Only allow min-stake adjustments of up to 30%

fix #5856

docs/configuration.md

@@ -214,7 +214,7 @@ With a reserve of 5%, the minimum stake amount would be ~12.6$ (`12 * (1 + 0.05)
 To limit this calculation in case of large stoploss values, the calculated minimum stake-limit will never be more than 50% above the real limit.
 
 !!! Warning
-    Since the limits on exchanges are usually stable and are not updated often, some pairs can show pretty high minimum limits, simply because the price increased a lot since the last limit adjustment by the exchange.
+    Since the limits on exchanges are usually stable and are not updated often, some pairs can show pretty high minimum limits, simply because the price increased a lot since the last limit adjustment by the exchange. Freqtrade adjusts the stake-amount to this value, unless it's > 30% more than the calculated/desired stake-amount - in which case the trade is rejected.
 
 #### Tradable balance
 

freqtrade/wallets.py

@@ -255,6 +255,15 @@ class Wallets:
                     f"Stake amount for pair {pair} is too small "
                     f"({stake_amount} < {min_stake_amount}), adjusting to {min_stake_amount}."
                 )
+            if stake_amount * 1.3 < min_stake_amount:
+                # Top-cap stake-amount adjustments to +30%.
+                if self._log:
+                    logger.info(
+                        f"Adjusted stake amount for pair {pair} is more than 30% bigger than "
+                        f"the desired stake ({stake_amount} * 1.3 > {max_stake_amount}), "
+                        f"ignoring trade."
+                    )
+                return 0
             stake_amount = min_stake_amount
 
         if stake_amount > max_stake_amount:

tests/test_freqtradebot.py

@@ -321,7 +321,7 @@ def test_create_trade_no_stake_amount(default_conf_usdt, ticker_usdt, fee, mocke
 
 @pytest.mark.parametrize('stake_amount,create,amount_enough,max_open_trades', [
     (5.0, True, True, 99),
-    (0.00005, True, False, 99),
+    (0.04, True, False, 99), # Amount will be adjusted to min - which is 0.051
     (0, False, True, 99),
     (UNLIMITED_STAKE_AMOUNT, False, True, 0),
 ])

tests/test_wallets.py

@@ -185,8 +185,9 @@ def test_get_trade_stake_amount_unlimited_amount(default_conf, ticker, balance_r
     (100, 11, 500, 100),
     (1000, 11, 500, 500),  # Above max-stake
     (20, 15, 10, 0),  # Minimum stake > max-stake
-    (1, 11, 100, 11),  # Below min stake
+    (9, 11, 100, 11),  # Below min stake
     (1, 15, 10, 0),  # Below min stake and min_stake > max_stake
+    (20, 50, 100, 0),  # Below min stake and stake * 1.3 > min_stake
 
 ])
 def test_validate_stake_amount(mocker, default_conf,