:
-            return parse_action_reasoning_step(output)
-
         raise ValueError(f"Could not parse output: {output}")
 
     def format(self, output: str) -> str:

llama-index-core/tests/agent/react/test_react_output_parser.py

@@ -22,6 +22,22 @@ def test_extract_tool_use() -> None:
     mock_input_text = """\
 Thought: I need to use a tool to help me answer the question.
 Action: add
+Action Input: {"a": 1, "b": 1}
+"""
+    thought, action, action_input = extract_tool_use(mock_input_text)
+    assert thought == "I need to use a tool to help me answer the question."
+    assert action == "add"
+    assert action_input == '{"a": 1, "b": 1}'
+
+
+def test_extract_tool_use_multiline() -> None:
+    mock_input_text = """\
+Thought: I need to use a tool to help me answer the question.
+
+Action: add
+
+
+
 Action Input: {"a": 1, "b": 1}
 """
     thought, action, action_input = extract_tool_use(mock_input_text)