Best practices for optional feature enablement

[eddiehatfield]

tldr

I'm not sure how to conditionally enable VkPhysicalDeviceVulkan12Features::timelineSemaphore when using a vulkan profile that already customizes VkPhysicalDeviceVulkan12Features in the pNext chain.

Background

I am writing a simple Vulkan application that uses a bindless rendering model. I am using the vulkan_profiles.hpp library as follows:
I have a custom profile called baseline.json, which I use to generate a vulkan_profiles.hpp file from this profile using a python script shipped with my Vulkan SDK. This profile contains the features that are absolutely required for my engine to run, which currently includes VK_KHR_swapchain, VK_KHR_dynamic_rendering, VK_KHR_draw_indirect_count, and VK_EXT_descriptor_indexing. Within the features JSON object, I have enabled VkPhysicalDeviceVulkan12Features::{drawIndirectCount,descriptorIndexing,runtimeDescriptorArray}. Without these features, my engine won't work at all.

In some of my rendering codepaths, I check via if-statement whether timeline semaphores are supported, in which case I make use of them. If this feature isn't supported, then the engine will still work.

Issue

My current issue is that I am unsure how to enable VkPhysicalDeviceVulkan12Features::timelineSemaphore, since I create my VkDevice via vpCreateDevice with the profile generated from baseline.json. I don't see a way to set the timelineSemaphore field to true since the pNext chain is completely handled by this function. Do I need to create a separate profile only for checking timelineSemaphore, then append that to pEnabledFullProfiles if it is supported?

Please let me know if I am not following the desired usage of this library.