Hub Runnable (#11946)

Adds `langchain.runnables.hub.HubRunnable` for pulling configurable
objects from the hub

libs/langchain/langchain/runnables/hub.py

@@ -0,0 +1,31 @@
+from typing import Any, Optional
+
+from langchain.schema.runnable.base import Input, Output, RunnableBinding
+
+
+class HubRunnable(RunnableBinding[Input, Output]):
+    """
+    An instance of a runnable stored in the LangChain Hub.
+    """
+
+    owner_repo_commit: str
+
+    def __init__(
+        self,
+        owner_repo_commit: str,
+        *,
+        api_url: Optional[str] = None,
+        api_key: Optional[str] = None,
+        **kwargs: Any,
+    ) -> None:
+        from langchain.hub import pull
+
+        pulled = pull(owner_repo_commit, api_url=api_url, api_key=api_key)
+        super_kwargs = {
+            "kwargs": {},
+            "config": {},
+            **kwargs,
+            "bound": pulled,
+            "owner_repo_commit": owner_repo_commit,
+        }
+        super().__init__(**super_kwargs)

libs/langchain/tests/unit_tests/runnables/test_hub.py

@@ -0,0 +1,72 @@
+from typing import Any
+from unittest.mock import Mock, patch
+
+from langchain.prompts import ChatPromptTemplate
+from langchain.runnables.hub import HubRunnable
+from langchain.schema.runnable.base import ConfigurableField
+
+
+@patch("langchain.hub.pull")
+def test_hub_runnable(mock_pull: Mock) -> None:
+    mock_pull.return_value = ChatPromptTemplate.from_messages(
+        [("system", "a"), ("user", "b")]
+    )
+
+    basic: HubRunnable = HubRunnable("efriis/my-prompt")
+    bound = basic.bound
+    assert isinstance(bound, ChatPromptTemplate)
+    assert len(bound.messages) == 2
+
+
+repo_dict = {
+    "efriis/my-prompt-1": ChatPromptTemplate.from_messages(
+        [("system", "a"), ("user", "1")]
+    ),
+    "efriis/my-prompt-2": ChatPromptTemplate.from_messages(
+        [("system", "a"), ("user", "2")]
+    ),
+}
+
+
+def repo_lookup(owner_repo_commit: str, **kwargs: Any) -> ChatPromptTemplate:
+    return repo_dict[owner_repo_commit]
+
+
+@patch("langchain.hub.pull")
+def test_hub_runnable_configurable_alternative(mock_pull: Mock) -> None:
+    mock_pull.side_effect = repo_lookup
+
+    original: HubRunnable[Any, Any] = HubRunnable("efriis/my-prompt-1")
+    obj_a1 = original.configurable_alternatives(
+        ConfigurableField(id="owner_repo_commit", name="Hub ID"),
+        default_key="a1",
+        a2=HubRunnable("efriis/my-prompt-2"),
+    )
+
+    obj_a2 = obj_a1.with_config(configurable={"owner_repo_commit": "a2"})
+
+    templated = obj_a1.invoke({})
+    message_a1 = templated.messages[1]
+    assert message_a1.content == "1"
+
+    templated_2 = obj_a2.invoke({})
+    message_a2 = templated_2.messages[1]
+    assert message_a2.content == "2"
+
+
+@patch("langchain.hub.pull")
+def test_hub_runnable_configurable_fields(mock_pull: Mock) -> None:
+    mock_pull.side_effect = repo_lookup
+
+    original: HubRunnable[Any, Any] = HubRunnable("efriis/my-prompt-1")
+    obj_configurable = original.configurable_fields(
+        owner_repo_commit=ConfigurableField(id="owner_repo_commit", name="Hub ID"),
+    )
+
+    templated_1 = obj_configurable.invoke({})
+    assert templated_1.messages[1].content == "1"
+
+    templated_2 = obj_configurable.with_config(
+        configurable={"owner_repo_commit": "efriis/my-prompt-2"}
+    ).invoke({})
+    assert templated_2.messages[1].content == "2"