Fix bug in pairs fallback resolving

freqtrade/configuration/configuration.py

@@ -380,7 +380,7 @@ class Configuration(object):
             config['pairs'].sort()
             return
 
-        if "config" in self.args:
+        if "config" in self.args and self.args.config:
             logger.info("Using pairlist from configuration.")
             config['pairs'] = config.get('exchange', {}).get('pair_whitelist')
         else:
@@ -388,3 +388,4 @@ class Configuration(object):
             pairs_file = Path(config['datadir']) / "pairs.json"
             if pairs_file.exists():
                 config['pairs'] = json_load(pairs_file)
+            config['pairs'].sort()

freqtrade/tests/test_configuration.py

@@ -792,3 +792,21 @@ def test_pairlist_resolving_with_config_pl_not_exists(mocker, default_conf):
     with pytest.raises(OperationalException, match=r"No pairs file found with path.*"):
         configuration = Configuration(args)
         configuration.get_config()
+
+
+def test_pairlist_resolving_fallback(mocker):
+    mocker.patch.object(Path, "exists", MagicMock(return_value=True))
+    mocker.patch("freqtrade.configuration.configuration.json_load",
+                 MagicMock(return_value=['XRP/BTC', 'ETH/BTC']))
+    arglist = [
+        'download-data',
+        '--exchange', 'binance'
+    ]
+
+    args = Arguments(arglist, '').get_parsed_arg()
+
+    configuration = Configuration(args)
+    config = configuration.get_config()
+
+    assert config['pairs'] == ['ETH/BTC', 'XRP/BTC']
+    assert config['exchange']['name'] == 'binance'