feat: support for tools in OpenAIChatGenerator (#8666)

* move chatmsg>openai conversion to chatmsg dataclass

* implementation and tests cleanup

* release note

* try fixing azure chat generator

* add serde test for toolinvoker

* small fix

Author: anakin87

haystack/components/generators/chat/azure.py

@@ -142,6 +142,11 @@ def __init__(  # pylint: disable=too-many-positional-arguments
         self.max_retries = max_retries or int(os.environ.get("OPENAI_MAX_RETRIES", 5))
         self.default_headers = default_headers or {}
 
+        # This ChatGenerator does not yet supports tools. The following workaround ensures that we do not
+        # get an error when invoking the run method of the parent class (OpenAIChatGenerator).
+        self.tools = None
+        self.tools_strict = False
+
         self.client = AzureOpenAI(
             api_version=api_version,
             azure_endpoint=azure_endpoint,

haystack/components/generators/chat/hugging_face_api.py

@@ -163,10 +163,9 @@ def __init__(  # pylint: disable=too-many-positional-arguments
             msg = f"Unknown api_type {api_type}"
             raise ValueError(msg)
 
-        if tools:
-            if streaming_callback is not None:
-                raise ValueError("Using tools and streaming at the same time is not supported. Please choose one.")
-            _check_duplicate_tool_names(tools)
+        if tools and streaming_callback is not None:
+            raise ValueError("Using tools and streaming at the same time is not supported. Please choose one.")
+        _check_duplicate_tool_names(tools)
 
         # handle generation kwargs setup
         generation_kwargs = generation_kwargs.copy() if generation_kwargs else {}
@@ -241,10 +240,9 @@ def run(
         formatted_messages = [convert_message_to_hf_format(message) for message in messages]
 
         tools = tools or self.tools
-        if tools:
-            if self.streaming_callback:
-                raise ValueError("Using tools and streaming at the same time is not supported. Please choose one.")
-            _check_duplicate_tool_names(tools)
+        if tools and self.streaming_callback:
+            raise ValueError("Using tools and streaming at the same time is not supported. Please choose one.")
+        _check_duplicate_tool_names(tools)
 
         if self.streaming_callback:
             return self._run_streaming(formatted_messages, generation_kwargs)

haystack/components/generators/chat/openai.py

@@ -9,7 +9,6 @@
 from openai.types.chat import ChatCompletion, ChatCompletionChunk
 
 from haystack import component, default_from_dict, default_to_dict, logging
-from haystack.components.generators.openai_utils import _convert_message_to_openai_format
 from haystack.dataclasses import ChatMessage, StreamingChunk
 from haystack.utils import Secret, deserialize_callable, deserialize_secrets_inplace, serialize_callable
 
@@ -207,7 +206,7 @@ def run(
         streaming_callback = streaming_callback or self.streaming_callback
 
         # adapt ChatMessage(s) to the format expected by the OpenAI API
-        openai_formatted_messages = [_convert_message_to_openai_format(message) for message in messages]
+        openai_formatted_messages = [message.to_openai_dict_format() for message in messages]
 
         completion: Union[Stream[ChatCompletionChunk], ChatCompletion] = self.client.chat.completions.create(
             model=self.model,

haystack/components/generators/openai.py

@@ -2,6 +2,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+import json
 import warnings
 from dataclasses import asdict, dataclass, field
 from enum import Enum
@@ -381,3 +382,47 @@ def from_dict(cls, data: Dict[str, Any]) -> "ChatMessage":
         data["_content"] = content
 
         return cls(**data)
+
+    def to_openai_dict_format(self) -> Dict[str, Any]:
+        """
+        Convert a ChatMessage to the dictionary format expected by OpenAI's Chat API.
+        """
+        text_contents = self.texts
+        tool_calls = self.tool_calls
+        tool_call_results = self.tool_call_results
+
+        if not text_contents and not tool_calls and not tool_call_results:
+            raise ValueError(
+                "A `ChatMessage` must contain at least one `TextContent`, `ToolCall`, or `ToolCallResult`."
+            )
+        if len(text_contents) + len(tool_call_results) > 1:
+            raise ValueError("A `ChatMessage` can only contain one `TextContent` or one `ToolCallResult`.")
+
+        openai_msg: Dict[str, Any] = {"role": self._role.value}
+
+        if tool_call_results:
+            result = tool_call_results[0]
+            if result.origin.id is None:
+                raise ValueError("`ToolCall` must have a non-null `id` attribute to be used with OpenAI.")
+            openai_msg["content"] = result.result
+            openai_msg["tool_call_id"] = result.origin.id
+            # OpenAI does not provide a way to communicate errors in tool invocations, so we ignore the error field
+            return openai_msg
+
+        if text_contents:
+            openai_msg["content"] = text_contents[0]
+        if tool_calls:
+            openai_tool_calls = []
+            for tc in tool_calls:
+                if tc.id is None:
+                    raise ValueError("`ToolCall` must have a non-null `id` attribute to be used with OpenAI.")
+                openai_tool_calls.append(
+                    {
+                        "id": tc.id,
+                        "type": "function",
+                        # We disable ensure_ascii so special chars like emojis are not converted
+                        "function": {"name": tc.tool_name, "arguments": json.dumps(tc.arguments, ensure_ascii=False)},
+                    }
+                )
+            openai_msg["tool_calls"] = openai_tool_calls
+        return openai_msg

haystack/components/generators/openai_utils.py

@@ -216,13 +216,15 @@ def _remove_title_from_schema(schema: Dict[str, Any]):
                 del property_schema[key]
 
 
-def _check_duplicate_tool_names(tools: List[Tool]) -> None:
+def _check_duplicate_tool_names(tools: Optional[List[Tool]]) -> None:
     """
-    Check for duplicate tool names and raises a ValueError if they are found.
+    Checks for duplicate tool names and raises a ValueError if they are found.
 
     :param tools: The list of tools to check.
     :raises ValueError: If duplicate tool names are found.
     """
+    if tools is None:
+        return
     tool_names = [tool.name for tool in tools]
     duplicate_tool_names = {name for name in tool_names if tool_names.count(name) > 1}
     if duplicate_tool_names:

haystack/dataclasses/chat_message.py

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Add support for Tools in the OpenAI Chat Generator.

haystack/dataclasses/tool.py

@@ -17,6 +17,14 @@ def streaming_callback_handler(x):
     return x
 
 
+@pytest.fixture
+def chat_messages():
+    return [
+        ChatMessage.from_system("You are a helpful assistant speaking A2 level of English"),
+        ChatMessage.from_user("Tell me about Berlin"),
+    ]
+
+
 @pytest.fixture
 def model_info_mock():
     with patch(