fix: HuggingFaceAPIGenerator - use forward references (#8502)

* hf API generator: forward references + refactor

* release note

haystack/components/generators/hugging_face_api.py

@@ -204,37 +204,40 @@ def run(
         # check if streaming_callback is passed
         streaming_callback = streaming_callback or self.streaming_callback
 
-        stream = streaming_callback is not None
-        response = self._client.text_generation(prompt, details=True, stream=stream, **generation_kwargs)
+        hf_output = self._client.text_generation(
+            prompt, details=True, stream=streaming_callback is not None, **generation_kwargs
+        )
+
+        if streaming_callback is not None:
+            return self._stream_and_build_response(hf_output, streaming_callback)
 
-        output = self._get_stream_response(response, streaming_callback) if stream else self._get_response(response)  # type: ignore
-        return output
+        return self._build_non_streaming_response(hf_output)
 
-    def _get_stream_response(
-        self, response: Iterable[TextGenerationStreamOutput], streaming_callback: Callable[[StreamingChunk], None]
+    def _stream_and_build_response(
+        self, hf_output: Iterable["TextGenerationStreamOutput"], streaming_callback: Callable[[StreamingChunk], None]
     ):
         chunks: List[StreamingChunk] = []
-        for chunk in response:
+        for chunk in hf_output:
             token: TextGenerationOutputToken = chunk.token
             if token.special:
                 continue
             chunk_metadata = {**asdict(token), **(asdict(chunk.details) if chunk.details else {})}
             stream_chunk = StreamingChunk(token.text, chunk_metadata)
             chunks.append(stream_chunk)
-            streaming_callback(stream_chunk)  # type: ignore # streaming_callback is not None (verified in the run method)
+            streaming_callback(stream_chunk)
         metadata = {
             "finish_reason": chunks[-1].meta.get("finish_reason", None),
             "model": self._client.model,
             "usage": {"completion_tokens": chunks[-1].meta.get("generated_tokens", 0)},
         }
         return {"replies": ["".join([chunk.content for chunk in chunks])], "meta": [metadata]}
 
-    def _get_response(self, response: TextGenerationOutput):
+    def _build_non_streaming_response(self, hf_output: "TextGenerationOutput"):
         meta = [
             {
                 "model": self._client.model,
-                "finish_reason": response.details.finish_reason if response.details else None,
-                "usage": {"completion_tokens": len(response.details.tokens) if response.details else 0},
+                "finish_reason": hf_output.details.finish_reason if hf_output.details else None,
+                "usage": {"completion_tokens": len(hf_output.details.tokens) if hf_output.details else 0},
             }
         ]
-        return {"replies": [response.generated_text], "meta": meta}
+        return {"replies": [hf_output.generated_text], "meta": meta}

releasenotes/notes/hfapigen-forwardref-5c06090282557195.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Use forward references for Hugging Face Hub types in the `HuggingFaceAPIGenerator` component
+    to prevent import errors.