export_service! does not respect modules

[lastmjs]

When I run this code:

mod my_module {
    pub struct TestRecord {
        id: String,
    }

    #[ic_cdk_macros::update]
    fn test() -> TestRecord {
        TestRecord {
            id: "hello".to_string(),
        }
    }
}

I get these errors:

error[E0412]: cannot find type `TestRecord` in this scope
    --> src/src/lib.rs:3192:1
     |
3192 | candid::export_service!();
     | ^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
     |
     = note: this error originates in the macro `candid::export_service` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider importing this struct
     |
2    | use crate::my_module::TestRecord;
     |

This is a minimally reproducible example of an issue we're running into in Azle (TypeScript CDK). A simple one-off solution is to add a fully qualified path to TestRecord in the method return type, such as crate::my_module::TestRecord. This is difficult for us to do in a generalized fashion for Azle though.

It would be ideal if the export_service! macro could fully handle methods defined within their own modules inside of the main canister crate.

[chenyan-dfinity]

Is it possible to move the test function to the top-level? We are thinking of only allowing endpoint functions at the top level, or as an impl of a struct.

Defining endpoint functions in a module has security risks: when other people import this module, they suddenly get the same endpoint without notice. So while it's currently possible, it's not a recommended style.