chore: ignore claims behind last observed nonce

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.

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) {