wallet: make sure payment requests are persisted

Fixes: after adding a payment request, if the process was killed,
the payreq might get lost. In case of using the GUI, neither the
callee nor the caller called wallet.save_db().

Unclear where wallet.save_db() should be called...
Now each method tries to persist their changes by default,
but as an optimisation, the caller can pass write_to_disk=False
e.g. when calling multiple such methods and then call wallet.save_db() itself.

If we had partial writes, which would either rm the need for wallet.save_db()
or at least make it cheaper, this code might get simpler...

related: https://github.com/spesmilo/electrum/pull/6435
related: https://github.com/spesmilo/electrum/issues/4823

electrum/commands.py

@@ -882,14 +882,12 @@ class Commands:
         expiration = int(expiration) if expiration else None
         req = wallet.make_payment_request(addr, amount, memo, expiration)
         wallet.add_payment_request(req)
-        wallet.save_db()
         return wallet.export_request(req)
 
     @command('wn')
     async def add_lightning_request(self, amount, memo='', expiration=3600, wallet: Abstract_Wallet = None):
         amount_sat = int(satoshis(amount))
         key = await wallet.lnworker._add_request_coro(amount_sat, memo, expiration)
-        wallet.save_db()
         return wallet.get_formatted_request(key)
 
     @command('w')
@@ -913,9 +911,7 @@ class Commands:
     @command('w')
     async def rmrequest(self, address, wallet: Abstract_Wallet = None):
         """Remove a payment request"""
-        result = wallet.remove_payment_request(address)
-        wallet.save_db()
-        return result
+        return wallet.remove_payment_request(address)
 
     @command('w')
     async def clear_requests(self, wallet: Abstract_Wallet = None):

electrum/lnworker.py

@@ -1697,7 +1697,9 @@ class LNWallet(LNWorker):
             self, *,
             amount_msat: Optional[int],
             message: str,
-            expiry: int) -> Tuple[LnAddr, str]:
+            expiry: int,
+            write_to_disk: bool = True,
+    ) -> Tuple[LnAddr, str]:
 
         timestamp = int(time.time())
         routing_hints = await self._calc_routing_hints_for_invoice(amount_msat)
@@ -1731,8 +1733,10 @@ class LNWallet(LNWorker):
             date=timestamp,
             payment_secret=derive_payment_secret_from_payment_preimage(payment_preimage))
         invoice = lnencode(lnaddr, self.node_keypair.privkey)
-        self.save_preimage(payment_hash, payment_preimage)
-        self.save_payment_info(info)
+        self.save_preimage(payment_hash, payment_preimage, write_to_disk=False)
+        self.save_payment_info(info, write_to_disk=False)
+        if write_to_disk:
+            self.wallet.save_db()
         return lnaddr, invoice
 
     async def _add_request_coro(self, amount_sat: Optional[int], message, expiry: int) -> str:
@@ -1740,17 +1744,21 @@ class LNWallet(LNWorker):
         lnaddr, invoice = await self.create_invoice(
             amount_msat=amount_msat,
             message=message,
-            expiry=expiry)
+            expiry=expiry,
+            write_to_disk=False,
+        )
         key = bh2u(lnaddr.paymenthash)
         req = LNInvoice.from_bech32(invoice)
-        self.wallet.add_payment_request(req)
+        self.wallet.add_payment_request(req, write_to_disk=False)
         self.wallet.set_label(key, message)
+        self.wallet.save_db()
         return key
 
-    def save_preimage(self, payment_hash: bytes, preimage: bytes):
+    def save_preimage(self, payment_hash: bytes, preimage: bytes, *, write_to_disk: bool = True):
         assert sha256(preimage) == payment_hash
         self.preimages[bh2u(payment_hash)] = bh2u(preimage)
-        self.wallet.save_db()
+        if write_to_disk:
+            self.wallet.save_db()
 
     def get_preimage(self, payment_hash: bytes) -> Optional[bytes]:
         r = self.preimages.get(bh2u(payment_hash))
@@ -1764,12 +1772,13 @@ class LNWallet(LNWorker):
                 amount_msat, direction, status = self.payments[key]
                 return PaymentInfo(payment_hash, amount_msat, direction, status)
 
-    def save_payment_info(self, info: PaymentInfo) -> None:
+    def save_payment_info(self, info: PaymentInfo, *, write_to_disk: bool = True) -> None:
         key = info.payment_hash.hex()
         assert info.status in SAVED_PR_STATUS
         with self.lock:
             self.payments[key] = info.amount_msat, info.direction, info.status
-        self.wallet.save_db()
+        if write_to_disk:
+            self.wallet.save_db()
 
     def check_received_mpp_htlc(self, payment_secret, short_channel_id, htlc: UpdateAddHtlc, expected_msat: int) -> Optional[bool]:
         """ return MPP status: True (accepted), False (expired) or None """

electrum/wallet.py

@@ -2295,11 +2295,13 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
             key = req.rhash
         return key
 
-    def add_payment_request(self, req: Invoice):
+    def add_payment_request(self, req: Invoice, *, write_to_disk: bool = True):
         key = self.get_key_for_receive_request(req, sanity_checks=True)
         message = req.message
         self.receive_requests[key] = req
         self.set_label(key, message)  # should be a default label
+        if write_to_disk:
+            self.save_db()
         return req
 
     def delete_request(self, key):
@@ -2316,11 +2318,13 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
         elif self.lnworker:
             self.lnworker.delete_payment(key)
 
-    def remove_payment_request(self, addr):
-        if addr not in self.receive_requests:
-            return False
-        self.receive_requests.pop(addr)
-        return True
+    def remove_payment_request(self, addr) -> bool:
+        found = False
+        if addr in self.receive_requests:
+            found = True
+            self.receive_requests.pop(addr)
+            self.save_db()
+        return found
 
     def get_sorted_requests(self) -> List[Invoice]:
         """ sorted by timestamp """