lighthouse/testing/ef_tests
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
..
src Implement SSZ union type (#2579) 2021-09-25 05:58:36 +00:00
tests Update spec tests to v1.1.0-beta.4 (#2548) 2021-09-25 05:58:35 +00:00
.gitignore Update spec tests to v1.1.0-beta.4 (#2548) 2021-09-25 05:58:35 +00:00
Cargo.toml Implement SSZ union type (#2579) 2021-09-25 05:58:36 +00:00
check_all_files_accessed.py Update spec tests to v1.1.0-beta.4 (#2548) 2021-09-25 05:58:35 +00:00
Makefile Update spec tests to v1.1.0-beta.4 (#2548) 2021-09-25 05:58:35 +00:00
README.md Update spec tests to v1.1.0-beta.4 (#2548) 2021-09-25 05:58:35 +00:00

Consensus Specification Tests

This crate parses and executes the test vectors at ethereum/consensus-spec-tests.

Functionality is achieved only via the $ cargo test --features ef_tests command.

Running the Tests

Because the test vectors are very large, we do not download or run them by default. To download them, run (in this directory):

$ make

Note: this may download hundreds of MB of compressed archives from the ethereum/consensus-spec-tests, which may expand into several GB of files.

If successful, you should now have the extracted tests in ./consensus-spec-tests.

Run them with:

$ cargo test --features ef_tests

The tests won't run without the ef_tests feature enabled (this is to ensure that a top-level cargo test --all won't fail on missing files).

Saving Space

When you download the tests, the downloaded archives will be kept in addition to the extracted files. You have several options for saving space:

  1. Delete the archives (make clean-archives), and keep the extracted files. Suitable for everyday use, just don't re-run make or it will redownload the archives.
  2. Delete the extracted files (make clean-test-files), and keep the archives. Suitable for CI, or temporarily saving space. If you re-run make it will extract the archives rather than redownloading them.
  3. Delete everything (make clean). Good for updating to a new version, or if you no longer wish to run the EF tests.