rpc: turn already downloaded into error in getblockfrompeer

Author: Sjors

src/rpc/blockchain.cpp

@@ -787,10 +787,7 @@ static RPCHelpMan getblockfrompeer()
             {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The block hash"},
             {"nodeid", RPCArg::Type::NUM, RPCArg::Optional::NO, "The node ID (see getpeerinfo for node IDs)"},
         },
-        RPCResult{RPCResult::Type::OBJ, "", "",
-        {
-            {RPCResult::Type::STR, "warnings", /*optional=*/true, "any warnings"},
-        }},
+        RPCResult{RPCResult::Type::OBJ_EMPTY, "", /*optional=*/ false, "", {}},
         RPCExamples{
             HelpExampleCli("getblockfrompeer", "\"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09\" 0")
             + HelpExampleRpc("getblockfrompeer", "\"00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09\" 0")
@@ -816,14 +813,14 @@ static RPCHelpMan getblockfrompeer()
         throw JSONRPCError(RPC_MISC_ERROR, "Block header missing");
     }
 
-    UniValue result = UniValue::VOBJ;
-
     if (index->nStatus & BLOCK_HAVE_DATA) {
-        result.pushKV("warnings", "Block already downloaded");
-    } else if (!peerman.FetchBlock(nodeid, *index)) {
+        throw JSONRPCError(RPC_MISC_ERROR, "Block already downloaded");
+    }
+
+    if (!peerman.FetchBlock(nodeid, *index)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Failed to fetch block from peer");
     }
-    return result;
+    return UniValue::VOBJ;
 },
     };
 }

test/functional/rpc_getblockfrompeer.py

@@ -61,12 +61,10 @@ def run_test(self):
         self.log.info("Successful fetch")
         result = self.nodes[0].getblockfrompeer(short_tip, peer_0_peer_1_id)
         self.wait_until(lambda: self.check_for_block(short_tip), timeout=1)
-        assert(not "warnings" in result)
+        assert_equal(result, {})
 
         self.log.info("Don't fetch blocks we already have")
-        result = self.nodes[0].getblockfrompeer(short_tip, peer_0_peer_1_id)
-        assert("warnings" in result)
-        assert_equal(result["warnings"], "Block already downloaded")
+        assert_raises_rpc_error(-1, "Block already downloaded", self.nodes[0].getblockfrompeer, short_tip, peer_0_peer_1_id)
 
 if __name__ == '__main__':
     GetBlockFromPeerTest().main()