Combined capability flags are limiting

[zakarumych]

I have a shader that need to do non-uniform indexing into array of sampled images.
Vulkan extension supports non-uniform indexing into image arrays (both sampled and storage) and does not support non-uniform indexing of buffer arrays.

Naga has this capability flag - SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING
For some reason sampled texture and storage buffer arrays non-uniform indexing live under one flag.
And UNIFORM_BUFFER_AND_STORAGE_TEXTURE_ARRAY_NON_UNIFORM_INDEXING combines uniform buffer and storage texture arrays indexing.
This looks especially weird since flags combine different opposite kinds of buffer and texture arrays.

Due to those peculiar combinations I can't enable either of the flags on my machine.
In turn I can't validate my wgsl shader without dirty hacks.

[cwfitzgerald]

To answer why the flags are combined, we couldn't find any machines during our initial investigation where they had one of the flag but not another. Do you have a machine with a feature partly supported? If so which machine (got a vulkan.gpuinfo report?)

[cwfitzgerald]

Moved to wgpu because Naga just follows wgpu here.

[zakarumych]

Here's vulkaninfo output
As you can guess. It's actually Metal wrapped in MoltenVK.

[cwfitzgerald]

I'm not sure if we really should accommodate MoltenVK considering the metal backend now supports descriptor indexing natively.

[zakarumych]

Some software works with Vulkan API and for now MoltenVK is the only maintained project that emulates Vulkan on Apple OSes.
Do you suggest not using naga in this case?

[cwfitzgerald]

Is your use case using Naga for a non-wgpu application? It's definitely worthwhile to split it in Naga then, splitting it in wgpu is a bit of a bigger question, but this has come up before that whatever flags we use, some of them are wrong

[zakarumych]

Yes, I use naga as shader compiler for my Vulkan based graphics API, to accept shaders in whatever language and transform them to spir-V.

[teoxoy]

Moved this back to naga, will be addressed once we get to gfx-rs/wgpu#4407. PRs are also welcome :)