lighthouse/consensus/tree_hash/tests/tests.rs

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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
use ssz_derive::Encode;
use tree_hash::{Hash256, MerkleHasher, TreeHash, BYTES_PER_CHUNK};
use tree_hash_derive::TreeHash;
#[derive(Encode)]
struct HashVec {
vec: Vec<u8>,
}
impl From<Vec<u8>> for HashVec {
fn from(vec: Vec<u8>) -> Self {
Self { vec }
}
}
impl tree_hash::TreeHash for HashVec {
fn tree_hash_type() -> tree_hash::TreeHashType {
tree_hash::TreeHashType::List
}
fn tree_hash_packed_encoding(&self) -> Vec<u8> {
unreachable!("List should never be packed.")
}
fn tree_hash_packing_factor() -> usize {
unreachable!("List should never be packed.")
}
fn tree_hash_root(&self) -> Hash256 {
let mut hasher =
MerkleHasher::with_leaves((self.vec.len() + BYTES_PER_CHUNK - 1) / BYTES_PER_CHUNK);
for item in &self.vec {
hasher.write(&item.tree_hash_packed_encoding()).unwrap()
}
let root = hasher.finish().unwrap();
tree_hash::mix_in_length(&root, self.vec.len())
}
}
fn mix_in_selector(a: Hash256, selector: u8) -> Hash256 {
let mut b = [0; 32];
b[0] = selector;
Hash256::from_slice(&eth2_hashing::hash32_concat(a.as_bytes(), &b))
}
fn u8_hash_concat(v1: u8, v2: u8) -> Hash256 {
let mut a = [0; 32];
let mut b = [0; 32];
a[0] = v1;
b[0] = v2;
Hash256::from_slice(&eth2_hashing::hash32_concat(&a, &b))
}
fn u8_hash(x: u8) -> Hash256 {
let mut a = [0; 32];
a[0] = x;
Hash256::from_slice(&a)
}
#[derive(TreeHash)]
#[tree_hash(enum_behaviour = "transparent")]
enum FixedTrans {
A(u8),
B(u8),
}
#[test]
fn fixed_trans() {
assert_eq!(FixedTrans::A(2).tree_hash_root(), u8_hash(2));
assert_eq!(FixedTrans::B(2).tree_hash_root(), u8_hash(2));
}
#[derive(TreeHash)]
#[tree_hash(enum_behaviour = "union")]
enum FixedUnion {
A(u8),
B(u8),
}
#[test]
fn fixed_union() {
assert_eq!(FixedUnion::A(2).tree_hash_root(), u8_hash_concat(2, 0));
assert_eq!(FixedUnion::B(2).tree_hash_root(), u8_hash_concat(2, 1));
}
#[derive(TreeHash)]
#[tree_hash(enum_behaviour = "transparent")]
enum VariableTrans {
A(HashVec),
B(HashVec),
}
#[test]
fn variable_trans() {
assert_eq!(
VariableTrans::A(HashVec::from(vec![2])).tree_hash_root(),
u8_hash_concat(2, 1)
);
assert_eq!(
VariableTrans::B(HashVec::from(vec![2])).tree_hash_root(),
u8_hash_concat(2, 1)
);
}
#[derive(TreeHash)]
#[tree_hash(enum_behaviour = "union")]
enum VariableUnion {
A(HashVec),
B(HashVec),
}
#[test]
fn variable_union() {
assert_eq!(
VariableUnion::A(HashVec::from(vec![2])).tree_hash_root(),
mix_in_selector(u8_hash_concat(2, 1), 0)
);
assert_eq!(
VariableUnion::B(HashVec::from(vec![2])).tree_hash_root(),
mix_in_selector(u8_hash_concat(2, 1), 1)
);
}