From 72394c1b967be64071eef00afebe9541d45dca24 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@scylladb.com>
Date: Thu, 22 Aug 2024 17:51:31 +0300
Subject: [PATCH] app-template: add ability to specify options_description to
 be used for --help

Hiding options from --help output is useful when deprecating options.

When using boost::program_options, the way to hide options from
display is to provide an alternative options_description object and print
that. So this patch adds a way to provide a help-specific
options_description.

While this entangles us even more with boost::program_options, I don't
see a simple alternative.
---
 include/seastar/core/app-template.hh |  3 +++
 src/core/app-template.cc             | 35 +++++++++++++++++++---------
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/include/seastar/core/app-template.hh b/include/seastar/core/app-template.hh
index 8c5a15c8c28..47aef9c0f43 100644
--- a/include/seastar/core/app-template.hh
+++ b/include/seastar/core/app-template.hh
@@ -129,6 +129,7 @@ private:
     std::shared_ptr<smp> _smp;
     seastar_options _opts;
     boost::program_options::options_description _app_opts;
+    boost::program_options::options_description* _app_visible_opts_for_help = nullptr;
     boost::program_options::options_description _seastar_opts;
     boost::program_options::options_description _opts_conf_file;
     boost::program_options::positional_options_description _pos_opts;
@@ -136,6 +137,7 @@ private:
     configuration_reader _conf_reader;
 
     configuration_reader get_default_configuration_reader();
+    void add_extra_options(boost::program_options::options_description& opts);
 public:
     struct positional_option {
         const char* name;
@@ -153,6 +155,7 @@ public:
     boost::program_options::options_description& get_options_description();
     boost::program_options::options_description& get_conf_file_options_description();
     boost::program_options::options_description_easy_init add_options();
+    void set_app_visible_options_for_help(boost::program_options::options_description* opts);
     void add_positional_options(std::initializer_list<positional_option> options);
     boost::program_options::variables_map& configuration();
     int run_deprecated(int ac, char ** av, std::function<void ()>&& func) noexcept;
diff --git a/src/core/app-template.cc b/src/core/app-template.cc
index af76bda3721..5dcba0058b2 100644
--- a/src/core/app-template.cc
+++ b/src/core/app-template.cc
@@ -85,16 +85,7 @@ app_template::app_template(app_template::seastar_options opts)
         if (!alien::internal::default_instance) {
             alien::internal::default_instance = _alien.get();
         }
-        _app_opts.add_options()
-                ("help,h", "show help message")
-                ;
-        _app_opts.add_options()
-                ("help-seastar", "show help message about seastar options")
-                ;
-        _app_opts.add_options()
-                ("help-loggers", "print a list of logger names and exit")
-                ;
-
+        add_extra_options(_app_opts);
         {
             program_options::options_description_building_visitor visitor;
             _opts.describe(visitor);
@@ -109,12 +100,33 @@ app_template::app_template(app_template::config cfg)
 {
 }
 
+void
+app_template::add_extra_options(boost::program_options::options_description& opts) {
+    opts.add_options()
+            ("help,h", "show help message")
+            ;
+    opts.add_options()
+            ("help-seastar", "show help message about seastar options")
+            ;
+    opts.add_options()
+            ("help-loggers", "print a list of logger names and exit")
+            ;
+}
+
 app_template::~app_template() = default;
 
 const app_template::seastar_options& app_template::options() const {
     return _opts;
 }
 
+void
+app_template::set_app_visible_options_for_help(boost::program_options::options_description* opts) {
+    _app_visible_opts_for_help = opts;
+    if (_app_visible_opts_for_help) {
+        add_extra_options(*_app_visible_opts_for_help);
+    }
+}
+
 app_template::configuration_reader app_template::get_default_configuration_reader() {
     return [this] (bpo::variables_map& configuration) {
         auto home = std::getenv("HOME");
@@ -211,7 +223,8 @@ app_template::run_deprecated(int ac, char ** av, std::function<void ()>&& func)
         if (!_opts.description.empty()) {
             std::cout << _opts.description << "\n";
         }
-        std::cout << _app_opts << "\n";
+        auto& which_opts = _app_visible_opts_for_help ? *_app_visible_opts_for_help : _app_opts;
+        std::cout << which_opts << "\n";
         return 0;
     }
     if (configuration.count("help-seastar")) {