Exposing consuming methods in `UserDataMethods`?

[ysimonson]

Is it possible to expose a method that consumes self in UserDataMethods? The motivation is that I want to expose the commit method of postgres connections, however the typical add_method/add_method_mut won't work.

[kyren]

That seems like a reasonable request, now that invalidation is an accepted and normal part of the API with ‘scope’.

However, the error message on access might not be great. I can still add the feature, but in some cases it might be preferable to have the Userdata wrap an Option and return a custom error, and you can of course do that in the meantime.

[ysimonson]

Wouldn't that have the same issue? e.g. assuming I wrap the Option<postgres::transaction::Transaction> in a newtype since it's defined outside of the crate, and the method definition looked something like this:

methods.add_method_mut("commit", |_, this, ()| {
    if let Some(trans) = this.0 {
        trans.commit().map_err(|err| LuaError::RuntimeError(format!("{}", err)))
    } else {
        Err(LuaError::RuntimeError("The transaction has already finished".to_string()))
    }
});

I'd still get a cannot move out of borrowed content error.

[kyren]

You can use Option::take

[ysimonson]

Oh man, TIL. Thanks @kyren! This works great as-is; I'll just close this out.