doc: Properly report optional RPC args

Author: MarcoFalke

src/rpc/util.cpp

@@ -405,12 +405,12 @@ struct Sections {
                 left += push_name ? arg.ToStringObj(/*oneline=*/false) : arg.ToString(/*oneline=*/false);
             }
             left += ",";
-            PushSection({left, arg.ToDescriptionString()});
+            PushSection({left, arg.ToDescriptionString(/*is_named_arg=*/push_name)});
             break;
         }
         case RPCArg::Type::OBJ:
         case RPCArg::Type::OBJ_USER_KEYS: {
-            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString();
+            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString(/*is_named_arg=*/push_name);
             PushSection({indent + (push_name ? "\"" + arg.GetName() + "\": " : "") + "{", right});
             for (const auto& arg_inner : arg.m_inner) {
                 Push(arg_inner, current_indent + 2, OuterType::OBJ);
@@ -425,7 +425,7 @@ struct Sections {
             auto left = indent;
             left += push_name ? "\"" + arg.GetName() + "\": " : "";
             left += "[";
-            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString();
+            const auto right = is_top_level_arg ? "" : arg.ToDescriptionString(/*is_named_arg=*/push_name);
             PushSection({left, right});
             for (const auto& arg_inner : arg.m_inner) {
                 Push(arg_inner, current_indent + 2, OuterType::ARR);
@@ -628,7 +628,7 @@ std::string RPCHelpMan::ToString() const
         if (i == 0) ret += "\nArguments:\n";
 
         // Push named argument name and description
-        sections.m_sections.emplace_back(::ToString(i + 1) + ". " + arg.GetFirstName(), arg.ToDescriptionString());
+        sections.m_sections.emplace_back(::ToString(i + 1) + ". " + arg.GetFirstName(), arg.ToDescriptionString(/*is_named_arg=*/true));
         sections.m_max_pad = std::max(sections.m_max_pad, sections.m_sections.back().m_left.size());
 
         // Recursively push nested args
@@ -722,7 +722,7 @@ bool RPCArg::IsOptional() const
     }
 }
 
-std::string RPCArg::ToDescriptionString() const
+std::string RPCArg::ToDescriptionString(bool is_named_arg) const
 {
     std::string ret;
     ret += "(";
@@ -768,14 +768,12 @@ std::string RPCArg::ToDescriptionString() const
         ret += ", optional, default=" + std::get<RPCArg::Default>(m_fallback).write();
     } else {
         switch (std::get<RPCArg::Optional>(m_fallback)) {
+        case RPCArg::Optional::OMITTED_NAMED_ARG: // Deprecated alias for OMITTED, can be removed
         case RPCArg::Optional::OMITTED: {
+            if (is_named_arg) ret += ", optional"; // Default value is "null" in dicts. Otherwise,
             // nothing to do. Element is treated as if not present and has no default value
             break;
         }
-        case RPCArg::Optional::OMITTED_NAMED_ARG: {
-            ret += ", optional"; // Default value is "null"
-            break;
-        }
         case RPCArg::Optional::NO: {
             ret += ", required";
             break;

src/rpc/util.h

@@ -154,21 +154,24 @@ struct RPCArg {
         /** Required arg */
         NO,
         /**
+         * The arg is optional for one of two reasons:
+         *
          * Optional arg that is a named argument and has a default value of
-         * `null`. When possible, the default value should be specified.
-         */
-        OMITTED_NAMED_ARG,
-        /**
+         * `null`.
+         *
          * Optional argument with default value omitted because they are
-         * implicitly clear. That is, elements in an array or object may not
+         * implicitly clear. That is, elements in an array may not
          * exist by default.
          * When possible, the default value should be specified.
          */
         OMITTED,
+        OMITTED_NAMED_ARG, // Deprecated alias for OMITTED, can be removed
     };
+    /** Hint for default value */
     using DefaultHint = std::string;
+    /** Default constant value */
     using Default = UniValue;
-    using Fallback = std::variant<Optional, /* hint for default value */ DefaultHint, /* default constant value */ Default>;
+    using Fallback = std::variant<Optional, DefaultHint, Default>;
 
     const std::string m_names; //!< The name of the arg (can be empty for inner args, can contain multiple aliases separated by | for named request arguments)
     const Type m_type;
@@ -234,7 +237,7 @@ struct RPCArg {
      * Return the description string, including the argument type and whether
      * the argument is required.
      */
-    std::string ToDescriptionString() const;
+    std::string ToDescriptionString(bool is_named_arg) const;
 };
 
 struct RPCResult {