#[changeset_for] codegen issue

[mcasper]

Trying to use #[changeset_for] for the struct:

#[changeset_for(users)]
pub struct UserChanges {
    id: i32,
    first_name: Option<String>,
    last_name: Option<String>,
    email: Option<String>,
}

Produces the error:

src/main.rs:33:24: 33:24 error: the trait `diesel::query_source::Queriable<(diesel::types::Integer, diesel::types::VarChar, diesel::types::VarChar, diesel::types::VarChar)>` is not implemented for the type `UserChanges` [E0277]
src/main.rs:33 #[changeset_for(users)]
                                      ^
src/main.rs:33:1: 33:24 note: in this expansion of try! (defined in <std macros>)
src/main.rs:33:24: 33:24 help: run `rustc --explain E0277` to see a detailed explanation
error: aborting due to previous error

However, adding #[derive(Queriable)] to the struct annotation raises the error:

src/main.rs:34:24: 34:24 error: the trait `diesel::types::FromSqlRow<(diesel::types::Integer, diesel::types::VarChar, diesel::types::VarChar, diesel::types::VarChar)>` is not implemented for the type `(i32, core::option::Option<collections::string::String>, core::option::Option<collections::string::String>, core::option::Option<collections::string::String>)` [E0277]
src/main.rs:34 #[changeset_for(users)]
                                      ^
src/main.rs:34:1: 34:24 note: in this expansion of try! (defined in <std macros>)
src/main.rs:34:24: 34:24 help: run `rustc --explain E0277` to see a detailed explanation
error: aborting due to previous error

Halp

[sgrif]

You'll need to use two different structs for that use case. (Which makes sense if you think about it, you don't want to have to deal with options for reads, when you know the field is always present)

[sgrif]

(I might eventually be able to support reading a non-nullable field into an option, but at the moment coherence prevents it)

[mcasper]

I'm totally fine to (and prefer to) use separate structs for changesets and queriable, but the first error comes from just using #[changeset_for(users)] on the UserChanges struct

[sgrif]

Oh, whoops!

[sgrif]

^----- That commit probably also makes save_changes way more useful for your use case as well

[mcasper]

Definitely, that's awesome!