17760482097

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Pull #9754

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Merge 0c0073114 into e3d4e9e94

Pull Request Pull Request #9754: feat: support structured outputs in `OpenAIChatGenerator`

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haystack/components/generators/chat/openai.py

# SPDX-FileCopyrightText: 2022-present deepset GmbH <info@deepset.ai>
#
# SPDX-License-Identifier: Apache-2.0

import json
import os
from datetime import datetime
from typing import Any, Optional, Union

from openai import AsyncOpenAI, AsyncStream, OpenAI, Stream
from openai.lib._pydantic import to_strict_json_schema
from openai.types.chat import (
    ChatCompletion,
    ChatCompletionChunk,
    ChatCompletionMessage,
    ChatCompletionMessageCustomToolCall,
    ParsedChatCompletion,
    ParsedChatCompletionMessage,
)
from openai.types.chat.chat_completion import Choice
from openai.types.chat.chat_completion_chunk import Choice as ChunkChoice
from pydantic import BaseModel

from haystack import component, default_from_dict, default_to_dict, logging
from haystack.components.generators.utils import _convert_streaming_chunks_to_chat_message
from haystack.dataclasses import (
    AsyncStreamingCallbackT,
    ChatMessage,
    ComponentInfo,
    FinishReason,
    StreamingCallbackT,
    StreamingChunk,
    SyncStreamingCallbackT,
    ToolCall,
    ToolCallDelta,
    select_streaming_callback,
)
from haystack.tools import (
    Tool,
    Toolset,
    _check_duplicate_tool_names,
    deserialize_tools_or_toolset_inplace,
    serialize_tools_or_toolset,
)
from haystack.utils import Secret, deserialize_callable, deserialize_secrets_inplace, serialize_callable
from haystack.utils.http_client import init_http_client

logger = logging.getLogger(__name__)


@component
class OpenAIChatGenerator:
    """
    Completes chats using OpenAI's large language models (LLMs).

    It works with the gpt-4 and o-series models and supports streaming responses
    from OpenAI API. It uses [ChatMessage](https://docs.haystack.deepset.ai/docs/chatmessage)
    format in input and output.

    You can customize how the text is generated by passing parameters to the
    OpenAI API. Use the `**generation_kwargs` argument when you initialize
    the component or when you run it. Any parameter that works with
    `openai.ChatCompletion.create` will work here too.

    For details on OpenAI API parameters, see
    [OpenAI documentation](https://platform.openai.com/docs/api-reference/chat).

    ### Usage example

    ```python
    from haystack.components.generators.chat import OpenAIChatGenerator
    from haystack.dataclasses import ChatMessage

    messages = [ChatMessage.from_user("What's Natural Language Processing?")]

    client = OpenAIChatGenerator()
    response = client.run(messages)
    print(response)
    ```
    Output:
    ```
    {'replies':
        [ChatMessage(_role=<ChatRole.ASSISTANT: 'assistant'>, _content=
        [TextContent(text="Natural Language Processing (NLP) is a branch of artificial intelligence
            that focuses on enabling computers to understand, interpret, and generate human language in
            a way that is meaningful and useful.")],
         _name=None,
         _meta={'model': 'gpt-4o-mini', 'index': 0, 'finish_reason': 'stop',
         'usage': {'prompt_tokens': 15, 'completion_tokens': 36, 'total_tokens': 51}})
        ]
    }
    ```
    """

    def __init__(  # pylint: disable=too-many-positional-arguments
        self,
        api_key: Secret = Secret.from_env_var("OPENAI_API_KEY"),
        model: str = "gpt-4o-mini",
        streaming_callback: Optional[StreamingCallbackT] = None,
        api_base_url: Optional[str] = None,
        organization: Optional[str] = None,
        generation_kwargs: Optional[dict[str, Any]] = None,
        timeout: Optional[float] = None,
        max_retries: Optional[int] = None,
        tools: Optional[Union[list[Tool], Toolset]] = None,
        tools_strict: bool = False,
        http_client_kwargs: Optional[dict[str, Any]] = None,
    ):
        """
        Creates an instance of OpenAIChatGenerator. Unless specified otherwise in `model`, uses OpenAI's gpt-4o-mini

        Before initializing the component, you can set the 'OPENAI_TIMEOUT' and 'OPENAI_MAX_RETRIES'
        environment variables to override the `timeout` and `max_retries` parameters respectively
        in the OpenAI client.

        :param api_key: The OpenAI API key.
            You can set it with an environment variable `OPENAI_API_KEY`, or pass with this parameter
            during initialization.
        :param model: The name of the model to use.
        :param streaming_callback: A callback function that is called when a new token is received from the stream.
            The callback function accepts [StreamingChunk](https://docs.haystack.deepset.ai/docs/data-classes#streamingchunk)
            as an argument.
        :param api_base_url: An optional base URL.
        :param organization: Your organization ID, defaults to `None`. See
        [production best practices](https://platform.openai.com/docs/guides/production-best-practices/setting-up-your-organization).
        :param generation_kwargs: Other parameters to use for the model. These parameters are sent directly to
            the OpenAI endpoint. See OpenAI [documentation](https://platform.openai.com/docs/api-reference/chat) for
            more details.
            Some of the supported parameters:
            - `max_tokens`: The maximum number of tokens the output text can have.
            - `temperature`: What sampling temperature to use. Higher values mean the model will take more risks.
                Try 0.9 for more creative applications and 0 (argmax sampling) for ones with a well-defined answer.
            - `top_p`: An alternative to sampling with temperature, called nucleus sampling, where the model
                considers the results of the tokens with top_p probability mass. For example, 0.1 means only the tokens
                comprising the top 10% probability mass are considered.
            - `n`: How many completions to generate for each prompt. For example, if the LLM gets 3 prompts and n is 2,
                it will generate two completions for each of the three prompts, ending up with 6 completions in total.
            - `stop`: One or more sequences after which the LLM should stop generating tokens.
            - `presence_penalty`: What penalty to apply if a token is already present at all. Bigger values mean
                the model will be less likely to repeat the same token in the text.
            - `frequency_penalty`: What penalty to apply if a token has already been generated in the text.
                Bigger values mean the model will be less likely to repeat the same token in the text.
            - `logit_bias`: Add a logit bias to specific tokens. The keys of the dictionary are tokens, and the
                values are the bias to add to that token.
            - `response_format`: A JSON schema or a Pydantic model that enforces the structure of the model's response.
                If provided, the output will always be validated against this
                format (unless the model returns a tool call).
                For details, see the [OpenAI Structured Outputs documentation](https://platform.openai.com/docs/guides/structured-outputs).
                Notes:
                - This parameter accepts Pydantic models and JSON schemas for latest models starting from GPT-4o.
                  Older models only support basic version of structured outputs through `{"type": "json_object"}`.
                  For detailed information on JSON mode, see the [OpenAI Structured Outputs documentation](https://platform.openai.com/docs/guides/structured-outputs#json-mode).
                - For structured outputs with streaming,
                  the `response_format` must be a JSON schema and not a Pydantic model.
        :param timeout:
            Timeout for OpenAI client calls. If not set, it defaults to either the
            `OPENAI_TIMEOUT` environment variable, or 30 seconds.
        :param max_retries:
            Maximum number of retries to contact OpenAI after an internal error.
            If not set, it defaults to either the `OPENAI_MAX_RETRIES` environment variable, or set to 5.
        :param tools:
            A list of tools or a Toolset for which the model can prepare calls. This parameter can accept either a
            list of `Tool` objects or a `Toolset` instance.
        :param tools_strict:
            Whether to enable strict schema adherence for tool calls. If set to `True`, the model will follow exactly
            the schema provided in the `parameters` field of the tool definition, but this may increase latency.
        :param http_client_kwargs:
            A dictionary of keyword arguments to configure a custom `httpx.Client`or `httpx.AsyncClient`.
            For more information, see the [HTTPX documentation](https://www.python-httpx.org/api/#client).

        """
        self.api_key = api_key
        self.model = model
        self.generation_kwargs = generation_kwargs or {}
        self.streaming_callback = streaming_callback
        self.api_base_url = api_base_url
        self.organization = organization
        self.timeout = timeout
        self.max_retries = max_retries
        self.tools = tools  # Store tools as-is, whether it's a list or a Toolset
        self.tools_strict = tools_strict
        self.http_client_kwargs = http_client_kwargs
        # Check for duplicate tool names
        _check_duplicate_tool_names(list(self.tools or []))

        if timeout is None:
            timeout = float(os.environ.get("OPENAI_TIMEOUT", "30.0"))
        if max_retries is None:
            max_retries = int(os.environ.get("OPENAI_MAX_RETRIES", "5"))

        client_kwargs: dict[str, Any] = {
            "api_key": api_key.resolve_value(),
            "organization": organization,
            "base_url": api_base_url,
            "timeout": timeout,
            "max_retries": max_retries,
        }

        self.client = OpenAI(http_client=init_http_client(self.http_client_kwargs, async_client=False), **client_kwargs)
        self.async_client = AsyncOpenAI(
            http_client=init_http_client(self.http_client_kwargs, async_client=True), **client_kwargs
        )

    def _get_telemetry_data(self) -> dict[str, Any]:
        """
        Data that is sent to Posthog for usage analytics.
        """
        return {"model": self.model}

    def to_dict(self) -> dict[str, Any]:
        """
        Serialize this component to a dictionary.

        :returns:
            The serialized component as a dictionary.
        """
        callback_name = serialize_callable(self.streaming_callback) if self.streaming_callback else None
        generation_kwargs = self.generation_kwargs.copy()
        response_format = generation_kwargs.get("response_format")

        # If the response format is a Pydantic model, it's converted to openai's json schema format
        # If it's already a json schema, it's left as is
        if response_format and issubclass(response_format, BaseModel):
            json_schema = {
                "type": "json_schema",
                "json_schema": {
                    "name": response_format.__name__,
                    "strict": True,
                    "schema": to_strict_json_schema(response_format),
                },
            }
            generation_kwargs["response_format"] = json_schema

        return default_to_dict(
            self,
            model=self.model,
            streaming_callback=callback_name,
            api_base_url=self.api_base_url,
            organization=self.organization,
            generation_kwargs=generation_kwargs,
            api_key=self.api_key.to_dict(),
            timeout=self.timeout,
            max_retries=self.max_retries,
            tools=serialize_tools_or_toolset(self.tools),
            tools_strict=self.tools_strict,
            http_client_kwargs=self.http_client_kwargs,
        )

    @classmethod
    def from_dict(cls, data: dict[str, Any]) -> "OpenAIChatGenerator":
        """
        Deserialize this component from a dictionary.

        :param data: The dictionary representation of this component.
        :returns:
            The deserialized component instance.
        """
        deserialize_secrets_inplace(data["init_parameters"], keys=["api_key"])
        deserialize_tools_or_toolset_inplace(data["init_parameters"], key="tools")
        init_params = data.get("init_parameters", {})
        serialized_callback_handler = init_params.get("streaming_callback")

        if serialized_callback_handler:
            data["init_parameters"]["streaming_callback"] = deserialize_callable(serialized_callback_handler)
        return default_from_dict(cls, data)

    @component.output_types(replies=list[ChatMessage])
    def run(
        self,
        messages: list[ChatMessage],
        streaming_callback: Optional[StreamingCallbackT] = None,
        generation_kwargs: Optional[dict[str, Any]] = None,
        *,
        tools: Optional[Union[list[Tool], Toolset]] = None,
        tools_strict: Optional[bool] = None,
    ):
        """
        Invokes chat completion based on the provided messages and generation parameters.

        :param messages:
            A list of ChatMessage instances representing the input messages.
        :param streaming_callback:
            A callback function that is called when a new token is received from the stream.
        :param generation_kwargs:
            Additional keyword arguments for text generation. These parameters will
            override the parameters passed during component initialization.
            For details on OpenAI API parameters, see [OpenAI documentation](https://platform.openai.com/docs/api-reference/chat/create).
        :param tools:
            A list of tools or a Toolset for which the model can prepare calls. If set, it will override the
            `tools` parameter set during component initialization. This parameter can accept either a list of
            `Tool` objects or a `Toolset` instance.
        :param tools_strict:
            Whether to enable strict schema adherence for tool calls. If set to `True`, the model will follow exactly
            the schema provided in the `parameters` field of the tool definition, but this may increase latency.
            If set, it will override the `tools_strict` parameter set during component initialization.

        :returns:
            A dictionary with the following key:
            - `replies`: A list containing the generated responses as ChatMessage instances.
        """
        if len(messages) == 0:
            return {"replies": []}

        streaming_callback = select_streaming_callback(
            init_callback=self.streaming_callback, runtime_callback=streaming_callback, requires_async=False
        )
        chat_completion: Union[Stream[ChatCompletionChunk], ChatCompletion, ParsedChatCompletion]

        api_args = self._prepare_api_call(
            messages=messages,
            streaming_callback=streaming_callback,
            generation_kwargs=generation_kwargs,
            tools=tools,
            tools_strict=tools_strict,
        )
        openai_endpoint = api_args.pop("openai_endpoint")
        openai_endpoint_method = getattr(self.client.chat.completions, openai_endpoint)
        chat_completion = openai_endpoint_method(**api_args)

        if streaming_callback is not None:
            completions = self._handle_stream_response(
                # we cannot check isinstance(chat_completion, Stream) because some observability tools wrap Stream
                # and return a different type. See https://github.com/deepset-ai/haystack/issues/9014.
                chat_completion,  # type: ignore
                streaming_callback,
            )

        else:
            assert isinstance(chat_completion, ChatCompletion), "Unexpected response type for non-streaming request."
            completions = [
                _convert_chat_completion_to_chat_message(chat_completion, choice) for choice in chat_completion.choices
            ]

        # before returning, do post-processing of the completions
        for message in completions:
            _check_finish_reason(message.meta)

        return {"replies": completions}

    @component.output_types(replies=list[ChatMessage])
    async def run_async(
        self,
        messages: list[ChatMessage],
        streaming_callback: Optional[StreamingCallbackT] = None,
        generation_kwargs: Optional[dict[str, Any]] = None,
        *,
        tools: Optional[Union[list[Tool], Toolset]] = None,
        tools_strict: Optional[bool] = None,
    ):
        """
        Asynchronously invokes chat completion based on the provided messages and generation parameters.

        This is the asynchronous version of the `run` method. It has the same parameters and return values
        but can be used with `await` in async code.

        :param messages:
            A list of ChatMessage instances representing the input messages.
        :param streaming_callback:
            A callback function that is called when a new token is received from the stream.
            Must be a coroutine.
        :param generation_kwargs:
            Additional keyword arguments for text generation. These parameters will
            override the parameters passed during component initialization.
            For details on OpenAI API parameters, see [OpenAI documentation](https://platform.openai.com/docs/api-reference/chat/create).
        :param tools:
            A list of tools or a Toolset for which the model can prepare calls. If set, it will override the
            `tools` parameter set during component initialization. This parameter can accept either a list of
            `Tool` objects or a `Toolset` instance.
        :param tools_strict:
            Whether to enable strict schema adherence for tool calls. If set to `True`, the model will follow exactly
            the schema provided in the `parameters` field of the tool definition, but this may increase latency.
            If set, it will override the `tools_strict` parameter set during component initialization.

        :returns:
            A dictionary with the following key:
            - `replies`: A list containing the generated responses as ChatMessage instances.
        """
        # validate and select the streaming callback
        streaming_callback = select_streaming_callback(
            init_callback=self.streaming_callback, runtime_callback=streaming_callback, requires_async=True
        )
        chat_completion: Union[AsyncStream[ChatCompletionChunk], ChatCompletion, ParsedChatCompletion]

        if len(messages) == 0:
            return {"replies": []}

        api_args = self._prepare_api_call(
            messages=messages,
            streaming_callback=streaming_callback,
            generation_kwargs=generation_kwargs,
            tools=tools,
            tools_strict=tools_strict,
        )

        openai_endpoint = api_args.pop("openai_endpoint")
        openai_endpoint_method = getattr(self.async_client.chat.completions, openai_endpoint)
        chat_completion = await openai_endpoint_method(**api_args)

        if streaming_callback is not None:
            completions = await self._handle_async_stream_response(
                # we cannot check isinstance(chat_completion, AsyncStream) because some observability tools wrap
                # AsyncStream and return a different type. See https://github.com/deepset-ai/haystack/issues/9014.
                chat_completion,  # type: ignore
                streaming_callback,
            )

        else:
            assert isinstance(chat_completion, ChatCompletion), "Unexpected response type for non-streaming request."
            completions = [
                _convert_chat_completion_to_chat_message(chat_completion, choice) for choice in chat_completion.choices
            ]

        # before returning, do post-processing of the completions
        for message in completions:
            _check_finish_reason(message.meta)

        return {"replies": completions}

    def _prepare_api_call(  # noqa: PLR0913
        self,
        *,
        messages: list[ChatMessage],
        streaming_callback: Optional[StreamingCallbackT] = None,
        generation_kwargs: Optional[dict[str, Any]] = None,
        tools: Optional[Union[list[Tool], Toolset]] = None,
        tools_strict: Optional[bool] = None,
    ) -> dict[str, Any]:
        # update generation kwargs by merging with the generation kwargs passed to the run method
        generation_kwargs = {**self.generation_kwargs, **(generation_kwargs or {})}

        is_streaming = streaming_callback is not None
        num_responses = generation_kwargs.pop("n", 1)

        if is_streaming and num_responses > 1:
            raise ValueError("Cannot stream multiple responses, please set n=1.")
        response_format = generation_kwargs.pop("response_format", None)

        # adapt ChatMessage(s) to the format expected by the OpenAI API
        openai_formatted_messages = [message.to_openai_dict_format() for message in messages]

        tools = tools or self.tools
        if isinstance(tools, Toolset):
            tools = list(tools)
        tools_strict = tools_strict if tools_strict is not None else self.tools_strict
        _check_duplicate_tool_names(tools)

        openai_tools = {}
        if tools:
            tool_definitions = []
            for t in tools:
                function_spec = {**t.tool_spec}
                if tools_strict:
                    function_spec["strict"] = True
                    function_spec["parameters"]["additionalProperties"] = False
                tool_definitions.append({"type": "function", "function": function_spec})
            openai_tools = {"tools": tool_definitions}

        base_args = {
            "model": self.model,
            "messages": openai_formatted_messages,
            "n": num_responses,
            **openai_tools,
            **generation_kwargs,
        }

        if response_format and not is_streaming:
            # for structured outputs without streaming, we use openai's parse endpoint
            # Note: `stream` cannot be passed to chat.completions.parse
            # we pass a key `openai_endpoint` as a hint to the run method to use the parse endpoint
            # this key will be removed before the API call is made
            return {**base_args, "response_format": response_format, "openai_endpoint": "parse"}

        # for structured outputs with streaming, we use openai's create endpoint
        # we pass a key `openai_endpoint` as a hint to the run method to use the create endpoint
        # this key will be removed before the API call is made
        return {
            **base_args,
            "stream": streaming_callback is not None,
            "response_format": response_format,
            "openai_endpoint": "create",
        }

    def _handle_stream_response(self, chat_completion: Stream, callback: SyncStreamingCallbackT) -> list[ChatMessage]:
        component_info = ComponentInfo.from_component(self)
        chunks: list[StreamingChunk] = []
        for chunk in chat_completion:  # pylint: disable=not-an-iterable
            assert len(chunk.choices) <= 1, "Streaming responses should have at most one choice."
            chunk_delta = _convert_chat_completion_chunk_to_streaming_chunk(
                chunk=chunk, previous_chunks=chunks, component_info=component_info
            )
            chunks.append(chunk_delta)
            callback(chunk_delta)
        return [_convert_streaming_chunks_to_chat_message(chunks=chunks)]

    async def _handle_async_stream_response(
        self, chat_completion: AsyncStream, callback: AsyncStreamingCallbackT
    ) -> list[ChatMessage]:
        component_info = ComponentInfo.from_component(self)
        chunks: list[StreamingChunk] = []
        async for chunk in chat_completion:  # pylint: disable=not-an-iterable
            assert len(chunk.choices) <= 1, "Streaming responses should have at most one choice."
            chunk_delta = _convert_chat_completion_chunk_to_streaming_chunk(
                chunk=chunk, previous_chunks=chunks, component_info=component_info
            )
            chunks.append(chunk_delta)
            await callback(chunk_delta)
        return [_convert_streaming_chunks_to_chat_message(chunks=chunks)]


def _check_finish_reason(meta: dict[str, Any]) -> None:
    if meta["finish_reason"] == "length":
        logger.warning(
            "The completion for index {index} has been truncated before reaching a natural stopping point. "
            "Increase the max_tokens parameter to allow for longer completions.",
            index=meta["index"],
            finish_reason=meta["finish_reason"],
        )
    if meta["finish_reason"] == "content_filter":
        logger.warning(
            "The completion for index {index} has been truncated due to the content filter.",
            index=meta["index"],
            finish_reason=meta["finish_reason"],
        )


def _convert_chat_completion_to_chat_message(
    completion: Union[ChatCompletion, ParsedChatCompletion], choice: Choice
) -> ChatMessage:
    """
    Converts the non-streaming response from the OpenAI API to a ChatMessage.

    :param completion: The completion returned by the OpenAI API.
    :param choice: The choice returned by the OpenAI API.
    :return: The ChatMessage.
    """
    message: Union[ChatCompletionMessage, ParsedChatCompletionMessage] = choice.message
    text = message.content
    tool_calls = []
    if message.tool_calls:
        # we currently only support function tools (not custom tools)
        # https://platform.openai.com/docs/guides/function-calling#custom-tools
        openai_tool_calls = [tc for tc in message.tool_calls if not isinstance(tc, ChatCompletionMessageCustomToolCall)]
        for openai_tc in openai_tool_calls:
            arguments_str = openai_tc.function.arguments
            try:
                arguments = json.loads(arguments_str)
                tool_calls.append(ToolCall(id=openai_tc.id, tool_name=openai_tc.function.name, arguments=arguments))
            except json.JSONDecodeError:
                logger.warning(
                    "OpenAI returned a malformed JSON string for tool call arguments. This tool call "
                    "will be skipped. To always generate a valid JSON, set `tools_strict` to `True`. "
                    "Tool call ID: {_id}, Tool name: {_name}, Arguments: {_arguments}",
                    _id=openai_tc.id,
                    _name=openai_tc.function.name,
                    _arguments=arguments_str,
                )

    chat_message = ChatMessage.from_assistant(
        text=text,
        tool_calls=tool_calls,
        meta={
            "model": completion.model,
            "index": choice.index,
            "finish_reason": choice.finish_reason,
            "usage": _serialize_usage(completion.usage),
        },
    )

    return chat_message


def _convert_chat_completion_chunk_to_streaming_chunk(
    chunk: ChatCompletionChunk, previous_chunks: list[StreamingChunk], component_info: Optional[ComponentInfo] = None
) -> StreamingChunk:
    """
    Converts the streaming response chunk from the OpenAI API to a StreamingChunk.

    :param chunk: The chunk returned by the OpenAI API.
    :param previous_chunks: A list of previously received StreamingChunks.
    :param component_info: An optional `ComponentInfo` object containing information about the component that
        generated the chunk, such as the component name and type.

    :returns:
        A StreamingChunk object representing the content of the chunk from the OpenAI API.
    """
    finish_reason_mapping: dict[str, FinishReason] = {
        "stop": "stop",
        "length": "length",
        "content_filter": "content_filter",
        "tool_calls": "tool_calls",
        "function_call": "tool_calls",
    }
    # On very first chunk so len(previous_chunks) == 0, the Choices field only provides role info (e.g. "assistant")
    # Choices is empty if include_usage is set to True where the usage information is returned.
    if len(chunk.choices) == 0:
        return StreamingChunk(
            content="",
            component_info=component_info,
            # Index is None since it's only set to an int when a content block is present
            index=None,
            finish_reason=None,
            meta={
                "model": chunk.model,
                "received_at": datetime.now().isoformat(),
                "usage": _serialize_usage(chunk.usage),
            },
        )

    choice: ChunkChoice = chunk.choices[0]

    # create a list of ToolCallDelta objects from the tool calls
    if choice.delta.tool_calls:
        tool_calls_deltas = []
        for tool_call in choice.delta.tool_calls:
            function = tool_call.function
            tool_calls_deltas.append(
                ToolCallDelta(
                    index=tool_call.index,
                    id=tool_call.id,
                    tool_name=function.name if function else None,
                    arguments=function.arguments if function and function.arguments else None,
                )
            )
        chunk_message = StreamingChunk(
            content=choice.delta.content or "",
            component_info=component_info,
            # We adopt the first tool_calls_deltas.index as the overall index of the chunk.
            index=tool_calls_deltas[0].index,
            tool_calls=tool_calls_deltas,
            start=tool_calls_deltas[0].tool_name is not None,
            finish_reason=finish_reason_mapping.get(choice.finish_reason) if choice.finish_reason else None,
            meta={
                "model": chunk.model,
                "index": choice.index,
                "tool_calls": choice.delta.tool_calls,
                "finish_reason": choice.finish_reason,
                "received_at": datetime.now().isoformat(),
                "usage": _serialize_usage(chunk.usage),
            },
        )
        return chunk_message

    # On very first chunk the choice field only provides role info (e.g. "assistant") so we set index to None
    # We set all chunks missing the content field to index of None. E.g. can happen if chunk only contains finish
    # reason.
    if choice.delta.content is None or choice.delta.role is not None:
        resolved_index = None
    else:
        # We set the index to be 0 since if text content is being streamed then no tool calls are being streamed
        # NOTE: We may need to revisit this if OpenAI allows planning/thinking content before tool calls like
        #       Anthropic Claude
        resolved_index = 0
    chunk_message = StreamingChunk(
        content=choice.delta.content or "",
        component_info=component_info,
        index=resolved_index,
        # The first chunk is always a start message chunk that only contains role information, so if we reach here
        # and previous_chunks is length 1 then this is the start of text content.
        start=len(previous_chunks) == 1,
        finish_reason=finish_reason_mapping.get(choice.finish_reason) if choice.finish_reason else None,
        meta={
            "model": chunk.model,
            "index": choice.index,
            "tool_calls": choice.delta.tool_calls,
            "finish_reason": choice.finish_reason,
            "received_at": datetime.now().isoformat(),
            "usage": _serialize_usage(chunk.usage),
        },
    )
    return chunk_message


def _serialize_usage(usage):
    """Convert OpenAI usage object to serializable dict recursively"""
    if hasattr(usage, "model_dump"):
        return usage.model_dump()
    elif hasattr(usage, "__dict__"):
        return {k: _serialize_usage(v) for k, v in usage.__dict__.items() if not k.startswith("_")}
    elif isinstance(usage, dict):
        return {k: _serialize_usage(v) for k, v in usage.items()}
    elif isinstance(usage, list):
        return [_serialize_usage(item) for item in usage]
    else:
        return usage

deepset-ai / haystack / 17760482097

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