Merge #20536: wallet: Error with "Transaction too large" if the funded tx will end up being too large after signing

48a0319bab Add a test that selects too large if BnB is used (Andrew Chow)
3e69939b78 Fail if maximum weight is too large (Andrew Chow)
51e2cd322c Have CalculateMaximumSignedTxSize also compute tx weight (Andrew Chow)

Pull request description:

  Currently the `Transaction too large` is calculated on the transaction that is returned from `CreateTransaction`. This does not make sense for when `CreateTransaction` is being used for `fundrawtransaction` as no signing occurs so the final returned transaction is missing signatures. Thus users may successfully fund a transaction but fail to broadcast it after it has been fully signed.

  So instead we should figure out whether the transaction we are funding will be too large after it is signed. We can do this by having `CalculateMaximumSignedTxSize` also return the transaction weight and then comparing that weight against the maximum weight.

ACKs for top commit:
  instagibbs:
    ACK 48a0319bab
  meshcollider:
    utACK 48a0319bab
  Xekyo:
    utACK with nits 48a0319bab

Tree-SHA512: 1700c60b07f67e2d5c591c5ccd131ac9f1861fab3def961c3c9c4b3281ec1063fe8e4f0f7f1038cac72692340856406bcee8fb45c8104d2ad34357a0ec878ac7

test/functional/rpc_fundrawtransaction.py

@@ -94,6 +94,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         self.test_address_reuse()
         self.test_option_subtract_fee_from_outputs()
         self.test_subtract_fee_with_presets()
+        self.test_transaction_too_large()
 
     def test_change_position(self):
         """Ensure setting changePosition in fundraw with an exact match is handled properly."""
@@ -907,5 +908,24 @@ class RawTransactionsTest(BitcoinTestFramework):
         signedtx = self.nodes[0].signrawtransactionwithwallet(fundedtx['hex'])
         self.nodes[0].sendrawtransaction(signedtx['hex'])
 
+    def test_transaction_too_large(self):
+        self.log.info("Test fundrawtx where BnB solution would result in a too large transaction, but Knapsack would not")
+
+        self.nodes[0].createwallet("large")
+        wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+        recipient = self.nodes[0].get_wallet_rpc("large")
+        outputs = {}
+        rawtx = recipient.createrawtransaction([], {wallet.getnewaddress(): 147.99899260})
+
+        # Make 1500 0.1 BTC outputs
+        # The amount that we target for funding is in the BnB range when these outputs are used.
+        # However if these outputs are selected, the transaction will end up being too large, so it shouldn't use BnB and instead fallback to Knapsack
+        # but that behavior is not implemented yet. For now we just check that we get an error.
+        for i in range(0, 1500):
+            outputs[recipient.getnewaddress()] = 0.1
+        wallet.sendmany("", outputs)
+        self.nodes[0].generate(10)
+        assert_raises_rpc_error(-4, "Transaction too large", recipient.fundrawtransaction, rawtx)
+
 if __name__ == '__main__':
     RawTransactionsTest().main()