Documentation

Summary of the hard fork state

NOTE: HasHardForkHistory is the only abstraction that the consensus layer is aware in relation to potential hard forks, and is needed only for time translations (in block production and in the chain DB). It is independent from the hard fork combinator and can be used for blocks that never fork (in which case the Summary will be trivial) or indeed for blocks that do support transitions but do not use the hard fork combinator.

It is however useful to consider what this function means in the (typical) case that the hard fork combinator is used. The HFC introduces the concept of a partial ledger config, which is essentially the ledger config minus an EpochInfo. Whenever the HFC calls functions on the underlying ledger, it maintains enough state to be able to construct an EpochInfo on the fly and then combines that with the PartialLedgerConfig to get the full LedgerConfig. The config of the HFC itself however does not require an EpochInfo, and so the config that we pass here will not contain that EpochInfo (if it did, that would be strange: we'd be computing the Summary required to construct an EpochInfo while we already have one). Critically, the HFC implements hardForkSummary directly and does not call hardForkSummary in the underlying ledgers.

When running ledgers that are normally run using the HFC as standalone ledgers, then the LedgerConfig here must indeed already contain timing information, and so this function becomes little more than a projection (indeed, in this case the LedgerState should be irrelevant).