Accounts + Program IDL/Schema traits

[armaniferrante]

Motivation

Suppose I had a field foo of type crate_a::MyAccountsA that is embedded into crate_b::MyAccountsB as follows.

// crate_a/src/lib.rs

#[derive(Accounts)]
pub struct MyAccountsA {
 ...
}

// crate_b/src/lib.rs

#[derive(Accounts)]
pub struct MyAccountsB {
  foo: crate_a::MyAccountsA,
}

I would want the IDL emitted for crate_b to have all the type i+ account nformation for foo.

Currently this information is only available to crate_a, and so crate_b would either have to re-define crate_a::MyAccountsA in its own src/lib.rs or use all the accounts in flattened form, instead of composing crate_a::MyAccountsA directly.

Solution

To achieve this, we can have the various macros generate trait implementations providing IDL/type information. Additionally, we probably need to add some type of build.rs file that calls these generated traits to output the IDL, instead of just parsing the program's file directly, as we do now.

The build steps might be organized into

1. Walk entire crate to find IDL types.
2. Generate idl.rs file, invoking the traits on the IDL types.
3. Emit IDL by running the build.rs file

[paul-schaaf]

related: #454