wallet: notify when preset + automatic inputs exceed max weight

This also avoids signing all inputs prior to erroring out.

Author: furszy

src/wallet/spend.cpp

@@ -799,6 +799,13 @@ util::Result<SelectionResult> SelectCoins(const CWallet& wallet, CoinsResult& av
         op_selection_result->RecalculateWaste(coin_selection_params.min_viable_change,
                                                 coin_selection_params.m_cost_of_change,
                                                 coin_selection_params.m_change_fee);
+
+        // Verify we haven't exceeded the maximum allowed weight
+        int max_inputs_weight = MAX_STANDARD_TX_WEIGHT - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
+        if (op_selection_result->GetWeight() > max_inputs_weight) {
+            return util::Error{_("The combination of the pre-selected inputs and the wallet automatic inputs selection exceeds the transaction maximum weight. "
+                                 "Please try sending a smaller amount or manually consolidating your wallet's UTXOs")};
+        }
     }
     return op_selection_result;
 }

test/functional/wallet_fundrawtransaction.py

@@ -114,6 +114,7 @@ def run_test(self):
         self.test_add_inputs_default_value()
         self.test_preset_inputs_selection()
         self.test_weight_calculation()
+        self.test_weight_limits()
         self.test_change_position()
         self.test_simple()
         self.test_simple_two_coins()
@@ -1312,6 +1313,38 @@ def test_weight_calculation(self):
 
         self.nodes[2].unloadwallet("test_weight_calculation")
 
+    def test_weight_limits(self):
+        self.log.info("Test weight limits")
+
+        self.nodes[2].createwallet("test_weight_limits")
+        wallet = self.nodes[2].get_wallet_rpc("test_weight_limits")
+
+        outputs = []
+        for _ in range(1472):
+            outputs.append({wallet.getnewaddress(address_type="legacy"): 0.1})
+        txid = self.nodes[0].send(outputs=outputs)["txid"]
+        self.generate(self.nodes[0], 1)
+
+        # 272 WU per input (273 when high-s); picking 1471 inputs will exceed the max standard tx weight.
+        rawtx = wallet.createrawtransaction([], [{wallet.getnewaddress(): 0.1 * 1471}])
+
+        # 1) Try to fund transaction only using the preset inputs
+        input_weights = []
+        for i in range(1471):
+            input_weights.append({"txid": txid, "vout": i, "weight": 273})
+        assert_raises_rpc_error(-4, "Transaction too large", wallet.fundrawtransaction, hexstring=rawtx, input_weights=input_weights)
+
+        # 2) Let the wallet fund the transaction
+        assert_raises_rpc_error(-4, "The inputs size exceeds the maximum weight. Please try sending a smaller amount or manually consolidating your wallet's UTXOs",
+                                wallet.fundrawtransaction, hexstring=rawtx)
+
+        # 3) Pre-select some inputs and let the wallet fill-up the remaining amount
+        inputs = input_weights[0:1000]
+        assert_raises_rpc_error(-4, "The combination of the pre-selected inputs and the wallet automatic inputs selection exceeds the transaction maximum weight. Please try sending a smaller amount or manually consolidating your wallet's UTXOs",
+                                wallet.fundrawtransaction, hexstring=rawtx, input_weights=inputs)
+
+        self.nodes[2].unloadwallet("test_weight_limits")
+
     def test_include_unsafe(self):
         self.log.info("Test fundrawtxn with unsafe inputs")
 

test/functional/wallet_send.py

@@ -577,5 +577,39 @@ def run_test(self):
         # but rounded to nearest integer, it should be the same as the target fee rate
         assert_equal(round(actual_fee_rate_sat_vb), target_fee_rate_sat_vb)
 
+        # Check tx creation size limits
+        self.test_weight_limits()
+
+    def test_weight_limits(self):
+        self.log.info("Test weight limits")
+
+        self.nodes[1].createwallet("test_weight_limits")
+        wallet = self.nodes[1].get_wallet_rpc("test_weight_limits")
+
+        # Generate future inputs; 272 WU per input (273 when high-s).
+        # Picking 1471 inputs will exceed the max standard tx weight.
+        outputs = []
+        for _ in range(1472):
+            outputs.append({wallet.getnewaddress(address_type="legacy"): 0.1})
+        self.nodes[0].send(outputs=outputs)
+        self.generate(self.nodes[0], 1)
+
+        # 1) Try to fund transaction only using the preset inputs
+        inputs = wallet.listunspent()
+        assert_raises_rpc_error(-4, "Transaction too large",
+                                wallet.send, outputs=[{wallet.getnewaddress(): 0.1 * 1471}], options={"inputs": inputs, "add_inputs": False})
+
+        # 2) Let the wallet fund the transaction
+        assert_raises_rpc_error(-4, "The inputs size exceeds the maximum weight. Please try sending a smaller amount or manually consolidating your wallet's UTXOs",
+                                wallet.send, outputs=[{wallet.getnewaddress(): 0.1 * 1471}])
+
+        # 3) Pre-select some inputs and let the wallet fill-up the remaining amount
+        inputs = inputs[0:1000]
+        assert_raises_rpc_error(-4, "The combination of the pre-selected inputs and the wallet automatic inputs selection exceeds the transaction maximum weight. Please try sending a smaller amount or manually consolidating your wallet's UTXOs",
+                                wallet.send, outputs=[{wallet.getnewaddress(): 0.1 * 1471}], options={"inputs": inputs, "add_inputs": True})
+
+        self.nodes[1].unloadwallet("test_weight_limits")
+
+
 if __name__ == '__main__':
     WalletSendTest().main()