chore: improve select_streaming_callback type hints

haystack/components/generators/chat/hugging_face_api.py

@@ -8,8 +8,16 @@
 
 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 ChatMessage, ComponentInfo, StreamingChunk, ToolCall, select_streaming_callback
-from haystack.dataclasses.streaming_chunk import StreamingCallbackT
+from haystack.dataclasses import (
+    AsyncStreamingCallbackT,
+    ChatMessage,
+    ComponentInfo,
+    StreamingCallbackT,
+    StreamingChunk,
+    SyncStreamingCallbackT,
+    ToolCall,
+    select_streaming_callback,
+)
 from haystack.lazy_imports import LazyImport
 from haystack.tools import (
     Tool,
@@ -437,7 +445,10 @@ async def run_async(
         return await self._run_non_streaming_async(formatted_messages, generation_kwargs, hf_tools)
 
     def _run_streaming(
-        self, messages: List[Dict[str, str]], generation_kwargs: Dict[str, Any], streaming_callback: StreamingCallbackT
+        self,
+        messages: List[Dict[str, str]],
+        generation_kwargs: Dict[str, Any],
+        streaming_callback: SyncStreamingCallbackT,
     ):
         api_output: Iterable[ChatCompletionStreamOutput] = self._client.chat_completion(
             messages,
@@ -501,7 +512,10 @@ def _run_non_streaming(
         return {"replies": [message]}
 
     async def _run_streaming_async(
-        self, messages: List[Dict[str, str]], generation_kwargs: Dict[str, Any], streaming_callback: StreamingCallbackT
+        self,
+        messages: List[Dict[str, str]],
+        generation_kwargs: Dict[str, Any],
+        streaming_callback: AsyncStreamingCallbackT,
     ):
         api_output: AsyncIterable[ChatCompletionStreamOutput] = await self._async_client.chat_completion(
             messages,

haystack/components/generators/chat/hugging_face_local.py

@@ -11,7 +11,7 @@
 from typing import Any, Callable, Dict, List, Literal, Optional, Union, cast
 
 from haystack import component, default_from_dict, default_to_dict, logging
-from haystack.dataclasses import ChatMessage, ComponentInfo, StreamingCallbackT, ToolCall
+from haystack.dataclasses import AsyncStreamingCallbackT, ChatMessage, ComponentInfo, StreamingCallbackT, ToolCall
 from haystack.dataclasses.streaming_chunk import select_streaming_callback
 from haystack.lazy_imports import LazyImport
 from haystack.tools import (
@@ -566,7 +566,7 @@ async def _run_streaming_async(  # pylint: disable=too-many-positional-arguments
         tokenizer: Union["PreTrainedTokenizer", "PreTrainedTokenizerFast"],
         generation_kwargs: Dict[str, Any],
         stop_words: Optional[List[str]],
-        streaming_callback: StreamingCallbackT,
+        streaming_callback: AsyncStreamingCallbackT,
     ):
         """
         Handles async streaming generation of responses.
@@ -588,7 +588,9 @@ async def _run_streaming_async(  # pylint: disable=too-many-positional-arguments
         # get the component name and type
         component_info = ComponentInfo.from_component(self)
 
-        async_handler = AsyncHFTokenStreamingHandler(tokenizer, streaming_callback, stop_words, component_info)  # type: ignore
+        async_handler = AsyncHFTokenStreamingHandler(
+            tokenizer=tokenizer, stream_handler=streaming_callback, stop_words=stop_words, component_info=component_info
+        )
         generation_kwargs["streamer"] = async_handler
 
         # Start queue processing in the background

haystack/components/generators/chat/openai.py

@@ -280,8 +280,10 @@ def run(
 
         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,  # type: ignore
+                streaming_callback,
             )
 
         else:
@@ -356,8 +358,10 @@ async def run_async(
 
         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,  # type: ignore
+                streaming_callback,
             )
 
         else:

haystack/components/generators/hugging_face_api.py

@@ -7,7 +7,13 @@
 from typing import Any, Dict, Iterable, List, Optional, Union, cast
 
 from haystack import component, default_from_dict, default_to_dict
-from haystack.dataclasses import ComponentInfo, StreamingCallbackT, StreamingChunk, select_streaming_callback
+from haystack.dataclasses import (
+    ComponentInfo,
+    StreamingCallbackT,
+    StreamingChunk,
+    SyncStreamingCallbackT,
+    select_streaming_callback,
+)
 from haystack.lazy_imports import LazyImport
 from haystack.utils import Secret, deserialize_callable, deserialize_secrets_inplace, serialize_callable
 from haystack.utils.hf import HFGenerationAPIType, HFModelType, check_valid_model
@@ -214,13 +220,13 @@ def run(
         )
 
         if streaming_callback is not None:
-            return self._stream_and_build_response(hf_output, streaming_callback)
+            return self._stream_and_build_response(hf_output=hf_output, streaming_callback=streaming_callback)
 
         # mypy doesn't know that hf_output is a TextGenerationOutput, so we cast it
         return self._build_non_streaming_response(cast(TextGenerationOutput, hf_output))
 
     def _stream_and_build_response(
-        self, hf_output: Iterable["TextGenerationStreamOutput"], streaming_callback: StreamingCallbackT
+        self, hf_output: Iterable["TextGenerationStreamOutput"], streaming_callback: SyncStreamingCallbackT
     ):
         chunks: List[StreamingChunk] = []
         first_chunk_time = None

haystack/components/generators/hugging_face_local.py

@@ -233,6 +233,11 @@ def run(
                 "The component HuggingFaceLocalGenerator was not warmed up. Please call warm_up() before running."
             )
 
+        # at this point, we know that the pipeline has been initialized
+        assert self.pipeline is not None
+        # text-generation and text2text-generation pipelines always have a non-None tokenizer
+        assert self.pipeline.tokenizer is not None
+
         if not prompt:
             return {"replies": []}
 
@@ -254,15 +259,16 @@ def run(
                 )
                 logger.warning(msg, num_responses=num_responses)
                 updated_generation_kwargs["num_return_sequences"] = 1
+
             # streamer parameter hooks into HF streaming, HFTokenStreamingHandler is an adapter to our streaming
             updated_generation_kwargs["streamer"] = HFTokenStreamingHandler(
-                tokenizer=self.pipeline.tokenizer,  # type: ignore
+                tokenizer=self.pipeline.tokenizer,
                 stream_handler=streaming_callback,
-                stop_words=self.stop_words,  # type: ignore
+                stop_words=self.stop_words,
                 component_info=ComponentInfo.from_component(self),
             )
 
-        output = self.pipeline(prompt, stopping_criteria=self.stopping_criteria_list, **updated_generation_kwargs)  # type: ignore
+        output = self.pipeline(prompt, stopping_criteria=self.stopping_criteria_list, **updated_generation_kwargs)
         replies = [o["generated_text"] for o in output if "generated_text" in o]
 
         if self.stop_words:

haystack/components/tools/tool_invoker.py

@@ -681,11 +681,11 @@ async def run_async(
                             start=True,
                             meta={"tool_result": tool_messages[-1].tool_call_results[0].result, "tool_call": tool_call},
                         )
-                    )  # type: ignore[misc] # we have checked that streaming_callback is not None and async
+                    )
 
         # We stream one more chunk that contains a finish_reason if tool_messages were generated
         if len(tool_messages) > 0 and streaming_callback is not None:
-            await streaming_callback(StreamingChunk(content="", meta={"finish_reason": "tool_call_results"}))  # type: ignore[misc] # we have checked that streaming_callback is not None and async
+            await streaming_callback(StreamingChunk(content="", meta={"finish_reason": "tool_call_results"}))
 
         return {"tool_messages": tool_messages, "state": state}
 

haystack/dataclasses/streaming_chunk.py

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 from dataclasses import dataclass, field
-from typing import Any, Awaitable, Callable, Dict, Optional, Union
+from typing import Any, Awaitable, Callable, Dict, Literal, Optional, Union, overload
 
 from haystack.core.component import Component
 from haystack.dataclasses.chat_message import ToolCallResult
@@ -104,6 +104,20 @@ def __post_init__(self):
 StreamingCallbackT = Union[SyncStreamingCallbackT, AsyncStreamingCallbackT]
 
 
+@overload
+def select_streaming_callback(
+    init_callback: Optional[StreamingCallbackT],
+    runtime_callback: Optional[StreamingCallbackT],
+    requires_async: Literal[False],
+) -> Optional[SyncStreamingCallbackT]: ...
+@overload
+def select_streaming_callback(
+    init_callback: Optional[StreamingCallbackT],
+    runtime_callback: Optional[StreamingCallbackT],
+    requires_async: Literal[True],
+) -> Optional[AsyncStreamingCallbackT]: ...
+
+
 def select_streaming_callback(
     init_callback: Optional[StreamingCallbackT], runtime_callback: Optional[StreamingCallbackT], requires_async: bool
 ) -> Optional[StreamingCallbackT]:

haystack/utils/hf.py

@@ -5,10 +5,16 @@
 import asyncio
 import copy
 from enum import Enum
-from typing import Any, Awaitable, Callable, Dict, List, Optional, Union
+from typing import Any, Dict, List, Optional, Union
 
 from haystack import logging
-from haystack.dataclasses import ChatMessage, ComponentInfo, StreamingCallbackT, StreamingChunk
+from haystack.dataclasses import (
+    AsyncStreamingCallbackT,
+    ChatMessage,
+    ComponentInfo,
+    StreamingChunk,
+    SyncStreamingCallbackT,
+)
 from haystack.lazy_imports import LazyImport
 from haystack.utils.auth import Secret
 from haystack.utils.device import ComponentDevice
@@ -350,15 +356,15 @@ class HFTokenStreamingHandler(TextStreamer):
         Streaming handler for HuggingFaceLocalGenerator and HuggingFaceLocalChatGenerator.
 
         Note: This is a helper class for HuggingFaceLocalGenerator & HuggingFaceLocalChatGenerator enabling streaming
-        of generated text via Haystack StreamingCallbackT callbacks.
+        of generated text via Haystack SyncStreamingCallbackT callbacks.
 
         Do not use this class directly.
         """
 
         def __init__(
             self,
             tokenizer: Union[PreTrainedTokenizer, PreTrainedTokenizerFast],
-            stream_handler: StreamingCallbackT,
+            stream_handler: SyncStreamingCallbackT,
             stop_words: Optional[List[str]] = None,
             component_info: Optional[ComponentInfo] = None,
         ):
@@ -392,7 +398,7 @@ class AsyncHFTokenStreamingHandler(TextStreamer):
         def __init__(
             self,
             tokenizer: Union[PreTrainedTokenizer, PreTrainedTokenizerFast],
-            stream_handler: Callable[[StreamingChunk], Awaitable[None]],
+            stream_handler: AsyncStreamingCallbackT,
             stop_words: Optional[List[str]] = None,
             component_info: Optional[ComponentInfo] = None,
         ):