Fix: checkpointing/epoch growth bug

x/checkpointing/abci.go

@@ -25,10 +25,10 @@ func BeginBlocker(ctx sdk.Context, k keeper.Keeper, req abci.RequestBeginBlock)
  // if this block is the second block of an epoch
  epoch := k.GetEpoch(ctx)
  if epoch.IsSecondBlock(ctx) {
- // note that this epochNum is obtained before the BeginBlocker of the epoching module is executed
- // meaning that the epochNum has not been incremented upon a new epoch
+ // note that this epochNum is obtained after the BeginBlocker of the epoching module is executed
+ // meaning that the epochNum has been incremented upon a new epoch
  lch := ctx.BlockHeader().LastCommitHash
- err := k.BuildRawCheckpoint(ctx, epoch.EpochNumber, lch)
+ err := k.BuildRawCheckpoint(ctx, epoch.EpochNumber-1, lch)
  if err != nil {
  panic("failed to generate a raw checkpoint")
  }

x/epoching/types/epoching.go

@@ -14,7 +14,7 @@ func (e Epoch) GetLastBlockHeight() uint64 {
 
 func (e Epoch) GetSecondBlockHeight() uint64 {
  if e.EpochNumber == 0 {
- return 0
+ panic("should not be called when epoch number is zero")
  }
  return e.FirstBlockHeight + 1
 }