Ensure that configurable fields with enums support deduplication (#11909)

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libs/langchain/langchain/schema/runnable/configurable.py

@@ -14,6 +14,7 @@ from typing import (
     Union,
     cast,
 )
+from weakref import WeakValueDictionary
 
 from langchain.pydantic_v1 import BaseModel
 from langchain.schema.runnable.base import Runnable, RunnableSerializable
@@ -262,6 +263,14 @@ class StrEnum(str, enum.Enum):
     pass
 
 
+_enums_for_spec: WeakValueDictionary[
+    Union[
+        ConfigurableFieldSingleOption, ConfigurableFieldMultiOption, ConfigurableField
+    ],
+    Type[StrEnum],
+] = WeakValueDictionary()
+
+
 class RunnableConfigurableAlternatives(DynamicRunnable[Input, Output]):
     which: ConfigurableField
 
@@ -271,10 +280,14 @@ class RunnableConfigurableAlternatives(DynamicRunnable[Input, Output]):
 
     @property
     def config_specs(self) -> Sequence[ConfigurableFieldSpec]:
-        which_enum = StrEnum(  # type: ignore[call-overload]
-            self.which.name or self.which.id,
-            ((v, v) for v in list(self.alternatives.keys()) + [self.default_key]),
-        )
+        if which_enum := _enums_for_spec.get(self.which):
+            pass
+        else:
+            which_enum = StrEnum(  # type: ignore[call-overload]
+                self.which.name or self.which.id,
+                ((v, v) for v in list(self.alternatives.keys()) + [self.default_key]),
+            )
+            _enums_for_spec[self.which] = cast(Type[StrEnum], which_enum)
         return [
             ConfigurableFieldSpec(
                 id=self.which.id,
@@ -312,10 +325,14 @@ def make_options_spec(
     spec: Union[ConfigurableFieldSingleOption, ConfigurableFieldMultiOption],
     description: Optional[str],
 ) -> ConfigurableFieldSpec:
-    enum = StrEnum(  # type: ignore[call-overload]
-        spec.name or spec.id,
-        ((v, v) for v in list(spec.options.keys())),
-    )
+    if enum := _enums_for_spec.get(spec):
+        pass
+    else:
+        enum = StrEnum(  # type: ignore[call-overload]
+            spec.name or spec.id,
+            ((v, v) for v in list(spec.options.keys())),
+        )
+        _enums_for_spec[spec] = cast(Type[StrEnum], enum)
     if isinstance(spec, ConfigurableFieldSingleOption):
         return ConfigurableFieldSpec(
             id=spec.id,

libs/langchain/langchain/schema/runnable/utils.py

@@ -250,6 +250,9 @@ class ConfigurableField(NamedTuple):
     description: Optional[str] = None
     annotation: Optional[Any] = None
 
+    def __hash__(self) -> int:
+        return hash((self.id, self.annotation))
+
 
 class ConfigurableFieldSingleOption(NamedTuple):
     """A field that can be configured by the user with a default value."""
@@ -261,6 +264,9 @@ class ConfigurableFieldSingleOption(NamedTuple):
     name: Optional[str] = None
     description: Optional[str] = None
 
+    def __hash__(self) -> int:
+        return hash((self.id, tuple(self.options.items()), self.default))
+
 
 class ConfigurableFieldMultiOption(NamedTuple):
     """A field that can be configured by the user with multiple default values."""
@@ -272,6 +278,9 @@ class ConfigurableFieldMultiOption(NamedTuple):
     name: Optional[str] = None
     description: Optional[str] = None
 
+    def __hash__(self) -> int:
+        return hash((self.id, tuple(self.options.items()), tuple(self.default)))
+
 
 AnyConfigurableField = Union[
     ConfigurableField, ConfigurableFieldSingleOption, ConfigurableFieldMultiOption

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

@@ -941,7 +941,8 @@ def test_configurable_fields_example() -> None:
         )
     )
 
-    chain_configurable = prompt | fake_llm
+    # deduplication of configurable fields
+    chain_configurable = prompt | fake_llm | (lambda x: {"name": x}) | prompt | fake_llm
 
     assert chain_configurable.invoke({"name": "John"}) == "a"