rpc: Add "jsonrpc" field and drop null "result"/"error" fields

Only for JSON-RPC 2.0 requests.

6 files changed, 28 insertions, 18 deletions

diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
index 3591f7248b..0bafb4f645 100644
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -302,7 +302,7 @@ public:
         }
         addresses.pushKV("total", total);
         result.pushKV("addresses_known", addresses);
-        return JSONRPCReplyObj(std::move(result), NullUniValue, 1);
+        return JSONRPCReplyObj(std::move(result), NullUniValue, /*id=*/1, JSONRPCVersion::V1_LEGACY);
     }
 };
 
@@ -371,7 +371,7 @@ public:
         }
         result.pushKV("relayfee", batch[ID_NETWORKINFO]["result"]["relayfee"]);
         result.pushKV("warnings", batch[ID_NETWORKINFO]["result"]["warnings"]);
-        return JSONRPCReplyObj(std::move(result), NullUniValue, 1);
+        return JSONRPCReplyObj(std::move(result), NullUniValue,  /*id=*/1, JSONRPCVersion::V1_LEGACY);
     }
 };
 
@@ -623,7 +623,7 @@ public:
             }
         }
 
-        return JSONRPCReplyObj(UniValue{result}, NullUniValue, 1);
+        return JSONRPCReplyObj(UniValue{result}, NullUniValue, /*id=*/1, JSONRPCVersion::V1_LEGACY);
     }
 
     const std::string m_help_doc{
@@ -709,7 +709,7 @@ public:
         UniValue result(UniValue::VOBJ);
         result.pushKV("address", address_str);
         result.pushKV("blocks", reply.get_obj()["result"]);
-        return JSONRPCReplyObj(std::move(result), NullUniValue, 1);
+        return JSONRPCReplyObj(std::move(result), NullUniValue, /*id=*/1, JSONRPCVersion::V1_LEGACY);
     }
 protected:
     std::string address_str;
diff --git a/src/httprpc.cpp b/src/httprpc.cpp
index 53f994efd7..817c75f3b5 100644
--- a/src/httprpc.cpp
+++ b/src/httprpc.cpp
@@ -73,7 +73,7 @@ static std::vector<std::vector<std::string>> g_rpcauth;
 static std::map<std::string, std::set<std::string>> g_rpc_whitelist;
 static bool g_rpc_whitelist_default = false;
 
-static void JSONErrorReply(HTTPRequest* req, UniValue objError, UniValue id)
+static void JSONErrorReply(HTTPRequest* req, UniValue objError, const JSONRPCRequest& jreq)
 {
     // Send error reply from json-rpc error object
     int nStatus = HTTP_INTERNAL_SERVER_ERROR;
@@ -84,7 +84,7 @@ static void JSONErrorReply(HTTPRequest* req, UniValue objError, UniValue id)
     else if (code == RPC_METHOD_NOT_FOUND)
         nStatus = HTTP_NOT_FOUND;
 
-    std::string strReply = JSONRPCReplyObj(NullUniValue, std::move(objError), std::move(id)).write() + "\n";
+    std::string strReply = JSONRPCReplyObj(NullUniValue, std::move(objError), jreq.id, jreq.m_json_version).write() + "\n";
 
     req->WriteHeader("Content-Type", "application/json");
     req->WriteReply(nStatus, strReply);
@@ -231,9 +231,9 @@ static bool HTTPReq_JSONRPC(const std::any& context, HTTPRequest* req)
                     jreq.parse(valRequest[i]);
                     reply.push_back(JSONRPCExec(jreq));
                 } catch (UniValue& e) {
-                    reply.push_back(JSONRPCReplyObj(NullUniValue, std::move(e), jreq.id));
+                    reply.push_back(JSONRPCReplyObj(NullUniValue, std::move(e), jreq.id, jreq.m_json_version));
                 } catch (const std::exception& e) {
-                    reply.push_back(JSONRPCReplyObj(NullUniValue, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq.id));
+                    reply.push_back(JSONRPCReplyObj(NullUniValue, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq.id, jreq.m_json_version));
                 }
             }
         }
@@ -243,10 +243,10 @@ static bool HTTPReq_JSONRPC(const std::any& context, HTTPRequest* req)
         req->WriteHeader("Content-Type", "application/json");
         req->WriteReply(HTTP_OK, reply.write() + "\n");
     } catch (UniValue& e) {
-        JSONErrorReply(req, std::move(e), jreq.id);
+        JSONErrorReply(req, std::move(e), jreq);
         return false;
     } catch (const std::exception& e) {
-        JSONErrorReply(req, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq.id);
+        JSONErrorReply(req, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq);
         return false;
     }
     return true;
diff --git a/src/rpc/request.cpp b/src/rpc/request.cpp
index 08e0658561..b5bf1e5ffa 100644
--- a/src/rpc/request.cpp
+++ b/src/rpc/request.cpp
@@ -37,14 +37,21 @@ UniValue JSONRPCRequestObj(const std::string& strMethod, const UniValue& params,
     return request;
 }
 
-UniValue JSONRPCReplyObj(UniValue result, UniValue error, UniValue id)
+UniValue JSONRPCReplyObj(UniValue result, UniValue error, UniValue id, JSONRPCVersion jsonrpc_version)
 {
     UniValue reply(UniValue::VOBJ);
-    if (!error.isNull())
-        reply.pushKV("result", NullUniValue);
-    else
+    // Add JSON-RPC version number field in v2 only.
+    if (jsonrpc_version == JSONRPCVersion::V2) reply.pushKV("jsonrpc", "2.0");
+
+    // Add both result and error fields in v1, even though one will be null.
+    // Omit the null field in v2.
+    if (error.isNull()) {
         reply.pushKV("result", std::move(result));
-    reply.pushKV("error", std::move(error));
+        if (jsonrpc_version == JSONRPCVersion::V1_LEGACY) reply.pushKV("error", NullUniValue);
+    } else {
+        if (jsonrpc_version == JSONRPCVersion::V1_LEGACY) reply.pushKV("result", NullUniValue);
+        reply.pushKV("error", std::move(error));
+    }
     reply.pushKV("id", std::move(id));
     return reply;
 }
diff --git a/src/rpc/request.h b/src/rpc/request.h
index 8b72172695..a7c9af2216 100644
--- a/src/rpc/request.h
+++ b/src/rpc/request.h
@@ -17,7 +17,7 @@ enum class JSONRPCVersion {
 };
 
 UniValue JSONRPCRequestObj(const std::string& strMethod, const UniValue& params, const UniValue& id);
-UniValue JSONRPCReplyObj(UniValue result, UniValue error, UniValue id);
+UniValue JSONRPCReplyObj(UniValue result, UniValue error, UniValue id, JSONRPCVersion jsonrpc_version);
 UniValue JSONRPCError(int code, const std::string& message);
 
 /** Generate a new RPC authentication cookie and write it to disk */
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index f199914095..8e150ef2b7 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -364,7 +364,7 @@ UniValue JSONRPCExec(const JSONRPCRequest& jreq)
     // but inside a batch, we just include the error object and return HTTP 200
     UniValue result = tableRPC.execute(jreq);
 
-    return JSONRPCReplyObj(std::move(result), NullUniValue, jreq.id);
+    return JSONRPCReplyObj(std::move(result), NullUniValue, jreq.id, jreq.m_json_version);
 }
 
 /**
diff --git a/test/functional/interface_rpc.py b/test/functional/interface_rpc.py
index 075dd1c2bc..dc9fb5d40f 100755
--- a/test/functional/interface_rpc.py
+++ b/test/functional/interface_rpc.py
@@ -48,7 +48,10 @@ def format_request(options, idx, fields):
 def format_response(options, idx, fields):
     response = {}
     response.update(id=None if options.notification else idx)
-    response.update(result=None, error=None)
+    if options.version == 2:
+        response.update(jsonrpc="2.0")
+    else:
+        response.update(result=None, error=None)
     response.update(fields)
     if options.response_fields:
         response.update(options.response_fields)