More comments, update sim for NextValSet

PENDING.md

@@ -28,10 +28,9 @@ BREAKING CHANGES
     * [x/stake, x/slashing] [#1305](https://github.com/cosmos/cosmos-sdk/issues/1305) - Rename "revoked" to "jailed"
     * [x/stake] [#1676] Revoked and jailed validators put into the unbonding state
     * [x/stake] [#1877] Redelegations/unbonding-delegation from unbonding validator have reduced time
-    * [x/stake] \#2040 Validator operator type has now changed to `sdk.ValAddress`
-      * A new bech32 prefix has been introduced for Tendermint signing keys and
-        addresses, `cosmosconspub` and `cosmoscons` respectively.
     * [x/slashing] \#1789 Slashing changes for Tendermint validator set offset (NextValSet)
+    * [x/stake] [\#2040](https://github.com/cosmos/cosmos-sdk/issues/2040) Validator
+    operator type has now changed to `sdk.ValAddress`
     * [x/stake] [\#2221](https://github.com/cosmos/cosmos-sdk/issues/2221) New
     Bech32 prefixes have been introduced for a validator's consensus address and
     public key: `cosmosvalcons` and `cosmosvalconspub` respectively. Also, existing Bech32 prefixes have been

x/mock/simulation/random_simulate_blocks.go

@@ -77,6 +77,9 @@ func SimulateFromSeed(tb testing.TB, app *baseapp.BaseApp,
 	}
 
 	validators := initChain(r, accs, setups, app, appStateFn)
+	// Second variable to keep pending validator set (delayed one block since TM 0.24)
+	// Initially this is the same as the initial validator set
+	nextValidators := validators
 
 	header := abci.Header{Height: 0, Time: timestamp}
 	opCount := 0
@@ -160,8 +163,9 @@ func SimulateFromSeed(tb testing.TB, app *baseapp.BaseApp,
 		// Generate a random RequestBeginBlock with the current validator set for the next block
 		request = RandomRequestBeginBlock(r, validators, livenessTransitionMatrix, evidenceFraction, pastTimes, pastVoteInfos, event, header)
 
-		// Update the validator set
+		// Update the validator set, which will be reflected in the application on the next block
-		validators = updateValidators(tb, r, validators, res.ValidatorUpdates, event)
+		validators = nextValidators
+		nextValidators = updateValidators(tb, r, validators, res.ValidatorUpdates, event)
 	}
 	if stopEarly {
 		DisplayEvents(events)

x/slashing/keeper.go

@@ -63,6 +63,9 @@ func (k Keeper) handleDoubleSign(ctx sdk.Context, addr crypto.Address, infractio
 	logger.Info(fmt.Sprintf("Fraction slashed capped by slashing period from %v to %v", fraction, revisedFraction))
 
 	// We need to retrieve the stake distribution which signed the block, so we subtract ValidatorUpdateDelay from the evidence height.
+	// Note that this *can* result in a "distributionHeight" of -1,
+	// i.e. at the end of the pre-genesis block (none) = at the beginning of the genesis block.
+	// That's fine since this is just used to filter unbonding delegations & redelegations.
 	distributionHeight := infractionHeight - ValidatorUpdateDelay
 
 	// Slash validator
@@ -128,6 +131,9 @@ func (k Keeper) handleValidatorSignature(ctx sdk.Context, addr crypto.Address, p
 				pubkey.Address(), minHeight, k.MinSignedPerWindow(ctx)))
 			// We need to retrieve the stake distribution which signed the block, so we subtract ValidatorUpdateDelay from the evidence height,
 			// and subtract an additional 1 since this is the LastCommit.
+			// Note that this *can* result in a "distributionHeight" of -1 or -2,
+			// i.e. at the end of the pre-genesis block (none) = at the beginning of the genesis block.
+			// That's fine since this is just used to filter unbonding delegations & redelegations.
 			distributionHeight := height - ValidatorUpdateDelay - 1
 			k.validatorSet.Slash(ctx, consAddr, distributionHeight, power, k.SlashFractionDowntime(ctx))
 			k.validatorSet.Jail(ctx, consAddr)