wallet.remove_transaction: also rm dependent/child txs

Main motivation is that I often use wallet.remove_transaction
from the Qt console, and would find this behaviour more intuitive.
Note that previously if one were to call this on a tx with children,
the crash reporter would appear with "wallet.get_history() failed balance sanity-check".

related: https://github.com/spesmilo/electrum/issues/6960#issuecomment-764716533

electrum/address_synchronizer.py

@@ -292,11 +292,7 @@ class AddressSynchronizer(Logger):
                     # this is a local tx that conflicts with non-local txns; drop.
                     return False
                 # keep this txn and remove all conflicting
-                to_remove = set()
-                to_remove |= conflicting_txns
-                for conflicting_tx_hash in conflicting_txns:
-                    to_remove |= self.get_depending_transactions(conflicting_tx_hash)
-                for tx_hash2 in to_remove:
+                for tx_hash2 in conflicting_txns:
                     self.remove_transaction(tx_hash2)
             # add inputs
             def add_value_from_prev_output():
@@ -342,6 +338,19 @@ class AddressSynchronizer(Logger):
             return True
 
     def remove_transaction(self, tx_hash: str) -> None:
+        """Removes a transaction AND all its dependents/children
+        from the wallet history.
+        """
+        with self.lock, self.transaction_lock:
+            to_remove = {tx_hash}
+            to_remove |= self.get_depending_transactions(tx_hash)
+            for txid in to_remove:
+                self._remove_transaction(txid)
+
+    def _remove_transaction(self, tx_hash: str) -> None:
+        """Removes a single transaction from the wallet history, and attempts
+         to undo all effects of the tx (spending inputs, creating outputs, etc).
+        """
         def remove_from_spent_outpoints():
             # undo spends in spent_outpoints
             if tx is not None:

electrum/commands.py

@@ -933,13 +933,10 @@ class Commands:
         if not is_hash256_str(txid):
             raise Exception(f"{repr(txid)} is not a txid")
         height = wallet.get_tx_height(txid).height
-        to_delete = {txid}
         if height != TX_HEIGHT_LOCAL:
             raise Exception(f'Only local transactions can be removed. '
                             f'This tx has height: {height} != {TX_HEIGHT_LOCAL}')
-        to_delete |= wallet.get_depending_transactions(txid)
-        for tx_hash in to_delete:
-            wallet.remove_transaction(tx_hash)
+        wallet.remove_transaction(txid)
         wallet.save_db()
 
     @command('wn')

electrum/gui/kivy/uix/dialogs/tx_dialog.py

@@ -348,17 +348,15 @@ class TxDialog(Factory.Popup):
 
     def remove_local_tx(self):
         txid = self.tx.txid()
-        to_delete = {txid}
-        to_delete |= self.wallet.get_depending_transactions(txid)
+        num_child_txs = len(self.wallet.get_depending_transactions(txid))
         question = _("Are you sure you want to remove this transaction?")
-        if len(to_delete) > 1:
+        if num_child_txs > 0:
             question = (_("Are you sure you want to remove this transaction and {} child transactions?")
-                        .format(len(to_delete) - 1))
+                        .format(num_child_txs))
 
         def on_prompt(b):
             if b:
-                for tx in to_delete:
-                    self.wallet.remove_transaction(tx)
+                self.wallet.remove_transaction(txid)
                 self.wallet.save_db()
                 self.app._trigger_update_wallet()  # FIXME private...
                 self.dismiss()

electrum/gui/qt/history_list.py

@@ -710,17 +710,15 @@ class HistoryList(MyTreeView, AcceptFileDragDrop):
         menu.exec_(self.viewport().mapToGlobal(position))
 
     def remove_local_tx(self, tx_hash: str):
-        to_delete = {tx_hash}
-        to_delete |= self.wallet.get_depending_transactions(tx_hash)
+        num_child_txs = len(self.wallet.get_depending_transactions(tx_hash))
         question = _("Are you sure you want to remove this transaction?")
-        if len(to_delete) > 1:
+        if num_child_txs > 0:
             question = (_("Are you sure you want to remove this transaction and {} child transactions?")
-                        .format(len(to_delete) - 1))
+                        .format(num_child_txs))
         if not self.parent.question(msg=question,
                                     title=_("Please confirm")):
             return
-        for tx in to_delete:
-            self.wallet.remove_transaction(tx)
+        self.wallet.remove_transaction(tx_hash)
         self.wallet.save_db()
         # need to update at least: history_list, utxo_list, address_list
         self.parent.need_update.set()