add replicate stream (#10518)

support direct replicate streaming. cc @cbh123 @tjaffri

libs/langchain/langchain/llms/replicate.py

@@ -1,13 +1,17 @@
 from __future__ import annotations
 
 import logging
-from typing import Any, Dict, List, Optional
+from typing import TYPE_CHECKING, Any, Dict, Iterator, List, Optional
 
 from langchain.callbacks.manager import CallbackManagerForLLMRun
 from langchain.llms.base import LLM
 from langchain.pydantic_v1 import Extra, Field, root_validator
+from langchain.schema.output import GenerationChunk
 from langchain.utils import get_from_dict_or_env
 
+if TYPE_CHECKING:
+    from replicate.prediction import Prediction
+
 logger = logging.getLogger(__name__)
 
 
@@ -46,10 +50,10 @@ class Replicate(LLM):
         serializable, is excluded from serialization.
     """
 
-    streaming: bool = Field(default=False)
+    streaming: bool = False
     """Whether to stream the results."""
 
-    stop: Optional[List[str]] = Field(default=[])
+    stop: List[str] = Field(default_factory=list)
     """Stop sequences to early-terminate generation."""
 
     class Config:
@@ -97,7 +101,7 @@ class Replicate(LLM):
         """Get the identifying parameters."""
         return {
             "model": self.model,
-            **{"model_kwargs": self.model_kwargs},
+            "model_kwargs": self.model_kwargs,
         }
 
     @property
@@ -113,6 +117,63 @@ class Replicate(LLM):
         **kwargs: Any,
     ) -> str:
         """Call to replicate endpoint."""
+        if self.streaming:
+            completion: Optional[str] = None
+            for chunk in self._stream(
+                prompt, stop=stop, run_manager=run_manager, **kwargs
+            ):
+                if completion is None:
+                    completion = chunk.text
+                else:
+                    completion += chunk.text
+        else:
+            prediction = self._create_prediction(prompt, **kwargs)
+            prediction.wait()
+            if prediction.status == "failed":
+                raise RuntimeError(prediction.error)
+            completion = prediction.output
+        assert completion is not None
+        stop_conditions = stop or self.stop
+        for s in stop_conditions:
+            if s in completion:
+                completion = completion[: completion.find(s)]
+        return completion
+
+    def _stream(
+        self,
+        prompt: str,
+        stop: Optional[List[str]] = None,
+        run_manager: Optional[CallbackManagerForLLMRun] = None,
+        **kwargs: Any,
+    ) -> Iterator[GenerationChunk]:
+        prediction = self._create_prediction(prompt, **kwargs)
+        stop_conditions = stop or self.stop
+        stop_condition_reached = False
+        current_completion: str = ""
+        for output in prediction.output_iterator():
+            current_completion += output
+            # test for stop conditions, if specified
+            for s in stop_conditions:
+                if s in current_completion:
+                    prediction.cancel()
+                    stop_condition_reached = True
+                    # Potentially some tokens that should still be yielded before ending
+                    # stream.
+                    stop_index = max(output.find(s), 0)
+                    output = output[:stop_index]
+                    if not output:
+                        break
+            if output:
+                yield GenerationChunk(text=output)
+                if run_manager:
+                    run_manager.on_llm_new_token(
+                        output,
+                        verbose=self.verbose,
+                    )
+            if stop_condition_reached:
+                break
+
+    def _create_prediction(self, prompt: str, **kwargs: Any) -> Prediction:
         try:
             import replicate as replicate_python
         except ImportError:
@@ -138,29 +199,7 @@ class Replicate(LLM):
 
             self.prompt_key = input_properties[0][0]
 
-        inputs: Dict = {self.prompt_key: prompt, **self.input}
-
-        prediction = replicate_python.predictions.create(
-            version=self.version_obj, input={**inputs, **kwargs}
+        input_: Dict = {self.prompt_key: prompt, **self.input, **kwargs}
+        return replicate_python.predictions.create(
+            version=self.version_obj, input=input_
         )
-        current_completion: str = ""
-        stop_condition_reached = False
-        for output in prediction.output_iterator():
-            current_completion += output
-
-            # test for stop conditions, if specified
-            if stop:
-                for s in stop:
-                    if s in current_completion:
-                        prediction.cancel()
-                        stop_index = current_completion.find(s)
-                        current_completion = current_completion[:stop_index]
-                        stop_condition_reached = True
-                        break
-
-            if stop_condition_reached:
-                break
-
-            if self.streaming and run_manager:
-                run_manager.on_llm_new_token(output)
-        return current_completion