wallet/wallet: refactor PublishTransaction to use unexported method

In this commit, we refactor the logic outside of PublishTransaction into
another unexported method. This will pave the road for unifying the
logic between SendOutputs and PublishTransaction.

wallet/wallet.go

@@ -3299,9 +3299,14 @@ func (w *Wallet) SignTransaction(tx *wire.MsgTx, hashType txscript.SigHashType,
 // This function is unstable and will be removed once syncing code is moved out
 // of the wallet.
 func (w *Wallet) PublishTransaction(tx *wire.MsgTx) error {
+	_, err := w.publishTransaction(tx)
+	return err
+}
+
+func (w *Wallet) publishTransaction(tx *wire.MsgTx) (*chainhash.Hash, error) {
 	server, err := w.requireChainClient()
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	// As we aim for this to be general reliable transaction broadcast API,
@@ -3310,19 +3315,19 @@ func (w *Wallet) PublishTransaction(tx *wire.MsgTx) error {
 	// set of records.
 	txRec, err := wtxmgr.NewTxRecordFromMsgTx(tx, time.Now())
 	if err != nil {
-		return err
+		return nil, err
 	}
 	err = walletdb.Update(w.db, func(dbTx walletdb.ReadWriteTx) error {
 		return w.addRelevantTx(dbTx, txRec, nil)
 	})
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	_, err = server.SendRawTransaction(tx, false)
+	txid, err := server.SendRawTransaction(tx, false)
 	switch {
 	case err == nil:
-		return nil
+		return txid, nil
 
 	// The following are errors returned from btcd's mempool.
 	case strings.Contains(err.Error(), "spent"):
@@ -3347,14 +3352,14 @@ func (w *Wallet) PublishTransaction(tx *wire.MsgTx) error {
 			return w.TxStore.RemoveUnminedTx(txmgrNs, txRec)
 		})
 		if dbErr != nil {
-			return fmt.Errorf("unable to broadcast tx: %v, "+
+			return nil, fmt.Errorf("unable to broadcast tx: %v, "+
 				"unable to remove invalid tx: %v", err, dbErr)
 		}
 
-		return err
+		return nil, err
 
 	default:
-		return err
+		return nil, err
 	}
 }