1 files changed, 27 insertions, 1 deletions
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index 1d7bd2eb94..f57133f75b 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -401,8 +401,16 @@ static inline JSONRPCRequest transformNamedArguments(const JSONRPCRequest& in, c
     for (size_t i=0; i<keys.size(); ++i) {
         argsIn[keys[i]] = &values[i];
     }
-    // Process expected parameters.
+    // Process expected parameters. If any parameters were left unspecified in
+    // the request before a parameter that was specified, null values need to be
+    // inserted at the unspecifed parameter positions, and the "hole" variable
+    // below tracks the number of null values that need to be inserted.
+    // The "initial_hole_size" variable stores the size of the initial hole,
+    // i.e. how many initial positional arguments were left unspecified. This is
+    // used after the for-loop to add initial positional arguments from the
+    // "args" parameter, if present.
     int hole = 0;
+    int initial_hole_size = 0;
     for (const std::string &argNamePattern: argNames) {
         std::vector<std::string> vargNames = SplitString(argNamePattern, '|');
         auto fr = argsIn.end();
@@ -424,6 +432,24 @@ static inline JSONRPCRequest transformNamedArguments(const JSONRPCRequest& in, c
             argsIn.erase(fr);
         } else {
             hole += 1;
+            if (out.params.empty()) initial_hole_size = hole;
+        }
+    }
+    // If leftover "args" param was found, use it as a source of positional
+    // arguments and add named arguments after. This is a convenience for
+    // clients that want to pass a combination of named and positional
+    // arguments as described in doc/JSON-RPC-interface.md#parameter-passing
+    auto positional_args{argsIn.extract("args")};
+    if (positional_args && positional_args.mapped()->isArray()) {
+        const bool has_named_arguments{initial_hole_size < (int)argNames.size()};
+        if (initial_hole_size < (int)positional_args.mapped()->size() && has_named_arguments) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Parameter " + argNames[initial_hole_size] + " specified twice both as positional and named argument");
+        }
+        // Assign positional_args to out.params and append named_args after.
+        UniValue named_args{std::move(out.params)};
+        out.params = *positional_args.mapped();
+        for (size_t i{out.params.size()}; i < named_args.size(); ++i) {
+            out.params.push_back(named_args[i]);
         }
     }
     // If there are still arguments in the argsIn map, this is an error.