[explore] nested config with defaults

python_modules/dagster/dagster/_config/pythonic_config/config.py

@@ -414,6 +414,7 @@ def infer_schema_from_config_class(
 
     check.param_invariant(
         safe_is_subclass(model_cls, Config),
+        "model_cls",
         "Config type annotation must inherit from dagster.Config",
     )
 

python_modules/dagster/dagster/_config/pythonic_config/conversion_utils.py

@@ -101,12 +101,15 @@ def _convert_pydantic_field(
     if get_origin(pydantic_field.annotation) == Literal:
         return _convert_typing_literal_field(pydantic_field)
 
-    field_type = pydantic_field.annotation
+    field_type = (
+        pydantic_field.annotation
+    )  # here by just passing the field_type is where we lose any default values
     if safe_is_subclass(field_type, Config):
         inferred_field = infer_schema_from_config_class(
             field_type,
             description=pydantic_field.description,
         )
+        # but once we have the non-default inferred field, i'm not sure how we can then apply the defaults
         return inferred_field
     else:
         if not pydantic_field.is_required() and not is_closed_python_optional_type(field_type):

python_modules/dagster/dagster_tests/core_tests/pythonic_config_tests/test_pythonic_config_types.py

@@ -999,3 +999,41 @@ def echo_job():
     d = {"test": "test"}
     result = echo_job.execute_in_process(resources={"my_resource": ConfigWithAlias(alias_name=d)})
     assert result.output_for_node("echo_config") == d
+
+
+def test_nested_config_with_defaults() -> None:
+    class NestedConfig(Config):
+        a: str
+        b: int
+
+    class ConfigClassToConvert(Config):
+        nested: NestedConfig = Field(default=NestedConfig(a="a", b=1))
+        an_int: int = 2
+
+    fields = ConfigClassToConvert.to_fields_dict()
+
+    assert isinstance(fields, dict)
+    assert set(fields.keys()) == {
+        "nested",
+        "an_int",
+    }
+    assert fields["nested"].default_value == {"a": "a", "b": 1}
+    assert fields["an_int"].default_value == 2
+
+    class NestedConfigWithDefaults(Config):
+        a: str = "a"
+        b: int = 1
+
+    class ConfigClassToConvert(Config):
+        nested: NestedConfigWithDefaults
+        an_int: int = 2
+
+    fields = ConfigClassToConvert.to_fields_dict()
+
+    assert isinstance(fields, dict)
+    assert set(fields.keys()) == {
+        "nested",
+        "an_int",
+    }
+    assert fields["nested"].default_value == {"a": "a", "b": 1}
+    assert fields["an_int"].default_value == 2