Add loading order_types from config file

config_full.json.example

@@ -33,6 +33,11 @@
         "order_book_min": 1,
         "order_book_max": 9
     },
+    "order_types": {
+        "buy": "limit",
+        "sell": "limit",
+        "stoploss": "market"
+    },
     "exchange": {
         "name": "bittrex",
         "key": "your_exchange_key",

freqtrade/strategy/resolver.py

@@ -75,6 +75,15 @@ class StrategyResolver(object):
         else:
             config['process_only_new_candles'] = self.strategy.process_only_new_candles
 
+        if 'order_types' in config:
+            self.strategy.order_types = config['order_types']
+            logger.info(
+                "Override strategy 'order_types' with value in config file: %s.",
+                config['order_types']
+            )
+        else:
+            config['order_types'] = self.strategy.order_types
+
         # Sort and apply type conversions
         self.strategy.minimal_roi = OrderedDict(sorted(
             {int(key): value for (key, value) in self.strategy.minimal_roi.items()}.items(),

freqtrade/tests/strategy/test_strategy.py

@@ -182,6 +182,32 @@ def test_strategy_override_process_only_new_candles(caplog):
             ) in caplog.record_tuples
 
 
+def test_strategy_override_order_types(caplog):
+    caplog.set_level(logging.INFO)
+
+    order_types = {
+        'buy': 'market',
+        'sell': 'limit',
+        'stoploss': 'limit'
+    }
+
+    config = {
+        'strategy': 'DefaultStrategy',
+        'order_types': order_types
+    }
+    resolver = StrategyResolver(config)
+
+    assert resolver.strategy.order_types
+    for method in ['buy', 'sell', 'stoploss']:
+        assert resolver.strategy.order_types[method] == order_types[method]
+
+    assert ('freqtrade.strategy.resolver',
+            logging.INFO,
+            "Override strategy 'order_types' with value in config file:"
+            " {'buy': 'market', 'sell': 'limit', 'stoploss': 'limit'}."
+            ) in caplog.record_tuples
+
+
 def test_deprecate_populate_indicators(result):
     default_location = path.join(path.dirname(path.realpath(__file__)))
     resolver = StrategyResolver({'strategy': 'TestStrategyLegacy',