Non-ObjectId _id fields

[loafofpiecrust]

I recently started checking out this library but found a hurdle to my adoption: I want to use custom types in the _id field which serialize to a String. Would wither be able to support this, instead of strictly requiring id: Option<ObjectId>?

[aswinmurali-io]

If we have an option to use ObjectId as String like id: Option<String> that would be great!

This is my scenario. The prost crate supports converting .proto protobuf schemas to rust struct definitions. It will automatically convert protobuf schema types to rust types. The prost-build crate supports additional features to add custom derives in the generated rusts. I used it to derive the generated struct with serde::Serializable, serde::Deserizable & wither::Model. This way using the prost crate, from protobuf I get fully generated rust code that works directly with mongodb with the abstraction advantage of wither!! It's a dream come true when it comes to scalability & maintainability.

But there is one problem. Unlike all the basic std types I used in my protobuf schemas. The id attribute uses the wither::bson::oid::ObjectId type which does not implement the prost::Message trait need for deserializing protobuf data. Kinda makes sense because ObjectId is not a type that is supported by protobuf anyway. But the prost crate implemented String with the prost::Message trait since it's a basic type support in both rust and protobuf. Since ObjectId technically can be parsed from a String we should be able to make it work. But the wither::Model trait is forcing me to only use the exact Option<ObjectId>.

If there was a flag to support Option<String> it would finally bridge the gap between all the tech I use from

• protobuf - fast binary data exchange format with schema support
• prost - for generating rust struct from protobuf schema & deserializing them from protobuf data.
• serde - general serializing & deserializing
• mongo - my database of choice
• wither - makes mongodb easier for me

If there is a monkey-patch solution please do let me know. I can fork wither and do the change until there is an official merge.

cc @thedodd