Add option to RetrievalQA chains to use provided documents in call() and acall() methods

libs/langchain/langchain/chains/retrieval_qa/base.py

@@ -31,6 +31,7 @@ class BaseRetrievalQA(Chain):
     """Chain to use to combine the documents."""
     input_key: str = "query"  #: :meta private:
     output_key: str = "result"  #: :meta private:
+    documents_key: str = "from_documents"  #: :meta private:
     return_source_documents: bool = False
     """Return the source documents or not."""
 
@@ -121,6 +122,9 @@ def _call(
         If chain has 'return_source_documents' as 'True', returns
         the retrieved documents as well under the key 'source_documents'.
 
+        If 'from_documents' is passed in the inputs, chain will use those
+        instead of calling _get_docs().
+
         Example:
         .. code-block:: python
 
@@ -132,7 +136,13 @@ def _call(
         accepts_run_manager = (
             "run_manager" in inspect.signature(self._get_docs).parameters
         )
-        if accepts_run_manager:
+        from_documents = inputs.get(self.documents_key)
+        if from_documents:
+            docs = from_documents
+            for doc in docs:
+                if not isinstance(doc, Document):
+                    raise TypeError(f"{doc} is not a Document")
+        elif accepts_run_manager:
             docs = self._get_docs(question, run_manager=_run_manager)
         else:
             docs = self._get_docs(question)  # type: ignore[call-arg]
@@ -164,6 +174,9 @@ async def _acall(
         If chain has 'return_source_documents' as 'True', returns
         the retrieved documents as well under the key 'source_documents'.
 
+        If 'from_documents' is passed in the inputs, chain will use those
+        instead of calling _get_docs().
+
         Example:
         .. code-block:: python
 
@@ -175,7 +188,13 @@ async def _acall(
         accepts_run_manager = (
             "run_manager" in inspect.signature(self._aget_docs).parameters
         )
-        if accepts_run_manager:
+        from_documents = inputs.get(self.documents_key)
+        if from_documents:
+            docs = from_documents
+            for doc in docs:
+                if not isinstance(doc, Document):
+                    raise TypeError(f"{doc} is not a Document")
+        elif accepts_run_manager:
             docs = await self._aget_docs(question, run_manager=_run_manager)
         else:
             docs = await self._aget_docs(question)  # type: ignore[call-arg]