Merge pull request #1988 from freqtrade/fix/timeframes_crash

Gracefully fail on timeframes exception

freqtrade/exchange/exchange.py

@@ -269,6 +269,12 @@ class Exchange(object):
         """
         Checks if ticker interval from config is a supported timeframe on the exchange
         """
+        if not hasattr(self._api, "timeframes"):
+            # If timeframes is missing, the exchange probably has no fetchOHLCV method.
+            # Therefore we also show that.
+            raise OperationalException(
+                f"This exchange ({self.name}) does not have a `timeframes` attribute and "
+                f"is therefore not supported. fetchOHLCV: {self.exchange_has('fetchOHLCV')}")
         timeframes = self._api.timeframes
         if timeframe not in timeframes:
             raise OperationalException(

freqtrade/resolvers/exchange_resolver.py

@@ -28,6 +28,7 @@ class ExchangeResolver(IResolver):
         except ImportError:
             logger.info(
                 f"No {exchange_name} specific subclass found. Using the generic class instead.")
+        if not hasattr(self, "exchange"):
             self.exchange = Exchange(config)
 
     def _load_exchange(

freqtrade/tests/exchange/test_exchange.py

@@ -396,6 +396,23 @@ def test_validate_timeframes_failed(default_conf, mocker):
         Exchange(default_conf)
 
 
+def test_validate_timeframes_emulated_ohlcv(default_conf, mocker):
+    default_conf["ticker_interval"] = "3m"
+    api_mock = MagicMock()
+    id_mock = PropertyMock(return_value='test_exchange')
+    type(api_mock).id = id_mock
+
+    # delete timeframes so magicmock does not autocreate it
+    del api_mock.timeframes
+
+    mocker.patch('freqtrade.exchange.Exchange._init_ccxt', MagicMock(return_value=api_mock))
+    mocker.patch('freqtrade.exchange.Exchange._load_markets', MagicMock(return_value={}))
+    mocker.patch('freqtrade.exchange.Exchange.validate_pairs', MagicMock())
+    with pytest.raises(OperationalException,
+                       match=r'This exchange (.*) does not have a `timeframes` attribute and*'):
+        Exchange(default_conf)
+
+
 def test_validate_timeframes_not_in_config(default_conf, mocker):
     del default_conf["ticker_interval"]
     api_mock = MagicMock()