get_subcommand_no_throw (#1016)

get_subcommand when used for parsing config files, was throwing and
catching as part of control flow and expected operation, this resulting
in a performance hit in select cases. A get_subcommand_no_throw was
added to resolve this issue.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/CLI/App.hpp

@@ -733,6 +733,10 @@ class App {
     /// Check to see if a subcommand is part of this command (text version)
     CLI11_NODISCARD App *get_subcommand(std::string subcom) const;
 
+    /// Get a subcommand by name (noexcept non-const version)
+    /// returns null if subcommand doesn't exist
+    CLI11_NODISCARD App *get_subcommand_no_throw(std::string subcom) const noexcept;
+
     /// Get a pointer to subcommand by index
     CLI11_NODISCARD App *get_subcommand(int index = 0) const;
 
@@ -907,8 +911,9 @@ class App {
     }
 
     /// Check with name instead of pointer to see if subcommand was selected
-    CLI11_NODISCARD bool got_subcommand(std::string subcommand_name) const {
-        return get_subcommand(subcommand_name)->parsed_ > 0;
+    CLI11_NODISCARD bool got_subcommand(std::string subcommand_name) const noexcept {
+        App *sub = get_subcommand_no_throw(subcommand_name);
+        return (sub != nullptr) ? (sub->parsed_ > 0) : false;
     }
 
     /// Sets excluded options for the subcommand
@@ -1038,7 +1043,7 @@ class App {
     std::vector<Option *> get_options(const std::function<bool(Option *)> filter = {});
 
     /// Get an option by name (noexcept non-const version)
-    Option *get_option_no_throw(std::string option_name) noexcept;
+    CLI11_NODISCARD Option *get_option_no_throw(std::string option_name) noexcept;
 
     /// Get an option by name (noexcept const version)
     CLI11_NODISCARD const Option *get_option_no_throw(std::string option_name) const noexcept;

include/CLI/impl/App_inl.hpp

@@ -457,6 +457,10 @@ CLI11_NODISCARD CLI11_INLINE App *App::get_subcommand(std::string subcom) const
     return subc;
 }
 
+CLI11_NODISCARD CLI11_INLINE App *App::get_subcommand_no_throw(std::string subcom) const noexcept {
+    return _find_subcommand(subcom, false, false);
+}
+
 CLI11_NODISCARD CLI11_INLINE App *App::get_subcommand(int index) const {
     if(index >= 0) {
         auto uindex = static_cast<unsigned>(index);
@@ -796,7 +800,7 @@ CLI11_INLINE std::vector<Option *> App::get_options(const std::function<bool(Opt
     return options;
 }
 
-CLI11_INLINE Option *App::get_option_no_throw(std::string option_name) noexcept {
+CLI11_NODISCARD CLI11_INLINE Option *App::get_option_no_throw(std::string option_name) noexcept {
     for(Option_p &opt : options_) {
         if(opt->check_name(option_name)) {
             return opt.get();
@@ -1441,12 +1445,8 @@ CLI11_INLINE void App::_parse_config(const std::vector<ConfigItem> &args) {
 CLI11_INLINE bool App::_parse_single_config(const ConfigItem &item, std::size_t level) {
 
     if(level < item.parents.size()) {
-        try {
-            auto *subcom = get_subcommand(item.parents.at(level));
-            return subcom->_parse_single_config(item, level + 1);
-        } catch(const OptionNotFound &) {
-            return false;
-        }
+        auto *subcom = get_subcommand_no_throw(item.parents.at(level));
+        return (subcom != nullptr) ? subcom->_parse_single_config(item, level + 1) : false;
     }
     // check for section open
     if(item.name == "++") {

tests/SubcommandTest.cpp

@@ -16,8 +16,10 @@ TEST_CASE_METHOD(TApp, "BasicSubcommands", "[subcom]") {
 
     CHECK(app.get_subcommand(sub1) == sub1);
     CHECK(app.get_subcommand("sub1") == sub1);
+    CHECK(app.get_subcommand_no_throw("sub1") == sub1);
     CHECK_THROWS_AS(app.get_subcommand("sub3"), CLI::OptionNotFound);
-
+    CHECK_NOTHROW(app.get_subcommand_no_throw("sub3"));
+    CHECK(app.get_subcommand_no_throw("sub3") == nullptr);
     run();
     CHECK(app.get_subcommands().empty());
 
@@ -90,7 +92,7 @@ TEST_CASE_METHOD(TApp, "MultiSubFallthrough", "[subcom]") {
     CHECK(!sub2->parsed());
     CHECK(0u == sub2->count());
 
-    CHECK_THROWS_AS(app.got_subcommand("sub3"), CLI::OptionNotFound);
+    CHECK(!app.got_subcommand("sub3"));
 }
 
 TEST_CASE_METHOD(TApp, "CrazyNameSubcommand", "[subcom]") {