Fix regression when creating nested ConfigurableResource with pydantic >= v.2.5.0

python_modules/dagster/dagster/_config/pythonic_config/resource.py

@@ -834,7 +834,7 @@ def _is_annotated_as_resource_type(annotation: type, metadata: list[str]) -> boo
     """Determines if a field in a structured config class is annotated as a resource type or not."""
     from dagster._config.pythonic_config.type_check_utils import safe_is_subclass
 
-    if metadata and metadata[0] == "resource_dependency":
+    if metadata and any(m == "resource_dependency" for m in metadata):
         return True
 
     if is_closed_python_optional_type(annotation):

python_modules/dagster/dagster/_config/pythonic_config/typing_utils.py

@@ -105,6 +105,8 @@ class FooResource(ConfigurableResource):
     """
 
     def __new__(cls, name, bases, namespaces, **kwargs) -> Any:
+        from pydantic.fields import FieldInfo
+
         # Gather all type annotations from the class and its base classes
         annotations = namespaces.get("__annotations__", {})
         for field in annotations:
@@ -128,11 +130,20 @@ def __new__(cls, name, bases, namespaces, **kwargs) -> Any:
                     base = annotations[field]
                     annotations[field] = Annotated[
                         Union[
-                            LateBoundTypesForResourceTypeChecking.get_partial_resource_type(base),
                             base,
+                            LateBoundTypesForResourceTypeChecking.get_partial_resource_type(base),
                         ],
                         "resource_dependency",
                     ]
+                    # Pydantic 2.5.0 changed the default union mode to "smart", which causes
+                    # partial resource initialization to fail, since Pydantic would attempt to
+                    # initialize a PartialResource with parameters which are invalid.
+                    # https://github.com/pydantic/pydantic-core/pull/867
+                    # Here, we explicitly set the union mode to "left_to_right".
+                    # https://docs.pydantic.dev/latest/concepts/unions/#left-to-right-mode
+                    namespaces[field] = FieldInfo(
+                        union_mode="left_to_right", annotation=annotations[field]
+                    )
 
         namespaces["__annotations__"] = annotations
         return super().__new__(cls, name, bases, namespaces, **kwargs)

python_modules/dagster/dagster_tests/core_tests/resource_tests/pythonic_resources/test_nesting.py

@@ -1030,3 +1030,25 @@ def my_asset(db: TopLevelResource):
         .success
     )
     assert completed["yes"]
+
+
+def test_nested_resources_direct_config_fully_populated() -> None:
+    """Covers regression introduced in pydantic v2.5.0 where union validation changed to Smart
+    and direct initialization of nested ConfigurableResources stopped working.
+    """
+    import pydantic
+
+    class Inner(ConfigurableResource):
+        b: str
+
+    class Outer(ConfigurableResource):
+        a: str = pydantic.Field(default="a")
+        inner: Inner
+
+    # model_validate() on NESTED ConfigurableResource worked with pydantic v2.4.2, but stopped working on v2.5.0.
+    result = Outer.model_validate(dict(a="a", inner=dict(b="b")))
+    # >> TypeError: PartialResource.__init__() got an unexpected keyword argument 'b'
+    assert isinstance(result, Outer)
+    assert result.a == "a"
+    assert isinstance(result.inner, Inner)
+    assert result.inner.b == "b"