alternative approach

include/sharg/parser.hpp

@@ -189,7 +189,11 @@ class parser
     {
         info.app_name = app_name;
 
-        add_subcommands(std::move(subcommands));
+        for (auto const & subcommand : subcommands)
+            std::ignore /* function is nodisard */ = add_subcommand(subcommand);
+
+        if (subcommands.empty())
+            init();
     }
 
     //!\overload
@@ -453,12 +457,18 @@ class parser
      * \details
      * \stableapi{Since version 1.0.}
      */
-    parser & get_sub_parser()
+    [[nodiscard]] parser & get_sub_parser()
     {
+        // Technically not, as sub_parser is set via init(), but if if no subcommand is used in the command line,
+        // we do not process special formats (help/short-help/etc.) for the top-level parser.
+        if (!parse_was_called)
+            throw design_error("The function parse() must be called before get_sub_parser!");
+
+        if (subcommands.empty())
+            throw design_error("No subcommand was provided for the argument parser!");
+
         if (sub_parser == nullptr)
-        {
-            throw design_error("No subcommand was provided at the construction of the argument parser!");
-        }
+            throw design_error("There is no subparser!");
 
         return *sub_parser;
     }
@@ -675,31 +685,31 @@ class parser
      * \param[in] subcommands A list of subcommands.
      * \throws sharg::design_error if the subcommand name contains illegal characters.
      */
-    void add_subcommands(std::vector<std::string> const & subcommands)
+    [[nodiscard]] parser * add_subcommand(std::string subcommand)
     {
-        check_parse_not_called("add_subcommands");
-        for (auto const & sub : subcommands)
+        check_parse_not_called("add_subcommand");
+
+        if (!std::regex_match(subcommand, app_name_regex))
         {
-            if (!std::regex_match(sub, app_name_regex))
-            {
-                std::string const error_message =
-                    detail::to_string(std::quoted(info.app_name),
-                                      " contains an invalid subcommand name: ",
-                                      std::quoted(sub),
-                                      ". The subcommand name must only contain alpha-numeric characters ",
-                                      "or '_' and '-' (regex: \"^[a-zA-Z0-9_-]+$\").");
-                throw design_error{error_message};
-            };
-        }
+            std::string const error_message =
+                detail::to_string(std::quoted(info.app_name),
+                                  " contains an invalid subcommand name: ",
+                                  std::quoted(subcommand),
+                                  ". The subcommand name must only contain alpha-numeric characters ",
+                                  "or '_' and '-' (regex: \"^[a-zA-Z0-9_-]+$\").");
+            throw design_error{error_message};
+        };
 
         auto & parser_subcommands = this->subcommands;
-        parser_subcommands.insert(parser_subcommands.end(), subcommands.cbegin(), subcommands.cend());
+        parser_subcommands.emplace_back(std::move(subcommand));
 
         std::ranges::sort(parser_subcommands);
         auto const [first, last] = std::ranges::unique(parser_subcommands);
         parser_subcommands.erase(first, last);
 
         init();
+
+        return sub_parser.get();
     }
 
 private: