Bug: SerializationException on partial DTO for nested Pydantic model with custom type

[gsakkis]

Bug: SerializationException on partial DTO for nested Pydantic model with custom type

[provinzkraut]

This is a bug but not exactly the one reported here :)

The difference between the partial and non-partial is expected; In one case the missing field is caught early by the DTO because it is defined there as required. In the other case where all fields can potentially be missing, Pydantic is reporting the exception, so you're getting an error message from Pydantic as well. Since the Pydantic error message includes, by default, a reference to the object in question, this is also included in the error response, which Litestar is trying to serlialise here. Since you are using a custom type but are not telling Litestar about how to serialise it, the exception is thrown. You'd need to add e.g. type_encoders={PydanticCustomID: lambda c: c.value} to your app for this to work properly.

That being said, there's also a bug where we don't use the type_encoders properly inside a plain text exception response. I'm cooking up a PR for this at the moment.

[github-actions]

This issue has been closed in #3284. The change will be included in the upcoming patch release.

[github-actions]

A fix for this issue has been released in v2.8.0