try generic

x/lightclient/keeper/hook_listener.go

@@ -44,6 +44,11 @@ func (hook rollappHook) AfterUpdateState(
 		client, ok = hook.k.GetProspectiveCanonicalClient(ctx, rollappId, stateInfo.GetLatestHeight()-1)
 		if ok {
 			hook.k.SetCanonicalClient(ctx, rollappId, client)
+			// we now verified everything up to and including stateInfo.GetLatestHeight()-1
+			// so we should prune everything up to stateInfo.GetLatestHeight()-1
+			if err := hook.k.PruneSignersBelow(ctx, rollappId, stateInfo.GetLatestHeight()); err != nil {
+				return errorsmod.Wrap(err, "prune signers")
+			}
 		}
 		return nil
 	}

x/lightclient/keeper/keeper.go

@@ -130,6 +130,76 @@ shouldnt be allowed
 	return nil
 }
 
+// func (p *PairRange[K1, K2])
+type Foo[K1, K2 any] func(p *collections.PairRange[K1, K2], k2 K2) *collections.PairRange[K1, K2]
+
+// PruneSignersBelow PruneSigners removes bookkeeping for all heights BELOW h for given rollapp
+// This should only be called after canonical client set
+func (k Keeper) PruneSignersBelow(ctx sdk.Context, rollapp string, h uint64) error {
+	client, ok := k.GetCanonicalClient(ctx, rollapp)
+	if !ok {
+		return gerrc.ErrInternal.Wrap(`
+prune light client signers for rollapp before canonical client is set
+this suggests fork happened prior to genesis bridge completion, which
+shouldnt be allowed
+`)
+	}
+	rng := collections.NewPrefixedPairRange[string, uint64](client).EndExclusive(h)
+
+	seqs := make([]string, 0)
+	heights := make([]uint64, 0)
+
+	// collect first to avoid del while iterating
+	if err := k.clientHeightToSigner.Walk(ctx, rng, func(key collections.Pair[string, uint64], value string) (stop bool, err error) {
+		seqs = append(seqs, value)
+		heights = append(heights, key.K2())
+		return false, nil
+	}); err != nil {
+		return errorsmod.Wrap(err, "walk signers")
+	}
+
+	for i := 0; i < len(seqs); i++ {
+		if err := k.RemoveSigner(ctx, seqs[i], client, heights[i]); err != nil {
+			return errorsmod.Wrap(err, "remove signer")
+		}
+	}
+	return nil
+}
+
+// PruneSignersBelow PruneSigners removes bookkeeping for all heights BELOW h for given rollapp
+// This should only be called after canonical client set
+func (k Keeper) PruneGeneric(ctx sdk.Context, rollapp string, h uint64, f Foo[string, uint64]) error {
+	client, ok := k.GetCanonicalClient(ctx, rollapp)
+	if !ok {
+		return gerrc.ErrInternal.Wrap(`
+prune light client signers for rollapp before canonical client is set
+this suggests fork happened prior to genesis bridge completion, which
+shouldnt be allowed
+`)
+	}
+	//rng := collections.NewPrefixedPairRange[string, uint64](client)
+	rng := f(collections.NewPrefixedPairRange[string, uint64](client), h)
+
+	seqs := make([]string, 0)
+	heights := make([]uint64, 0)
+
+	// collect first to avoid del while iterating
+	if err := k.clientHeightToSigner.Walk(ctx, rng, func(key collections.Pair[string, uint64], value string) (stop bool, err error) {
+		seqs = append(seqs, value)
+		heights = append(heights, key.K2())
+		return false, nil
+	}); err != nil {
+		return errorsmod.Wrap(err, "walk signers")
+	}
+
+	for i := 0; i < len(seqs); i++ {
+		if err := k.RemoveSigner(ctx, seqs[i], client, heights[i]); err != nil {
+			return errorsmod.Wrap(err, "remove signer")
+		}
+	}
+	return nil
+}
+
 // GetSigner returns the sequencer address who signed the header in the update
 func (k Keeper) GetSigner(ctx sdk.Context, client string, h uint64) (string, error) {
 	return k.clientHeightToSigner.Get(ctx, collections.Join(client, h))

x/lightclient/keeper/keeper_test.go

@@ -72,3 +72,44 @@ func (s *TestSuite) TestUnbondConditionFlow() {
 	err = s.k().CanUnbond(s.Ctx, seq)
 	s.Require().NoError(err)
 }
+
+// Basic flow should prevent unbonding at appropriate times, and
+// handle pruning.
+func (s *TestSuite) TestPruneBelow() {
+	seq := keepertest.Alice
+
+	client := keepertest.CanonClientID
+
+	s.k().SetCanonicalClient(s.Ctx, seq.RollappId, client)
+
+	// allowed!
+	err := s.k().CanUnbond(s.Ctx, seq)
+	s.Require().NoError(err)
+
+	// add some unverified headers
+	for h := range 10 {
+		err := s.k().SaveSigner(s.Ctx, seq.Address, client, uint64(h))
+		s.Require().NoError(err)
+	}
+
+	// not allowed!
+	err = s.k().CanUnbond(s.Ctx, seq)
+	utest.IsErr(s.Require(), err, sequencertypes.ErrUnbondNotAllowed)
+
+	// we prune some, but still not allowed
+	err = s.k().PruneSignersBelow(s.Ctx, seq.RollappId, 6)
+	s.Require().NoError(err)
+
+	err = s.k().CanUnbond(s.Ctx, seq)
+	utest.IsErr(s.Require(), err, sequencertypes.ErrUnbondNotAllowed)
+
+	// the rest are verified
+	for h := 6; h < 10; h++ {
+		err := s.k().RemoveSigner(s.Ctx, seq.Address, client, uint64(h))
+		s.Require().NoError(err)
+	}
+
+	// allowed!
+	err = s.k().CanUnbond(s.Ctx, seq)
+	s.Require().NoError(err)
+}