chore: ignore claims behind last observed nonce (#1291)

# Related Github tickets

- VolumeFi#2160

# Background

If we ever reset the latest skyway nonce ahead of any observed claim, we
don't need nor want pigeons trying to attest to them. So, we can filter
claims that are behind the latest attested claim.

This should prevent pigeons from getting stuck trying to get old claims
if their RPC fails, and we need to reset the nonce ahead of observed
claims.

# Testing completed

- [x] test coverage exists or has been added/updated
- [x] tested in a private testnet

# Breaking changes

- [x] I have checked my code for breaking changes
- [x] If there are breaking changes, there is a supporting migration.

x/skyway/keeper/attestation.go

@@ -579,7 +579,11 @@ func (k Keeper) UnobservedBlocksByAddr(
 ) ([]uint64, error) {
 	lastCompassID := k.GetLatestCompassID(ctx, chainReferenceID)
 
-	var err error
+	lastObservedNonce, err := k.GetLastObservedSkywayNonce(ctx, chainReferenceID)
+	if err != nil {
+		return nil, err
+	}
+
 	var blocks []uint64
 
 	iterErr := k.IterateAttestations(ctx, chainReferenceID, false, func(_ []byte, att types.Attestation) bool {
@@ -602,6 +606,13 @@ func (k Keeper) UnobservedBlocksByAddr(
 			return false
 		}
 
+		// If we ever reset the latest skyway nonce ahead of any observed claim,
+		// we don't need nor want pigeons trying to attest to them. So, we can
+		// filter claims that are behind the latest attested claim.
+		if claim.GetSkywayNonce() <= lastObservedNonce {
+			return false
+		}
+
 		blocks = append(blocks, claim.GetEthBlockHeight())
 
 		return false

x/skyway/keeper/grpc_query_test.go

@@ -609,7 +609,7 @@ func TestGetUnobservedBlocksByAddr(t *testing.T) {
 			expected: nil,
 		},
 		{
-			name: "unobserved message already signed by validator",
+			name: "unobserved messages already signed by validator",
 			setup: func(ctx context.Context, k Keeper) {
 				sdkCtx := sdktypes.UnwrapSDKContext(ctx)
 
@@ -625,7 +625,7 @@ func TestGetUnobservedBlocksByAddr(t *testing.T) {
 					require.NoError(t, err)
 
 					att := &types.Attestation{
-						Observed: true,
+						Observed: false,
 						Votes:    []string{address},
 						Height:   uint64(sdkCtx.BlockHeight()),
 						Claim:    claim,
@@ -636,6 +636,37 @@ func TestGetUnobservedBlocksByAddr(t *testing.T) {
 			},
 			expected: nil,
 		},
+		{
+			name: "unobserved messages behind last observed nonce",
+			setup: func(ctx context.Context, k Keeper) {
+				sdkCtx := sdktypes.UnwrapSDKContext(ctx)
+
+				err := k.setLastObservedSkywayNonce(ctx, chainReferenceID, 2)
+				require.NoError(t, err)
+
+				for i := 0; i < 3; i++ {
+					msg := types.MsgLightNodeSaleClaim{
+						SkywayNonce:    uint64(i + 1),
+						EthBlockHeight: uint64(i + 1),
+					}
+					claim, err := codectypes.NewAnyWithValue(&msg)
+					require.NoError(t, err)
+
+					hash, err := msg.ClaimHash()
+					require.NoError(t, err)
+
+					att := &types.Attestation{
+						Observed: false,
+						Votes:    []string{},
+						Height:   uint64(sdkCtx.BlockHeight()),
+						Claim:    claim,
+					}
+
+					k.SetAttestation(ctx, chainReferenceID, uint64(i+1), hash, att)
+				}
+			},
+			expected: []uint64{3},
+		},
 		{
 			name: "unobserved messages for current and porevious compass",
 			setup: func(ctx context.Context, k Keeper) {