lighthouse/consensus/state_processing/Cargo.toml
Paul Hauner fe52322088 Implement SSZ union type (#2579)
## Issue Addressed

NA

## Proposed Changes

Implements the "union" type from the SSZ spec for `ssz`, `ssz_derive`, `tree_hash` and `tree_hash_derive` so it may be derived for `enums`:

https://github.com/ethereum/consensus-specs/blob/v1.1.0-beta.3/ssz/simple-serialize.md#union

The union type is required for the merge, since the `Transaction` type is defined as a single-variant union `Union[OpaqueTransaction]`.

### Crate Updates

This PR will (hopefully) cause CI to publish new versions for the following crates:

- `eth2_ssz_derive`: `0.2.1` -> `0.3.0`
- `eth2_ssz`: `0.3.0` -> `0.4.0`
- `eth2_ssz_types`: `0.2.0` -> `0.2.1`
- `tree_hash`: `0.3.0` -> `0.4.0`
- `tree_hash_derive`: `0.3.0` -> `0.4.0`

These these crates depend on each other, I've had to add a workspace-level `[patch]` for these crates. A follow-up PR will need to remove this patch, ones the new versions are published.

### Union Behaviors

We already had SSZ `Encode` and `TreeHash` derive for enums, however it just did a "transparent" pass-through of the inner value. Since the "union" decoding from the spec is in conflict with the transparent method, I've required that all `enum` have exactly one of the following enum-level attributes:

#### SSZ

-  `#[ssz(enum_behaviour = "union")]`
    - matches the spec used for the merge
-  `#[ssz(enum_behaviour = "transparent")]`
    - maintains existing functionality
    - not supported for `Decode` (never was)
    
#### TreeHash

-  `#[tree_hash(enum_behaviour = "union")]`
    - matches the spec used for the merge
-  `#[tree_hash(enum_behaviour = "transparent")]`
    - maintains existing functionality

This means that we can maintain the existing transparent behaviour, but all existing users will get a compile-time error until they explicitly opt-in to being transparent.

### Legacy Option Encoding

Before this PR, we already had a union-esque encoding for `Option<T>`. However, this was with the *old* SSZ spec where the union selector was 4 bytes. During merge specification, the spec was changed to use 1 byte for the selector.

Whilst the 4-byte `Option` encoding was never used in the spec, we used it in our database. Writing a migrate script for all occurrences of `Option` in the database would be painful, especially since it's used in the `CommitteeCache`. To avoid the migrate script, I added a serde-esque `#[ssz(with = "module")]` field-level attribute to `ssz_derive` so that we can opt into the 4-byte encoding on a field-by-field basis.

The `ssz::legacy::four_byte_impl!` macro allows a one-liner to define the module required for the `#[ssz(with = "module")]` for some `Option<T> where T: Encode + Decode`.

Notably, **I have removed `Encode` and `Decode` impls for `Option`**. I've done this to force a break on downstream users. Like I mentioned, `Option` isn't used in the spec so I don't think it'll be *that* annoying. I think it's nicer than quietly having two different union implementations or quietly breaking the existing `Option` impl.

### Crate Publish Ordering

I've modified the order in which CI publishes crates to ensure that we don't publish a crate without ensuring we already published a crate that it depends upon.

## TODO

- [ ] Queue a follow-up `[patch]`-removing PR.
2021-09-25 05:58:36 +00:00

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TOML

[package]
name = "state_processing"
version = "0.2.0"
authors = ["Paul Hauner <paul@paulhauner.com>", "Michael Sproul <michael@sigmaprime.io>"]
edition = "2018"
[dev-dependencies]
env_logger = "0.9.0"
serde = "1.0.116"
serde_derive = "1.0.116"
lazy_static = "1.4.0"
serde_yaml = "0.8.13"
beacon_chain = { path = "../../beacon_node/beacon_chain" }
[dependencies]
bls = { path = "../../crypto/bls" }
integer-sqrt = "0.1.5"
itertools = "0.10.0"
eth2_ssz = "0.4.0"
eth2_ssz_types = "0.2.1"
merkle_proof = { path = "../merkle_proof" }
log = "0.4.11"
safe_arith = { path = "../safe_arith" }
tree_hash = "0.4.0"
tree_hash_derive = "0.4.0"
types = { path = "../types", default-features = false }
rayon = "1.4.1"
eth2_hashing = "0.2.0"
int_to_bytes = { path = "../int_to_bytes" }
smallvec = "1.6.1"
arbitrary = { version = "0.4.6", features = ["derive"], optional = true }
lighthouse_metrics = { path = "../../common/lighthouse_metrics", optional = true }
lazy_static = { version = "1.4.0", optional = true }
[features]
default = ["legacy-arith", "metrics"]
fake_crypto = ["bls/fake_crypto"]
legacy-arith = ["types/legacy-arith"]
metrics = ["lighthouse_metrics", "lazy_static"]
arbitrary-fuzz = [
"arbitrary",
"types/arbitrary-fuzz",
"bls/arbitrary",
"merkle_proof/arbitrary",
"eth2_ssz/arbitrary",
"eth2_ssz_types/arbitrary",
"tree_hash/arbitrary",
]