Add deep_merge for _ft_has and test

freqtrade/exchange/exchange.py

@@ -2,23 +2,24 @@
 """
 Cryptocurrency Exchanges support
 """
-import logging
+import asyncio
 import inspect
-from random import randint
-from typing import List, Dict, Tuple, Any, Optional
+import logging
+from copy import deepcopy
 from datetime import datetime
-from math import floor, ceil
+from math import ceil, floor
+from random import randint
+from typing import Any, Dict, List, Optional, Tuple
 
 import arrow
-import asyncio
 import ccxt
 import ccxt.async_support as ccxt_async
 from pandas import DataFrame
 
-from freqtrade import (constants, DependencyException, OperationalException,
-                       TemporaryError, InvalidOrderException)
+from freqtrade import (DependencyException, InvalidOrderException,
+                       OperationalException, TemporaryError, constants)
 from freqtrade.data.converter import parse_ticker_dataframe
-
+from freqtrade.misc import deep_merge_dicts
 
 logger = logging.getLogger(__name__)
 
@@ -68,12 +69,13 @@ class Exchange(object):
     _params: Dict = {}
 
     # Dict to specify which options each exchange implements
-    # TODO: this should be merged with attributes from subclasses
-    # To avoid having to copy/paste this to all subclasses.
-    _ft_has: Dict = {
+    # This defines defaults, which can be selectively overridden by subclasses using _ft_has
+    # or by specifying them in the configuration.
+    _ft_has_default: Dict = {
         "stoploss_on_exchange": False,
         "order_time_in_force": ["gtc"],
     }
+    _ft_has: Dict = {}
 
     def __init__(self, config: dict) -> None:
         """
@@ -100,6 +102,13 @@ class Exchange(object):
             logger.info('Instance is running with dry_run enabled')
 
         exchange_config = config['exchange']
+
+        # Deep merge ft_has with default ft_has options
+        self._ft_has = deep_merge_dicts(self._ft_has, deepcopy(self._ft_has_default))
+        if exchange_config.get("_ft_has_params"):
+            self._ft_has = deep_merge_dicts(exchange_config.get("_ft_has_params"),
+                                            self._ft_has)
+
         self._api: ccxt.Exchange = self._init_ccxt(
             exchange_config, ccxt_kwargs=exchange_config.get('ccxt_config'))
         self._api_async: ccxt_async.Exchange = self._init_ccxt(