Turned amount into a computed property

freqtrade/persistence/models.py

@@ -280,7 +280,7 @@ class LocalTrade():
 
     @property
     def amount(self) -> float:
-        if self.leverage is not None:
+        if self._leverage is not None:
             return self._amount * self.leverage
         else:
             return self._amount
@@ -295,12 +295,6 @@ class LocalTrade():
 
     @leverage.setter
     def leverage(self, value):
-        # def set_leverage(self, lev: float, is_short: Optional[bool], amount: Optional[float]):
-        # TODO: Should this be @leverage.setter, or should it take arguments is_short and amount
-        # if is_short is None:
-        #     is_short = self.is_short
-        # if amount is None:
-        #     amount = self.amount
         if self.is_short is None or self.amount is None:
             raise OperationalException(
                 'LocalTrade.amount and LocalTrade.is_short must be assigned before assigning leverage')
@@ -308,12 +302,10 @@ class LocalTrade():
         self._leverage = value
         if self.is_short:
             # If shorting the full amount must be borrowed
-            self.borrowed = self.amount * value
+            self.borrowed = self._amount * value
         else:
             # If not shorting, then the trader already owns a bit
-            self.borrowed = self.amount * (value-1)
+            self.borrowed = self._amount * (value-1)
-        # TODO: Maybe amount should be a computed property, so we don't have to modify it
-        self.amount = self.amount * value
 
     # End of margin trading properties
 
@@ -878,7 +870,7 @@ class Trade(_DECL_BASE, LocalTrade):
     close_profit = Column(Float)
     close_profit_abs = Column(Float)
     stake_amount = Column(Float, nullable=False)
-    amount = Column(Float)
+    _amount = Column(Float)
     amount_requested = Column(Float)
     open_date = Column(DateTime, nullable=False, default=datetime.utcnow)
     close_date = Column(DateTime)

tests/test_persistence.py

@@ -105,6 +105,27 @@ def test_is_opening_closing_trade(fee):
     assert trade.is_closing_trade('sell') == False
 
 
+@pytest.mark.usefixtures("init_persistence")
+def test_amount(limit_buy_order, limit_sell_order, fee, caplog):
+    trade = Trade(
+        id=2,
+        pair='ETH/BTC',
+        stake_amount=0.001,
+        open_rate=0.01,
+        amount=5,
+        is_open=True,
+        open_date=arrow.utcnow().datetime,
+        fee_open=fee.return_value,
+        fee_close=fee.return_value,
+        exchange='binance',
+        is_short=False
+    )
+    assert trade.amount == 5
+    trade.leverage = 3
+    assert trade.amount == 15
+    assert trade._amount == 5
+
+
 @pytest.mark.usefixtures("init_persistence")
 def test_update_with_binance(limit_buy_order, limit_sell_order, fee, caplog):
     """