feat(nodes): validate default values for all fields

This prevents issues where the node is defined with an invalid default value, which would guarantee an error during a ser/de roundtrip.

- Upstream issue requesting this functionality be built-in to pydantic: pydantic/pydantic#8722
- Upstream PR that implements the functionality: pydantic/pydantic-core#1593

Author: psychedelicious

invokeai/app/invocations/baseinvocation.py

@@ -477,6 +477,31 @@ def validate_fields(model_fields: dict[str, FieldInfo], model_type: str) -> None
     return None
 
 
+class NoDefaultSentinel:
+    pass
+
+
+def validate_field_default(field_name: str, invocation_type: str, annotation: Any, field_info: FieldInfo) -> None:
+    """Validates the default value of a field against its pydantic field definition."""
+
+    assert isinstance(field_info.json_schema_extra, dict), "json_schema_extra is not a dict"
+
+    # By the time we are doing this, we've already done some pydantic magic by overriding the original default value.
+    # We store the original default value in the json_schema_extra dict, so we can validate it here.
+    orig_default = field_info.json_schema_extra.get("orig_default", NoDefaultSentinel)
+
+    if orig_default is NoDefaultSentinel:
+        return
+
+    TempDefaultValidator = create_model("TempDefaultValidator", field_to_validate=(annotation, field_info))
+
+    # Validate the default value against the annotation
+    try:
+        TempDefaultValidator(field_to_validate=orig_default)
+    except Exception as e:
+        raise ValueError(f"Default value for field {field_name} on invocation {invocation_type} is invalid, {e}") from e
+
+
 def is_optional(annotation: Any) -> bool:
     """
     Checks if the given annotation is optional (i.e. Optional[X], Union[X, None] or X | None).
@@ -529,8 +554,12 @@ def wrapper(cls: Type[TBaseInvocation]) -> Type[TBaseInvocation]:
             assert isinstance(field_info.json_schema_extra, dict), (
                 f"{field_name} on invocation {invocation_type} has a non-dict json_schema_extra, did you forget to use InputField?"
             )
+
+            validate_field_default(field_name, invocation_type, annotation, field_info)
+
             if field_info.default is None and not is_optional(annotation):
                 annotation = annotation | None
+
             fields[field_name] = (annotation, field_info)
 
         # Add OpenAPI schema extras