In #33 I had to have the triplet bellpepper, bellpepper-core and arecibo as dependencies, and I got a bit lost in how they are managed.

Looking at a some projects having those as dependency, it seems that most of them have adopted the "fork" approach that let's us quickly pull updates (lurk-rs, circom-scotia, arecibo, ...) while others (such as this one) have opted for a fixed crate version.

I think we would probably gain to try and unify the way we import those dependencies.

As @huitseeker suggested I tried various triplets of dependencies and it seems that the one that worked for me is bellpepper = 0.4.1 bellpepper-core as fork and arecibo as fork. We could use this as a global approach.

There might be an issue with the field emulation library. The tests associated with bls12-381 emulation with pasta fields pass. However, when I changed the field from bls12-381's base field to BN254's base field (and adjusted EmulatedFieldParams trait appropriately), the tests fail in the following manner (similar errors for other tests).

---- fields::bn_fp::tests::test_random_add stdout ----
fail: "a+b = c/a = b/check limbs equality/right shift to get carry 0/enforce equality between input value and weighted sum of higher order bits"
Some("a+b = c/a = b/check limbs equality/right shift to get carry 0/enforce equality between input value and weighted sum of higher order bits")
fail: "a+b = c/a = b/check limbs equality/right shift to get carry 0/enforce equality between input value and weighted sum of higher order bits"
thread 'fields::bn_fp::tests::test_random_add' panicked at crates/bls12381/src/fields/bn_fp.rs:279:9:
assertion failed: cs.is_satisfied()
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Here's what the trait implementation looks like:

use halo2curves::bn256::Fq as BnFp;

pub struct Bn254FpParams;

impl EmulatedFieldParams for Bn254FpParams {
    fn num_limbs() -> usize {
        4
    }

    fn bits_per_limb() -> usize {
        64
    }

    fn modulus() -> BigInt {
        BigInt::parse_bytes(
            b"30644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd47",             
            16,
        )
        .unwrap()
    }

    fn is_modulus_pseudo_mersenne() -> bool {
        false
    }

    fn pseudo_mersenne_params() -> Option<PseudoMersennePrime> {
        None
    }
}

pub type Bn254Fp<F> = EmulatedFieldElement<F, Bn254FpParams>;

actions-rs is obsolete for our toolchain and should be phased out

We have tests for constraint counts in Nova:
https://github.com/lurk-lab/arecibo/blob/605f89990666cae63ff534245ea701199fe0df82/src/circuit.rs#L462-L502
https://github.com/lurk-lab/arecibo/blob/605f89990666cae63ff534245ea701199fe0df82/src/supernova/circuit.rs#L836
https://github.com/lurk-lab/arecibo/blob/605f89990666cae63ff534245ea701199fe0df82/src/supernova/test.rs#L568

And Lurk:
https://github.com/lurk-lab/lurk-rs/blob/f9f87545a3ffa0cf921fa2557021a7b9040b7ad5/src/lem/eval.rs#L1732

and in Lurk for MemoSet:
https://github.com/lurk-lab/lurk-rs/blob/f9f87545a3ffa0cf921fa2557021a7b9040b7ad5/src/coprocessor/memoset/mod.rs#L791

That count the number of expected constraints in a circuit. We should add one for the recently added keccak/sha3 gadgets (see #14) ideally using expect_test

As said in lurk-lab/arecibo#347, we have in arecibo a few gadget utilities that have been written. So far, they are only available to this arecibo crate. While working in bellpepper-gadgets or any other gadget repositories, a few of those utilities could come in handy.

There are already cases where they have been copied so I believe that migrating them will prove useful.

The bls12_381 crate does not export some internal items that are used in the bellpepper-bls12381 gadget. Currently this fork lives (temporarily) at wrinqle/bls12_381

We should get rid of this git dependency, doing one of:

• Make a "proper" fork that exposes the necessary items and publish it on crates.io/put it under the lurk-lab github organization
• Replace the bls12_381 native dependency with something like blst (or anything else that exposes enough internals) instead (this would be a non-trivial change: we make use of many internal functions for some tests)

This repo lacks our CoC:
https://github.com/lurk-lab/lurk-rs/blob/master/CODE_OF_CONDUCT.md

And our dependabot config:
https://github.com/lurk-lab/lurk-rs/blob/master/.github/dependabot.yml

Some dependencies specified in Cargo.toml are not needed.

Check the unused dependencies sanity check workflow for details.

This issue was raised by the workflow at https://github.com/lurk-lab/ci-workflows/tree/main/.github/workflows/unused-deps.yml.

Note
If this is a false positive, please refer to the cargo-udeps docs on how to ignore the dependencies.

The conditionally_select method of EmulatedFieldElement unwraps the boolean condition which is None when running with TestCS. This happens at

The fix involves replacing unwrap with unwarp_or_default

Similar to what we have for the rest of our infrastructure.