chore: consolidate outputs to state string (#11902)

haystack/tools/tool.py

@@ -380,6 +380,33 @@ def _check_duplicate_tool_names(tools: list[Tool] | None) -> None:
         raise ValueError(f"Duplicate tool names found: {duplicate_tool_names}")
 
 
+def _convert_handler(config: dict[str, Any], converter: Callable[[Any], Any]) -> dict[str, Any]:
+    """
+    Copies a single output config, converting its "handler" entry (if present) via `converter`.
+
+    :param config: A single output configuration dictionary that may contain a "handler" key.
+    :param converter: `serialize_callable` or `deserialize_callable`, applied to the "handler" value.
+    :returns: A copy of `config` with the "handler" value converted, if present.
+    """
+    new_config = config.copy()
+    if "handler" in config:
+        new_config["handler"] = converter(config["handler"])
+    return new_config
+
+
+def _convert_handler_in_configs(
+    configs: dict[str, dict[str, Any]], converter: Callable[[Any], Any]
+) -> dict[str, dict[str, Any]]:
+    """
+    Applies `_convert_handler` to every config in a dictionary of named output configs.
+
+    :param configs: A mapping of keys to output configuration dictionaries.
+    :param converter: `serialize_callable` or `deserialize_callable`, applied to each "handler" value.
+    :returns: A new mapping with the same keys, each config converted via `_convert_handler`.
+    """
+    return {key: _convert_handler(config, converter) for key, config in configs.items()}
+
+
 def _serialize_outputs_to_state(outputs_to_state: dict[str, dict[str, Any]]) -> dict[str, dict[str, Any]]:
     """
     Serializes the outputs_to_state dictionary, converting any callable handlers to their string representation.
@@ -387,13 +414,7 @@ def _serialize_outputs_to_state(outputs_to_state: dict[str, dict[str, Any]]) ->
     :param outputs_to_state: The outputs_to_state dictionary to serialize.
     :returns: The serialized outputs_to_state dictionary.
     """
-    serialized_outputs = {}
-    for key, config in outputs_to_state.items():
-        serialized_config = config.copy()
-        if "handler" in config:
-            serialized_config["handler"] = serialize_callable(config["handler"])
-        serialized_outputs[key] = serialized_config
-    return serialized_outputs
+    return _convert_handler_in_configs(outputs_to_state, serialize_callable)
 
 
 def _deserialize_outputs_to_state(outputs_to_state: dict[str, dict[str, Any]]) -> dict[str, dict[str, Any]]:
@@ -403,13 +424,7 @@ def _deserialize_outputs_to_state(outputs_to_state: dict[str, dict[str, Any]]) -
     :param outputs_to_state: The outputs_to_state dictionary to deserialize.
     :returns: The deserialized outputs_to_state dictionary.
     """
-    deserialized_outputs = {}
-    for key, config in outputs_to_state.items():
-        deserialized_config = config.copy()
-        if "handler" in config:
-            deserialized_config["handler"] = deserialize_callable(config["handler"])
-        deserialized_outputs[key] = deserialized_config
-    return deserialized_outputs
+    return _convert_handler_in_configs(outputs_to_state, deserialize_callable)
 
 
 def _serialize_outputs_to_string(outputs_to_string: dict[str, Any]) -> dict[str, Any]:
@@ -421,19 +436,10 @@ def _serialize_outputs_to_string(outputs_to_string: dict[str, Any]) -> dict[str,
     """
     if "source" in outputs_to_string or "handler" in outputs_to_string or "raw_result" in outputs_to_string:
         # Single output configuration
-        serialized_outputs = outputs_to_string.copy()
-        if "handler" in outputs_to_string:
-            serialized_outputs["handler"] = serialize_callable(outputs_to_string["handler"])
-        return serialized_outputs
+        return _convert_handler(outputs_to_string, serialize_callable)
 
     # Multiple outputs configuration
-    serialized_outputs = {}
-    for key, config in outputs_to_string.items():
-        serialized_config = config.copy()
-        if "handler" in config:
-            serialized_config["handler"] = serialize_callable(config["handler"])
-        serialized_outputs[key] = serialized_config
-    return serialized_outputs
+    return _convert_handler_in_configs(outputs_to_string, serialize_callable)
 
 
 def _deserialize_outputs_to_string(outputs_to_string: dict[str, Any]) -> dict[str, Any]:
@@ -445,16 +451,7 @@ def _deserialize_outputs_to_string(outputs_to_string: dict[str, Any]) -> dict[st
     """
     if "source" in outputs_to_string or "handler" in outputs_to_string or "raw_result" in outputs_to_string:
         # Single output configuration
-        deserialized_outputs = outputs_to_string.copy()
-        if "handler" in outputs_to_string:
-            deserialized_outputs["handler"] = deserialize_callable(outputs_to_string["handler"])
-        return deserialized_outputs
+        return _convert_handler(outputs_to_string, deserialize_callable)
 
     # Multiple outputs configuration
-    deserialized_outputs = {}
-    for key, config in outputs_to_string.items():
-        deserialized_config = config.copy()
-        if "handler" in config:
-            deserialized_config["handler"] = deserialize_callable(config["handler"])
-        deserialized_outputs[key] = deserialized_config
-    return deserialized_outputs
+    return _convert_handler_in_configs(outputs_to_string, deserialize_callable)

test/tools/test_tool.py

@@ -3,13 +3,19 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import re
+from typing import Any
 
 import pytest
 
 from haystack.dataclasses import TextContent
 from haystack.tools import Tool, _check_duplicate_tool_names
 from haystack.tools.errors import ToolInvocationError
-from haystack.tools.tool import _deserialize_outputs_to_string, _serialize_outputs_to_string
+from haystack.tools.tool import (
+    _deserialize_outputs_to_state,
+    _deserialize_outputs_to_string,
+    _serialize_outputs_to_state,
+    _serialize_outputs_to_string,
+)
 
 
 def get_weather_report(city: str) -> str:
@@ -248,6 +254,32 @@ class TestTool:
             "temp": {"source": "temperature", "handler": format_string},
         }
 
+    def test_serialize_outputs_to_state(self):
+        config: dict[str, dict[str, Any]] = {
+            "documents": {"source": "docs", "handler": format_string},
+            "summary": {"source": "docs", "handler": get_weather_report},
+            "raw_docs": {"source": "docs"},
+        }
+        serialized = _serialize_outputs_to_state(config)
+        assert serialized == {
+            "documents": {"source": "docs", "handler": "test_tool.format_string"},
+            "summary": {"source": "docs", "handler": "test_tool.get_weather_report"},
+            "raw_docs": {"source": "docs"},
+        }
+
+    def test_deserialize_outputs_to_state(self):
+        serialized = {
+            "documents": {"source": "docs", "handler": "test_tool.format_string"},
+            "summary": {"source": "docs", "handler": "test_tool.get_weather_report"},
+            "raw_docs": {"source": "docs"},
+        }
+        deserialized = _deserialize_outputs_to_state(serialized)
+        assert deserialized == {
+            "documents": {"source": "docs", "handler": format_string},
+            "summary": {"source": "docs", "handler": get_weather_report},
+            "raw_docs": {"source": "docs"},
+        }
+
     def test_inputs_from_state_validation_with_invalid_parameter(self):
         """Test that inputs_from_state is validated against the parameters schema"""
         with pytest.raises(