From a0f46bf9b8e729784f7444b3cc9dfffcd1b519b3 Mon Sep 17 00:00:00 2001
From: c9s <yoan@maicoin.com>
Date: Wed, 8 Dec 2021 23:30:58 +0800
Subject: [PATCH] improve error checking, avoid using panic inside the
 constructor

---
 pkg/backtest/exchange.go | 16 ++++++++--------
 pkg/cmd/backtest.go      |  6 +++++-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/pkg/backtest/exchange.go b/pkg/backtest/exchange.go
index d7e2c60ad..177b51a78 100644
--- a/pkg/backtest/exchange.go
+++ b/pkg/backtest/exchange.go
@@ -70,29 +70,29 @@ type Exchange struct {
 	doneC   chan struct{}
 }
 
-func NewExchange(sourceName types.ExchangeName, srv *service.BacktestService, config *bbgo.Backtest) *Exchange {
+func NewExchange(sourceName types.ExchangeName, srv *service.BacktestService, config *bbgo.Backtest) (*Exchange, error) {
 	ex, err := newPublicExchange(sourceName)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	if config == nil {
-		panic(errors.New("backtest config can not be nil"))
+		return nil, errors.New("backtest config can not be nil")
 	}
 
 	markets, err := bbgo.LoadExchangeMarketsWithCache(context.Background(), ex)
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	startTime, err := config.ParseStartTime()
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	endTime, err := config.ParseEndTime()
 	if err != nil {
-		panic(err)
+		return nil, err
 	}
 
 	account := &types.Account{
@@ -119,7 +119,7 @@ func NewExchange(sourceName types.ExchangeName, srv *service.BacktestService, co
 	}
 
 	e.resetMatchingBooks()
-	return e
+	return e, nil
 }
 
 func (e *Exchange) addTrade(trade types.Trade) {
@@ -321,5 +321,5 @@ func newPublicExchange(sourceExchange types.ExchangeName) (types.Exchange, error
 		return okex.New("", "", ""), nil
 	}
 
-	return nil, fmt.Errorf("exchange %s is not supported", sourceExchange)
+	return nil, fmt.Errorf("public data from exchange %s is not supported", sourceExchange)
 }
diff --git a/pkg/cmd/backtest.go b/pkg/cmd/backtest.go
index e2cfbb41a..0b3999c4d 100644
--- a/pkg/cmd/backtest.go
+++ b/pkg/cmd/backtest.go
@@ -261,7 +261,11 @@ var BacktestCmd = &cobra.Command{
 			}
 		}
 
-		backtestExchange := backtest.NewExchange(exchangeName, backtestService, userConfig.Backtest)
+		backtestExchange, err := backtest.NewExchange(exchangeName, backtestService, userConfig.Backtest)
+		if err != nil {
+			return errors.Wrap(err, "failed to create backtest exchange")
+		}
+
 		environ.SetStartTime(startTime)
 		environ.AddExchange(exchangeName.String(), backtestExchange)