Adjust merge logic

libs/langchain/langchain/schema/runnable/base.py

@@ -1527,6 +1527,13 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     def lc_namespace(self) -> List[str]:
         return self.__class__.__module__.split(".")[:-1]
 
+    def _merge_config(self, config: Optional[RunnableConfig]) -> RunnableConfig:
+        copy = cast(RunnableConfig, dict(self.config))
+        if config:
+            for key in config:
+                copy[key] = config[key] or copy.get(key)
+        return copy
+
     def bind(self, **kwargs: Any) -> Runnable[Input, Output]:
         return self.__class__(
             bound=self.bound, config=self.config, kwargs={**self.kwargs, **kwargs}
@@ -1552,7 +1559,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> Output:
         return self.bound.invoke(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         )
 
@@ -1564,7 +1571,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> Output:
         return await self.bound.ainvoke(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         )
 
@@ -1576,13 +1583,10 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> List[Output]:
         configs = cast(
             List[RunnableConfig],
-            [{**self.config, **(conf or {})} for conf in config]
+            [self._merge_config(conf) for conf in config]
             if isinstance(config, list)
             else [
-                patch_config(
-                    cast(RunnableConfig, {**self.config, **(config or {})}),
-                    deep_copy_locals=True,
-                )
+                patch_config(self._merge_config(config), deep_copy_locals=True)
                 for _ in range(len(inputs))
             ],
         )
@@ -1596,13 +1600,10 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> List[Output]:
         configs = cast(
             List[RunnableConfig],
-            [{**self.config, **(conf or {})} for conf in config]
+            [self._merge_config(conf) for conf in config]
             if isinstance(config, list)
             else [
-                patch_config(
-                    cast(RunnableConfig, {**self.config, **(config or {})}),
-                    deep_copy_locals=True,
-                )
+                patch_config(self._merge_config(config), deep_copy_locals=True)
                 for _ in range(len(inputs))
             ],
         )
@@ -1616,7 +1617,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> Iterator[Output]:
         yield from self.bound.stream(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         )
 
@@ -1628,7 +1629,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> AsyncIterator[Output]:
         async for item in self.bound.astream(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         ):
             yield item
@@ -1641,7 +1642,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> Iterator[Output]:
         yield from self.bound.transform(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         )
 
@@ -1653,7 +1654,7 @@ class RunnableBinding(Serializable, Runnable[Input, Output]):
     ) -> AsyncIterator[Output]:
         async for item in self.bound.atransform(
             input,
-            cast(RunnableConfig, {**self.config, **(config or {})}),
+            self._merge_config(config),
             **{**self.kwargs, **kwargs},
         ):
             yield item

libs/langchain/tests/unit_tests/schema/runnable/test_runnable.py

@@ -1,6 +1,7 @@
 from operator import itemgetter
 from typing import Any, Dict, List, Optional, Union
 from uuid import UUID
+from langchain.callbacks.tracers.stdout import ConsoleCallbackHandler
 
 import pytest
 from freezegun import freeze_time
@@ -123,6 +124,25 @@ async def test_with_config(mocker: MockerFixture) -> None:
     ]
     spy.reset_mock()
 
+    fake_1 = RunnablePassthrough()
+    fake_2 = RunnablePassthrough()
+    spy_seq_step = mocker.spy(fake_1.__class__, "invoke")
+
+    sequence = fake_1.with_config(tags=["a-tag"]) | fake_2.with_config(
+        tags=["b-tag"], max_concurrency=5
+    )
+    assert sequence.invoke("hello") == "hello"
+    assert len(spy_seq_step.call_args_list) == 2
+    for i, call in enumerate(spy_seq_step.call_args_list):
+        assert call.args[1] == "hello"
+        if i == 0:
+            assert call.args[2].get("tags") == ["a-tag"]
+            assert call.args[2].get("max_concurrency") is None
+        else:
+            assert call.args[2].get("tags") == ["b-tag"]
+            assert call.args[2].get("max_concurrency") == 5
+    spy_seq_step.reset_mock()
+
     assert [
         *fake.with_config(tags=["a-tag"]).stream(
             "hello", dict(metadata={"key": "value"})
@@ -161,14 +181,15 @@ async def test_with_config(mocker: MockerFixture) -> None:
         assert call.args[1].get("metadata") == {"a": "b"}
     spy.reset_mock()
 
+    handler = ConsoleCallbackHandler()
     assert (
         await fake.with_config(metadata={"a": "b"}).ainvoke(
-            "hello", config={"callbacks": []}
+            "hello", config={"callbacks": [handler]}
         )
         == 5
     )
     assert spy.call_args_list == [
-        mocker.call("hello", dict(callbacks=[], metadata={"a": "b"})),
+        mocker.call("hello", dict(callbacks=[handler], metadata={"a": "b"})),
     ]
     spy.reset_mock()