attempt fix for generation

libs/core/langchain_core/load/serializable.py

@@ -209,18 +209,15 @@ class Serializable(BaseModel, ABC):
         if not self.is_lc_serializable():
             return self.to_json_not_implemented()
 
-        model_fields = type(self).model_fields
+        fields = {**self.__class__.model_fields, **self.__class__.model_computed_fields}
         secrets = {}
         # Get latest values for kwargs if there is an attribute with same name
         lc_kwargs = {}
-        for k, v in self:
-            if not _is_field_useful(self, k, v):
-                continue
-            # Do nothing if the field is excluded
-            if k in model_fields and model_fields[k].exclude:
+        for k, v in self.model_dump().items():
+            if not _is_field_useful(self.__class__, k, v):
                 continue
 
-            lc_kwargs[k] = getattr(self, k, v)
+            lc_kwargs[k] = v
 
         # Merge the lc_secrets and lc_attributes from every class in the MRO
         for cls in [None, *self.__class__.mro()]:
@@ -253,9 +250,7 @@ class Serializable(BaseModel, ABC):
             # that are not present in the fields.
             for key in list(secrets):
                 value = secrets[key]
-                if (key in model_fields) and (
-                    alias := model_fields[key].alias
-                ) is not None:
+                if (key in fields) and (alias := fields[key].alias) is not None:
                     secrets[alias] = value
             lc_kwargs.update(this.lc_attributes)
 
@@ -280,11 +275,11 @@ class Serializable(BaseModel, ABC):
         return to_json_not_implemented(self)
 
 
-def _is_field_useful(inst: Serializable, key: str, value: Any) -> bool:
+def _is_field_useful(class_: type[Serializable], key: str, value: Any) -> bool:
     """Check if a field is useful as a constructor argument.
 
     Args:
-        inst: The instance.
+        class_: The class.
         key: The key.
         value: The value.
 
@@ -294,8 +289,10 @@ def _is_field_useful(inst: Serializable, key: str, value: Any) -> bool:
         If the field is not required and the value is None, it is useful if the
         default value is different from the value.
     """
-    field = type(inst).model_fields.get(key)
-    if not field:
+    if class_.model_computed_fields.get(key):
+        return True
+
+    if not (field := class_.model_fields.get(key)):
         return False
 
     if field.is_required():

libs/core/tests/unit_tests/load/test_serializable.py

@@ -1,4 +1,4 @@
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, computed_field
 
 from langchain_core.load import Serializable, dumpd, load
 from langchain_core.load.serializable import _is_field_useful
@@ -114,12 +114,26 @@ def test__is_field_useful() -> None:
         )
 
     foo = Foo(x=ArrayObj(), y=NonBoolObj(), z=ArrayObj())
-    assert _is_field_useful(foo, "x", foo.x)
-    assert _is_field_useful(foo, "y", foo.y)
+    assert _is_field_useful(Foo, "x", foo.x)
+    assert _is_field_useful(Foo, "y", foo.y)
 
     foo = Foo(x=default_x, y=default_y, z=ArrayObj())
-    assert not _is_field_useful(foo, "x", foo.x)
-    assert not _is_field_useful(foo, "y", foo.y)
+    assert not _is_field_useful(Foo, "x", foo.x)
+    assert not _is_field_useful(Foo, "y", foo.y)
+
+    class Bar(Serializable):
+        x: int
+        y: int
+
+        @computed_field
+        @property
+        def z(self) -> int:
+            return self.x + self.y
+
+    bar = Bar(x=1, y=2)
+    assert _is_field_useful(Bar, "x", bar.x)
+    assert _is_field_useful(Bar, "y", bar.y)
+    assert _is_field_useful(Bar, "z", bar.z)
 
 
 class Foo(Serializable):