Return error for Horizon.Problem in transaction_async request

clients/horizonclient/internal.go

@@ -27,10 +27,25 @@ func decodeResponse(resp *http.Response, object interface{}, horizonUrl string,
 	}
 	setCurrentServerTime(u.Hostname(), resp.Header["Date"], clock)
 
+	if resp.Request == nil || resp.Request.URL == nil || resp.Request.URL.Path != "/transactions_async" {
+		horizonError := &Error{
+			Response: resp,
+		}
+		decodeError := decoder.Decode(&horizonError.Problem)
+		if decodeError != nil {
+			err = decoder.Decode(&object)
+			if err != nil {
+				return errors.Wrap(err, "error decoding response")
+			}
+			return
+		}
+		return horizonError
+	}
+
 	// While this part of code assumes that any error < 200 or error >= 300 is a Horizon problem, it is not
 	// true for the response from /transactions_async endpoint which does give these codes for certain responses
 	// from core.
-	if !(resp.StatusCode >= 200 && resp.StatusCode < 300) && (resp.Request == nil || resp.Request.URL == nil || resp.Request.URL.Path != "/transactions_async") {
+	if !(resp.StatusCode >= 200 && resp.StatusCode < 300) {
 		horizonError := &Error{
 			Response: resp,
 		}

services/horizon/internal/integration/txsub_async_test.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 
 	"github.com/stellar/go/clients/horizonclient"
 	"github.com/stellar/go/protocols/horizon"
@@ -131,6 +132,32 @@ func TestAsyncTxSub_SubmissionTryAgainLater(t *testing.T) {
 	})
 }
 
+func TestAsyncTxSub_TransactionMalformed(t *testing.T) {
+	itest := integration.NewTest(t, integration.Config{
+		EnableSorobanRPC: true,
+		HorizonEnvironment: map[string]string{
+			"MAX_HTTP_REQUEST_SIZE": "1800",
+		},
+	})
+	master := itest.Master()
+
+	// establish which account will be contract owner, and load it's current seq
+	sourceAccount, err := itest.Client().AccountDetail(horizonclient.AccountRequest{
+		AccountID: itest.Master().Address(),
+	})
+	require.NoError(t, err)
+
+	installContractOp := assembleInstallContractCodeOp(t, itest.Master().Address(), "soroban_sac_test.wasm")
+	preFlightOp, minFee := itest.PreflightHostFunctions(&sourceAccount, *installContractOp)
+	txParams := integration.GetBaseTransactionParamsWithFee(&sourceAccount, minFee+txnbuild.MinBaseFee, &preFlightOp)
+	require.NoError(t, err)
+	_, err = itest.AsyncSubmitTransaction(master, txParams)
+	assert.EqualError(
+		t, err,
+		"horizon error: \"Transaction Malformed\" - check horizon.Error.Problem for more information",
+	)
+}
+
 func TestAsyncTxSub_GetOpenAPISpecResponse(t *testing.T) {
 	itest := integration.NewTest(t, integration.Config{})
 	res, err := http.Get(itest.AsyncTxSubOpenAPISpecURL())