feat: add comprehensive bb_rs compatibility tests for barretenberg-rs

[johnathan79717]

Summary

• Add FFI backend tests ported from zkpassport/aztec-packages bb_rs tests
• 56 FFI tests covering AES, Blake2s, BN254, ECDSA, Grumpkin, Pedersen, Poseidon, Schnorr, and secp256k1
• Fixed TypeScript code generator (rust_codegen.ts) to properly serialize [Vec<u8>; 4] types used by Poseidon2Permutation state

Original bb_rs tests for comparison: https://github.com/zkpassport/aztec-packages/tree/pr/obsidion-mobile-devnet/barretenberg/bb_rs/src/barretenberg_api/tests

Changes

TypeScript Code Generator (barretenberg/ts/src/cbind/rust_codegen.ts)

• Added needsSerdeArray4Bytes() method to detect [Vec<u8>; 4] field types
• Added serde_array4_bytes helper module to generated_types.rs for proper msgpack serialization of fixed-size byte array tuples
• This fixes the poseidon2_permutation API which uses 4-element state arrays

FFI Tests (barretenberg/rust/tests/src/ffi/)

• aes.rs, blake2s.rs, bn254.rs, ecdsa.rs, grumpkin.rs, pedersen.rs, poseidon.rs, schnorr.rs, secp256k1.rs
• Require --features ffi and linker flags:

  RUSTFLAGS="-C link-arg=-Wl,--allow-multiple-definition" cargo test --features ffi

Not Ported

The ACIR tests from the Obsidion bb_rs (acir.rs) were not ported because:

1. The Obsidion bb_rs uses direct FFI bindings (acir::get_circuit_sizes, acir::acir_vk_as_fields_mega_honk), while barretenberg-rs uses a pipe-based msgpack protocol with different method signatures
2. The JSON fixture files referenced by include_str!() (vk_in_args.json, vk_serialized.json) don't exist in the Obsidion repository
3. The equivalent functionality exists in barretenberg-rs (circuit_stats, mega_vk_as_fields) but requires structured CircuitInput types rather than raw bytes

Test plan

• All 56 FFI tests pass locally with RUSTFLAGS
• CI passes

[ludamad]

Looking good :) and yeah the goal is to show a proof of concept of bb-rs being fully moved over, and adapt their tests to the new format at that time (tho not strictly necessary for those redundant here, but some sanity checks are good)

[johnathan79717]

Looking good :) and yeah the goal is to show a proof of concept of bb-rs being fully moved over, and adapt their tests to the new format at that time (tho not strictly necessary for those redundant here, but some sanity checks are good)

I thought if we can port their tests, it already shows that our FfiBackend can replace bb-rs? Or is a wrapper that resembles the original bb-rs preferrable?

[johnathan79717]

For reviewers: The original bb_rs tests from Obsidion can be found at https://github.com/zkpassport/aztec-packages/tree/pr/obsidion-mobile-devnet/barretenberg/bb_rs/src/barretenberg_api/tests for comparison.