fixed txpool maxEnqueued issue (#1789)

* fixed txpool maxEnqueued issue

* removed extra space

txpool/txpool.go

@@ -814,7 +814,7 @@ func (p *TxPool) addTx(origin txOrigin, tx *types.Transaction) error {
 
 		slotsFree += slotsRequired(oldTxWithSameNonce) // add old tx slots
 	} else {
-		if account.enqueued.length() == account.maxEnqueued {
+		if account.enqueued.length() == account.maxEnqueued && tx.Nonce != accountNonce {
 			return ErrMaxEnqueuedLimitReached
 		}
 

txpool/txpool_test.go

@@ -768,6 +768,43 @@ func TestEnqueueHandler(t *testing.T) {
 			acc.nonceToTx.unlock()
 		},
 	)
+
+	t.Run(
+		"accept new tx with nextNonce when enqueued is full",
+		func(t *testing.T) {
+			t.Parallel()
+
+			pool, err := newTestPool()
+			assert.NoError(t, err)
+			pool.SetSigner(&mockSigner{})
+
+			// mock full enqueued
+			pool.accounts.maxEnqueuedLimit = 10
+
+			// add 10 transaction in txpool i.e. max enqueued transactions
+			for i := uint64(1); i <= 10; i++ {
+				err := pool.addTx(local, newTx(addr1, i, 1))
+				assert.NoError(t, err)
+			}
+
+			assert.Equal(t, uint64(10), pool.accounts.get(addr1).enqueued.length())
+			assert.Equal(t, uint64(0), pool.accounts.get(addr1).promoted.length())
+			assert.Equal(t, uint64(0), pool.accounts.get(addr1).getNonce())
+
+			err = pool.addTx(local, newTx(addr1, 11, 1))
+			assert.True(t, errors.Is(err, ErrMaxEnqueuedLimitReached))
+
+			// add the transaction with nextNonce i.e. nonce=0
+			err = pool.addTx(local, newTx(addr1, uint64(0), 1))
+			assert.NoError(t, err)
+
+			pool.handlePromoteRequest(<-pool.promoteReqCh)
+
+			assert.Equal(t, uint64(0), pool.accounts.get(addr1).enqueued.length())
+			assert.Equal(t, uint64(11), pool.accounts.get(addr1).promoted.length())
+			assert.Equal(t, uint64(11), pool.accounts.get(addr1).getNonce())
+		},
+	)
 }
 
 func TestAddTx(t *testing.T) {