1 files changed, 26 insertions, 12 deletions

diff --git a/src/rpc/util.h b/src/rpc/util.h
index d34c9cfdbb..d895e99c7e 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -12,6 +12,8 @@
 #include <string>
 #include <vector>
 
+#include <boost/variant.hpp>
+
 class CKeyStore;
 class CPubKey;
 class CScript;
@@ -42,11 +44,28 @@ struct RPCArg {
         AMOUNT,        //!< Special type representing a floating point amount (can be either NUM or STR)
         STR_HEX,       //!< Special type that is a STR with only hex chars
     };
+
+    enum class Optional {
+        /** Required arg */
+        NO,
+        /**
+         * Optinal arg that is a named argument and has a default value of
+         * `null`. When possible, the default value should be specified.
+         */
+        OMITTED_NAMED_ARG,
+        /**
+         * Optional argument with default value omitted because they are
+         * implicitly clear. That is, elements in an array or object may not
+         * exist by default.
+         * When possible, the default value should be specified.
+         */
+        OMITTED,
+    };
+    using Fallback = boost::variant<Optional, /* default value for optional args */ std::string>;
     const std::string m_name; //!< The name of the arg (can be empty for inner args)
     const Type m_type;
     const std::vector<RPCArg> m_inner; //!< Only used for arrays or dicts
-    const bool m_optional;
-    const std::string m_default_value; //!< Only used for optional args
+    const Fallback m_fallback;
     const std::string m_description;
     const std::string m_oneline_description; //!< Should be empty unless it is supposed to override the auto-generated summary line
     const std::vector<std::string> m_type_str; //!< Should be empty unless it is supposed to override the auto-generated type strings. Vector length is either 0 or 2, m_type_str.at(0) will override the type of the value in a key-value pair, m_type_str.at(1) will override the type in the argument description.
@@ -54,15 +73,13 @@ struct RPCArg {
     RPCArg(
         const std::string& name,
         const Type& type,
-        const bool opt,
-        const std::string& default_val,
+        const Fallback& fallback,
         const std::string& description,
         const std::string& oneline_description = "",
         const std::vector<std::string>& type_str = {})
         : m_name{name},
           m_type{type},
-          m_optional{opt},
-          m_default_value{default_val},
+          m_fallback{fallback},
           m_description{description},
           m_oneline_description{oneline_description},
           m_type_str{type_str}
@@ -73,8 +90,7 @@ struct RPCArg {
     RPCArg(
         const std::string& name,
         const Type& type,
-        const bool opt,
-        const std::string& default_val,
+        const Fallback& fallback,
         const std::string& description,
         const std::vector<RPCArg>& inner,
         const std::string& oneline_description = "",
@@ -82,8 +98,7 @@ struct RPCArg {
         : m_name{name},
           m_type{type},
           m_inner{inner},
-          m_optional{opt},
-          m_default_value{default_val},
+          m_fallback{fallback},
           m_description{description},
           m_oneline_description{oneline_description},
           m_type_str{type_str}
@@ -104,9 +119,8 @@ struct RPCArg {
     /**
      * Return the description string, including the argument type and whether
      * the argument is required.
-     * implicitly_required is set for arguments in an array, which are neither optional nor required.
      */
-    std::string ToDescriptionString(bool implicitly_required = false) const;
+    std::string ToDescriptionString() const;
 };
 
 struct RPCResult {