fix!: Share splitting bug v0.11.0 (#1109)

## Overview

fixes the bug described in #1108

the modified tests fails on v0.10.x

## Checklist

- [x] New and updated code has appropriate documentation
- [x] New and updated code has new and/or updated testing
- [x] Required CI checks are passing
- [x] Visual proof for any user facing features like CLI or
documentation updates
- [x] Linked issues closed with keywords

app/test/fuzz_abci_test.go

@@ -25,29 +25,37 @@ func TestFuzzPrepareProcessProposal(t *testing.T) {
 	encConf := encoding.MakeConfig(app.ModuleEncodingRegisters...)
 	signer := testutil.GenerateKeyringSigner(t, testAccName)
 	testApp := testutil.SetupTestAppWithGenesisValSet(t)
-	timer := time.After(time.Second * 30)
-	for {
-		select {
-		case <-timer:
-			return
-		default:
-			t.Run("randomized inputs to Prepare and Process Proposal", func(t *testing.T) {
-				pfdTxs := paytestutil.GenerateManyRawWirePFD(t, encConf.TxConfig, signer, tmrand.Intn(100), -1)
-				txs := paytestutil.GenerateManyRawSendTxs(t, encConf.TxConfig, signer, tmrand.Intn(20))
-				txs = append(txs, pfdTxs...)
-				resp := testApp.PrepareProposal(abci.RequestPrepareProposal{
-					BlockData: &core.Data{
-						Txs: txs,
-					},
-				})
-				res := testApp.ProcessProposal(abci.RequestProcessProposal{
-					BlockData: resp.BlockData,
-					Header: core.Header{
-						DataHash: resp.BlockData.Hash,
-					},
+	timer := time.After(time.Minute * 1)
+
+	type test struct {
+		count, size int
+	}
+	tests := []test{{10000, 400}, {100, -1}}
+
+	for _, tt := range tests {
+		for {
+			select {
+			case <-timer:
+				return
+			default:
+				t.Run("randomized inputs to Prepare and Process Proposal", func(t *testing.T) {
+					pfdTxs := paytestutil.GenerateManyRawWirePFD(t, encConf.TxConfig, signer, tmrand.Intn(tt.count), tt.size)
+					txs := paytestutil.GenerateManyRawSendTxs(t, encConf.TxConfig, signer, tmrand.Intn(20))
+					txs = append(txs, pfdTxs...)
+					resp := testApp.PrepareProposal(abci.RequestPrepareProposal{
+						BlockData: &core.Data{
+							Txs: txs,
+						},
+					})
+					res := testApp.ProcessProposal(abci.RequestProcessProposal{
+						BlockData: resp.BlockData,
+						Header: core.Header{
+							DataHash: resp.BlockData.Hash,
+						},
+					})
+					require.Equal(t, abci.ResponseProcessProposal_ACCEPT, res.Result)
 				})
-				require.Equal(t, abci.ResponseProcessProposal_ACCEPT, res.Result)
-			})
+			}
 		}
 	}
 }

pkg/shares/share_splitting.go

@@ -51,6 +51,12 @@ func Split(data coretypes.Data, useShareIndexes bool) ([]Share, error) {
 			MsgSharesUsed(len(data.Messages.MessagesList[0].Data)),
 			int(data.OriginalSquareSize),
 		)
+
+		// force msgIndexes to be the first share index
+		if len(msgIndexes) != 0 && useShareIndexes {
+			msgShareStart = int(msgIndexes[0])
+		}
+
 		ns := appconsts.TxNamespaceID
 		if len(evdShares) > 0 {
 			ns = appconsts.EvidenceNamespaceID