From 758743c7aa85c77bf1676556f4434523f0d7b7ed Mon Sep 17 00:00:00 2001
From: "Masih H. Derkani" <m@derkani.org>
Date: Thu, 4 Sep 2025 10:34:59 +0100
Subject: [PATCH 1/3] Return error if any in mempool `CheckTx` and fix callback

When call to the underlying (cosmos) `CheckTx` fails make sure that the
error is returned from mempool `CheckTx`.

Fix check for callback to assure result is non-nil before callback
function is executed.
---
 internal/mempool/mempool.go | 41 ++++++++++++++++++-------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/internal/mempool/mempool.go b/internal/mempool/mempool.go
index a078e7865..8839ca9ad 100644
--- a/internal/mempool/mempool.go
+++ b/internal/mempool/mempool.go
@@ -363,6 +363,7 @@ func (txmp *TxMempool) CheckTx(
 	if err != nil {
 		removeHandler(true)
 		res.Log = txmp.AppendCheckTxErr(res.Log, err.Error())
+		return err
 	}
 
 	wtx := &WrappedTx{
@@ -377,27 +378,25 @@ func (txmp *TxMempool) CheckTx(
 		estimatedGas:  res.GasEstimated,
 	}
 
-	if err == nil {
-		// only add new transaction if checkTx passes and is not pending
-		if !res.IsPendingTransaction {
-			err = txmp.addNewTransaction(wtx, res.ResponseCheckTx, txInfo)
-			if err != nil {
-				return err
-			}
-		} else {
-			// otherwise add to pending txs store
-			if res.Checker == nil {
-				return errors.New("no checker available for pending transaction")
-			}
-			if err := txmp.canAddPendingTx(wtx); err != nil {
-				// TODO: eviction strategy for pending transactions
-				removeHandler(true)
-				return err
-			}
-			atomic.AddInt64(&txmp.pendingSizeBytes, int64(wtx.Size()))
-			if err := txmp.pendingTxs.Insert(wtx, res, txInfo); err != nil {
-				return err
-			}
+	// only add new transaction if checkTx passes and is not pending
+	if !res.IsPendingTransaction {
+		err = txmp.addNewTransaction(wtx, res.ResponseCheckTx, txInfo)
+		if err != nil {
+			return err
+		}
+	} else {
+		// otherwise add to pending txs store
+		if res.Checker == nil {
+			return errors.New("no checker available for pending transaction")
+		}
+		if err := txmp.canAddPendingTx(wtx); err != nil {
+			// TODO: eviction strategy for pending transactions
+			removeHandler(true)
+			return err
+		}
+		atomic.AddInt64(&txmp.pendingSizeBytes, int64(wtx.Size()))
+		if err := txmp.pendingTxs.Insert(wtx, res, txInfo); err != nil {
+			return err
 		}
 	}
 

From e139fc91f987c40b125801fc88840109cb80878b Mon Sep 17 00:00:00 2001
From: "Masih H. Derkani" <m@derkani.org>
Date: Thu, 4 Sep 2025 14:15:33 +0100
Subject: [PATCH 2/3] Increment pending size only if insertion is successful

---
 internal/mempool/mempool.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/mempool/mempool.go b/internal/mempool/mempool.go
index 8839ca9ad..2bd6296eb 100644
--- a/internal/mempool/mempool.go
+++ b/internal/mempool/mempool.go
@@ -394,10 +394,10 @@ func (txmp *TxMempool) CheckTx(
 			removeHandler(true)
 			return err
 		}
-		atomic.AddInt64(&txmp.pendingSizeBytes, int64(wtx.Size()))
 		if err := txmp.pendingTxs.Insert(wtx, res, txInfo); err != nil {
 			return err
 		}
+		atomic.AddInt64(&txmp.pendingSizeBytes, int64(wtx.Size()))
 	}
 
 	if cb != nil {

From 7ae635d7524d135829b938f561ccf5b91b4dfe51 Mon Sep 17 00:00:00 2001
From: "Masih H. Derkani" <m@derkani.org>
Date: Fri, 5 Sep 2025 09:06:44 +0100
Subject: [PATCH 3/3] Remove unnecessary error log add and fix nil check

---
 internal/mempool/mempool.go | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/internal/mempool/mempool.go b/internal/mempool/mempool.go
index 2bd6296eb..767c712db 100644
--- a/internal/mempool/mempool.go
+++ b/internal/mempool/mempool.go
@@ -355,14 +355,13 @@ func (txmp *TxMempool) CheckTx(
 		if removeFromCache {
 			txmp.cache.Remove(txHash)
 		}
-		if res.ExpireTxHandler != nil {
+		if res != nil && res.ExpireTxHandler != nil {
 			res.ExpireTxHandler()
 		}
 	}
 
 	if err != nil {
 		removeHandler(true)
-		res.Log = txmp.AppendCheckTxErr(res.Log, err.Error())
 		return err
 	}