Crash when loading a newly installed plugin

[dkondor]

Describe the bug
Wayfire crashes when trying to load a plugin that was installed after it had originally started. Might only happen for plugins that use keybinding, but haven't investigated in detail.

To Reproduce
Steps to reproduce the behavior:

1. Start Wayfire
2. Install a new plugin (tested with this plugin, but I expect the same behavior with others)
3. Enable it (WCM or config file)
4. Wayfire crashes

Expected behavior
No crash. Ideally, the new plugin should be able to load, but it is acceptable to required restarting Wayfire as long as it does not crash.

Screenshots or stacktrace
If applicable, add screenshots to help explain your problem.
If it is a crash, attach the backtrace (or the whole log file), Wayfire will print it in the end of the log file or stdout.
Backtrace with address sanitizer enabled (if possible):

EE 12-01-25 15:24:52.738 - [src/debug.cpp:401] Wayfire encountered error loading option "screenlock_integration/lock": No such option: screenlock_integration/lock. Usual reasons for this include missing or outdated plugin XML files, a bug in the plugin itself, or mismatch between the versions of Wayfire and wf-config. Make sure that you have the correct versions of all relevant packages and make sure that there are no conflicting installations of Wayfire using the same prefix.
EE 12-01-25 15:24:52.867 - #1  wf::detail::option_wrapper_debug_message(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::runtime_error const&) ../src/debug.cpp:407
EE 12-01-25 15:24:53.557 - #2  wf::option_wrapper_t<wf::keybinding_t>::load_option(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ../src/api/wayfire/option-wrapper.hpp:41 (discriminator 1)
EE 12-01-25 15:24:54.082 - #3  wf::option_wrapper_t<wf::keybinding_t>::option_wrapper_t(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ../src/api/wayfire/option-wrapper.hpp:32
EE 12-01-25 15:24:54.107 - #4  screenlock_integration::init() ../wayfire_plugin/screenlock_integration.cpp:47 (discriminator 4)
EE 12-01-25 15:24:54.324 - #5  wf::plugin_manager_t::reload_dynamic_plugins() ../src/core/plugin-loader.cpp:228
EE 12-01-25 15:24:54.559 - #6  wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}::operator()() const ../src/core/plugin-loader.cpp:23
EE 12-01-25 15:24:54.774 - #7  void std::__invoke_impl<void, wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}&>(std::__invoke_other, wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}&) /usr/include/c++/13/bits/invoke.h:61
EE 12-01-25 15:24:55.092 - #8  std::enable_if<is_invocable_r_v<void, wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}&>, void>::type std::__invoke_r<void, wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}&>(wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}&) /usr/include/c++/13/bits/invoke.h:117
EE 12-01-25 15:24:55.473 - #9  std::_Function_handler<void (), wf::plugin_manager_t::plugin_manager_t()::{lambda()#1}::operator()() const::{lambda()#1}>::_M_invoke(std::_Any_data const&) /usr/include/c++/13/bits/std_function.h:291
EE 12-01-25 15:24:55.625 - #10 std::function<void ()>::operator()() const ../src/util.cpp:591
EE 12-01-25 15:24:55.748 - #11 wf::wl_idle_call::execute() ../src/util.cpp:91
EE 12-01-25 15:24:55.845 - #12 handle_idle_listener(void*) ../src/util.cpp:27
EE 12-01-25 15:24:55.858 - #13 wl_event_loop_dispatch_idle ??:?
EE 12-01-25 15:24:55.870 - #14 wl_event_loop_dispatch ??:?
EE 12-01-25 15:24:55.884 - #15 wl_display_run ??:?
EE 12-01-25 15:24:55.968 - #16 main ../src/main.cpp:456
EE 12-01-25 15:24:56.154 - #17 __libc_start_call_main ../sysdeps/x86/libc-start.c:74
EE 12-01-25 15:24:56.375 - #18 call_init ../csu/libc-start.c:128
EE 12-01-25 15:24:58.836 - #19 _start ??:?

Wayfire version
git (actually this branch, but I don't expect any difference to master)
0.8.0+git20240110-2.1build1 (the version in Ubuntu 24.04)

Additional info

The problem seems to come from wf-config, which does not update its internal state when the new plugin is installed. Specifically, loading the plugin tries to read its config (screenlock_integration/lock in the above case), ending up here. The get_section() function then returns nullptr, since I assume there is no mechanism to look for xml files that were added since Wayfire was started.

This is turn results in throwing an exception from here

This is caught here and the error message is printed followed by the stacktrace.

Possible solutions

1. Improve wf-config to dynamically rescan the metadata directory when it changes (or at least when a section is not found). This would be a complete solution, allowing to load freshly installed plugins, but seems complicated and can lead to weird edge cases.
2. Refuse to load plugins whose metadata is not loaded. This required restarting Wayfire after installing a plugin, which is still reasonable, and probably less error-prone. However, it needs some extra communication between the config backend and the plugin loader.