Generation to trait-based collection (Codama integration)

[nutafrost]

The current IDL generation relies on parsing source code paths, which is fragile. We should move toward a systematic approach using traits that Codama can leverage.

Requirements:

• Define a ToIDL trait for custom types to describe their own schema.
• Implement a traversal system where the program entry point calls instruction traits, which in turn call account traits to build the full IDL.
• Ensure support for Codama "plugins" to handle complex encoding (e.g., bit-packing/offsetting in zero-copy structs) so that the generated TypeScript/Go clients remain user-friendly.

[nutafrost]

Resolved in V2

[acheroncrypto]

I've just seen this being completed in v2, and I haven't checked the implementation, but wanted to share some thoughts and make certain clarifications on this issue.

The current IDL generation relies on parsing source code paths, which is fragile.

This is only partially correct; the majority of the IDL generation uses building (the feature is literally called idl-build and idl-parse was removed), and some parsing is done because of things like:

• Generics
• External non-Anchor types

It allows complex types like:

https://github.com/solana-foundation/anchor/blob/a51158d5e19a588df11e8875325f70fbca372465/tests/idl/programs/idl/src/lib.rs#L435-L449

• Define a ToIDL trait for custom types to describe their own schema.

This trait already exist (although with a different name) since v0.30:

https://github.com/solana-foundation/anchor/blob/a51158d5e19a588df11e8875325f70fbca372465/idl/src/build.rs#L14-L24

It can be used to completely define custom types. You can even implement it for external non-Anchor types like in this example:

https://github.com/solana-foundation/anchor/blob/a51158d5e19a588df11e8875325f70fbca372465/tests/idl/programs/idl/src/lib.rs#L490

https://github.com/solana-foundation/anchor/blob/a51158d5e19a588df11e8875325f70fbca372465/tests/idl/programs/idl/src/lib.rs#L515-L534

• Implement a traversal system where the program entry point calls instruction traits, which in turn call account traits to build the full IDL.

This is literally what the current IDL generation since v0.30 does. I believe Anchor was the first to do something like this, at least on the Solana ecosystem.

• Ensure support for Codama "plugins"

This is the only thing that was missing.

[jamie-osec]

Reopening given that Codama is not supported yet