From 1698d968834df46b053fd500f79c5a030132000f Mon Sep 17 00:00:00 2001
From: Matthias <xmatthias@outlook.com>
Date: Sat, 12 Oct 2024 18:20:26 +0200
Subject: [PATCH] feat: Allow Backtesting to reverse position

---
 freqtrade/optimize/backtesting.py | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/freqtrade/optimize/backtesting.py b/freqtrade/optimize/backtesting.py
index 03c7bcccc..14a63fb52 100644
--- a/freqtrade/optimize/backtesting.py
+++ b/freqtrade/optimize/backtesting.py
@@ -1335,11 +1335,38 @@ class Backtesting:
         trade_dir: Optional[LongShort],
         can_enter: bool,
     ) -> None:
+        """
+        Conditionally call backtest_loop_inner a 2nd time if shorting is enabled,
+         a position closed and a new signal in the other direction is available.
+        """
+        if not self._can_short or trade_dir is None:
+            # No need to reverse position if shorting is disabled or there's no new signal
+            self.backtest_loop_inner(row, pair, current_time, trade_dir, can_enter)
+        else:
+            for _ in (0, 1):
+                a = self.backtest_loop_inner(row, pair, current_time, trade_dir, can_enter)
+                if not a or a == trade_dir:
+                    # the trade didn't close or position change is in the same direction
+                    break
+
+    def backtest_loop_inner(
+        self,
+        row: tuple,
+        pair: str,
+        current_time: datetime,
+        trade_dir: Optional[LongShort],
+        can_enter: bool,
+    ) -> Optional[LongShort]:
         """
         NOTE: This method is used by Hyperopt at each iteration. Please keep it optimized.
 
         Backtesting processing for one candle/pair.
         """
+        exiting_dir: Optional[LongShort] = None
+        if not self._position_stacking and len(LocalTrade.bt_trades_open_pp[pair]) > 0:
+            # position_stacking not supported for now.
+            exiting_dir = "short" if LocalTrade.bt_trades_open_pp[pair][0].is_short else "long"
+
         for t in list(LocalTrade.bt_trades_open_pp[pair]):
             # 1. Manage currently open orders of active trades
             if self.manage_open_orders(t, current_time, row):
@@ -1380,6 +1407,10 @@ class Backtesting:
             if order:
                 self._process_exit_order(order, trade, current_time, row, pair)
 
+        if exiting_dir and len(LocalTrade.bt_trades_open_pp[pair]) == 0:
+            return exiting_dir
+        return None
+
     def time_pair_generator(
         self, start_date: datetime, end_date: datetime, increment: timedelta, pairs: list[str]
     ):