resolve compatibility with old ctor

include/sharg/parser.hpp

@@ -681,8 +681,9 @@ class parser
      */
     parser_meta_data info;
 
-    /*!\brief Adds subcommands to the parser.
-     * \param[in] subcommands A list of subcommands.
+    /*!\brief Adds a subcommand to the parser.
+     * \param[in] subcommand The subcommand to add.
+     * \returns A pointer to the sub-parser if subcommand is encountered, nullptr otherwise.
      * \throws sharg::design_error if the subcommand name contains illegal characters.
      */
     [[nodiscard]] parser * add_subcommand(std::string subcommand)
@@ -701,15 +702,19 @@ class parser
         };
 
         auto & parser_subcommands = this->subcommands;
-        parser_subcommands.emplace_back(std::move(subcommand));
+        parser_subcommands.emplace_back(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();
+        // If a subcommand was already added via the constructor, we need to check if the subcommand is the same.
+        if (sub_parser && sub_parser->info.app_name == info.app_name + '-' + subcommand)
+            return sub_parser.get();
+        else
+            return nullptr;
     }
 
 private:

test/snippet/readme_sneak_peek.cpp

@@ -2,8 +2,8 @@
 
 int main(int argc, char ** argv)
 {
-    // sharg::parser git_parser{"git", argc, argv, sharg::update_notifications::on, {"pull", "push", "remote"}}; // NOT ALLOWED
-    sharg::parser git_parser{"git", argc, argv, sharg::update_notifications::on};
+    //                                                                           -------- Optional --------
+    sharg::parser git_parser{"git", argc, argv, sharg::update_notifications::on, {"pull", "push", "remote"}};
 
     if (auto pull_parser = git_parser.add_subcommand("pull"))
     {

test/unit/parser/parser_design_error_test.cpp

@@ -263,7 +263,7 @@ TEST(parse_test, subcommand_parser_error)
         EXPECT_NO_THROW(top_level_parser.parse());
         EXPECT_EQ(true, flag_value);
 
-        EXPECT_THROW(top_level_parser.get_sub_parser(), sharg::design_error);
+        EXPECT_THROW(std::ignore = top_level_parser.get_sub_parser(), sharg::design_error);
     }
 
     // subcommand key word must only contain alpha numeric characters