Macro otter_nodejs_tests::serde_with_compat

macro_rules! serde_with_compat {
    {
  [ $( #[ $($attrs:meta)* ] )* ] [ $vis:vis ] [ $($intro:tt)* ]
    $main:ident=$main_s:literal $new:ident $compat_s:literal
  [ $($body:tt)* ]
} => { ... };
}

Allows the use of serde for a compat struct

Ideally we would have

#[derive(Deserialize)]
#[serde(try_from=Compat)]
struct Main { /* new definition */ }

#[derive(Deserialize)]
#[serde(untagged)]
enum Compat { V1(Main), V2(Old) }

#[derive(Deserialize)]
struct Old { /* old version we still want to read */ }

impl TryFrom<Compat> for Main { /* ... */ }

But the impl for Compat ends up honouring the try_from on Main so is recursive. We solve that abusing serde’s remote feature.

For an example, see IOccultIlk.

The name of the main structure must be passed twice, once as an identifier and once as a literal, because stringify! doesn’t work in the serde attribute.