BUG: Account for commissions in Trade.pl and Trade.pl_pct (#1279)

* Apply Commissions to PnL.

* Account for Commissions in Trade.pl_pct.

Author: abhirathmahipal

backtesting/backtesting.py

@@ -671,15 +671,22 @@ def is_short(self):
 
     @property
     def pl(self):
-        """Trade profit (positive) or loss (negative) in cash units."""
+        """
+        Trade profit (positive) or loss (negative) in cash units.
+        Commissions are reflected only after the Trade is closed.
+        """
         price = self.__exit_price or self.__broker.last_price
-        return self.__size * (price - self.__entry_price)
+        return (self.__size * (price - self.__entry_price)) - self._commissions
 
     @property
     def pl_pct(self):
         """Trade profit (positive) or loss (negative) in percent."""
         price = self.__exit_price or self.__broker.last_price
-        return copysign(1, self.__size) * (price / self.__entry_price - 1)
+        gross_pl_pct = copysign(1, self.__size) * (price / self.__entry_price - 1)
+
+        # Total commission across the entire trade size to individual units
+        commission_pct = self._commissions / (abs(self.__size) * self.__entry_price)
+        return gross_pl_pct - commission_pct
 
     @property
     def value(self):