Fix Bug On Startup Using Genesis.json

[nisdas]

This fixes a bug, when starting up and running the beacon-chain, by providing the initial validators from genesis.json as an argument to initialize state.

Due to validators not being initialized from genesis.json , it leads to there being no validators stored in the beacon state. After shuffling , ActiveValidatorIndices returns an empty slice, which leads there to being no committees so we get a divide by zero error. This PR will be fixing this issue.

[terencechain]

Thanks for fixing this! Just one comment on keeping InitialBeaconState generic and not pass genesis.json values as an extra argument. We should use initialValidatorDeposits instead.

[terencechain]

This is not part of the spec under get_initial_beacon_state . See https://github.com/ethereum/eth2.0-specs/blob/master/specs/core/0_beacon-chain.md#on-startup. I'd rather keep InitialBeaconState generic and not work with genesis.json which will be deprecated super soon, otherwise, it feels kinda hacky. Can we just pass the values of genesis.json (pub key and balances) inside initialValidatorDeposits and use that instead? It will still register via v.ProcessDeposit

[nisdas]

If we are going to deprecate genesis.json super soon, I rather do it in this PR then and have a clean break. Also i guess initialValidators is not used anywhere so I can start removing that too

[terencechain]

Exactly. So outside of InitialBeaconState, we should do something like:

If demo config:
Convert Genesis.json to initialValidatorDeposit

Lmk if that doesn't make sense

[terencechain]

Reason being genesisValidatorRegistry will always be empty when we don't use Genesis.json

[prestonvanloon]

What is the bug exactly?

[codecov]

Codecov Report

Merging #1258 into master will increase coverage by 2.89%.
The diff coverage is 79.59%.

@@            Coverage Diff             @@
##           master    #1258      +/-   ##
==========================================
+ Coverage   70.63%   73.52%   +2.89%     
==========================================
  Files          53       84      +31     
  Lines        4025     5809    +1784     
==========================================
+ Hits         2843     4271    +1428     
- Misses        959     1195     +236     
- Partials      223      343     +120

[terencechain]

looks good! thanks for the fix. One last thing, there's still a genesis-json reference under VALIDATOR_REGISTRATION.md, please remove that = )