Add warnings field to createmultisig to warn about uncompressed keys

Author: meshcollider

src/rpc/misc.cpp

@@ -113,6 +113,10 @@ static RPCHelpMan createmultisig()
                         {RPCResult::Type::STR, "address", "The value of the new multisig address."},
                         {RPCResult::Type::STR_HEX, "redeemScript", "The string value of the hex-encoded redemption script."},
                         {RPCResult::Type::STR, "descriptor", "The descriptor for this multisig"},
+                        {RPCResult::Type::ARR, "warnings", /* optional */ true, "Any warnings resulting from the creation of this multisig",
+                        {
+                            {RPCResult::Type::STR, "", ""},
+                        }},
                     }
                 },
                 RPCExamples{
@@ -161,6 +165,13 @@ static RPCHelpMan createmultisig()
     result.pushKV("redeemScript", HexStr(inner));
     result.pushKV("descriptor", descriptor->ToString());
 
+    UniValue warnings(UniValue::VARR);
+    if (!request.params[2].isNull() && OutputTypeFromDestination(dest) != output_type) {
+        // Only warns if the user has explicitly chosen an address type we cannot generate
+        warnings.push_back("Unable to make chosen address type, please ensure no uncompressed public keys are present.");
+    }
+    if (warnings.size()) result.pushKV("warnings", warnings);
+
     return result;
 },
     };

test/functional/rpc_createmultisig.py

@@ -78,8 +78,11 @@ def run_test(self):
             assert_equal(legacy_addr, wmulti0.addmultisigaddress(2, keys, '', 'legacy')['address'])
 
             # Generate addresses with the segwit types. These should all make legacy addresses
-            assert_equal(legacy_addr, wmulti0.createmultisig(2, keys, 'bech32')['address'])
-            assert_equal(legacy_addr, wmulti0.createmultisig(2, keys, 'p2sh-segwit')['address'])
+            for addr_type in ['bech32', 'p2sh-segwit']:
+                result = wmulti0.createmultisig(2, keys, addr_type)
+                assert_equal(legacy_addr, result['address'])
+                assert_equal(result['warnings'], ["Unable to make chosen address type, please ensure no uncompressed public keys are present."])
+
             assert_equal(legacy_addr, wmulti0.addmultisigaddress(2, keys, '', 'bech32')['address'])
             assert_equal(legacy_addr, wmulti0.addmultisigaddress(2, keys, '', 'p2sh-segwit')['address'])