RPC: Add add OBJ_NAMED_PARAMS type

OBJ_NAMED_PARAMS type works the same as OBJ type except it registers the object
keys to be accepted as top-level named-only RPC parameters. Generated
documentation also lists the object keys seperately in a new "Named arguments"
section of help text.

Named-only RPC parameters have the same semantics as python keyword-only
arguments (https://peps.python.org/pep-3102/). They are always required to be
passed by name, so they don't affect interpretation of positional arguments,
and aren't affected when positional arguments are added or removed.

The new OBJ_NAMED_PARAMS type is used in the next commit to make it easier to
pass options values to various RPC methods.

Co-authored-by: Andrew Chow <github@achow101.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/src/rpc/server.h b/src/rpc/server.h
index 01e8556050..24658ddb8b 100644
--- a/src/rpc/server.h
+++ b/src/rpc/server.h
@@ -95,7 +95,7 @@ public:
     using Actor = std::function<bool(const JSONRPCRequest& request, UniValue& result, bool last_handler)>;
 
     //! Constructor taking Actor callback supporting multiple handlers.
-    CRPCCommand(std::string category, std::string name, Actor actor, std::vector<std::string> args, intptr_t unique_id)
+    CRPCCommand(std::string category, std::string name, Actor actor, std::vector<std::pair<std::string, bool>> args, intptr_t unique_id)
         : category(std::move(category)), name(std::move(name)), actor(std::move(actor)), argNames(std::move(args)),
           unique_id(unique_id)
     {
@@ -115,7 +115,16 @@ public:
     std::string category;
     std::string name;
     Actor actor;
-    std::vector<std::string> argNames;
+    //! List of method arguments and whether they are named-only. Incoming RPC
+    //! requests contain a "params" field that can either be an array containing
+    //! unnamed arguments or an object containing named arguments. The
+    //! "argNames" vector is used in the latter case to transform the params
+    //! object into an array. Each argument in "argNames" gets mapped to a
+    //! unique position in the array, based on the order it is listed, unless
+    //! the argument is a named-only argument with argNames[x].second set to
+    //! true. Named-only arguments are combined into a JSON object that is
+    //! appended after other arguments, see transformNamedArguments for details.
+    std::vector<std::pair<std::string, bool>> argNames;
     intptr_t unique_id;
 };