[SpecializationConstants] We should probably allow unbound shader resources when spec constants enabled, or adding sth. like `PIPELINE_RESOURCE_FLAG_ALLOW_UNBOUND` ?

[hzqst]

otherwise we will have to bind an empty resource to every ShaderResourceVariable even it is not used at all.

   [SpecializationConstant] const int BaseTextureEnabled = 0;

    if (BaseTextureEnabled != 0)
    {
        baseColor = g_BaseTexture.Sample(g_BaseTexture_sampler, baseTexcoord);
    }

we know that g_BaseTexture will never be used in this case unless BaseTextureEnabled explicitly set in PSOCreate.pSpecializationConstant.

Currently, I'm using pShaderVariables->Set(m_pEmptyShaderVariableResource); to mitigate the issue, where m_pEmptyShaderVariableResource is a 1x1 Texture2D. not a good option though.

[TheMostDiligent]

What happens if you disable the check?
Do Vulkan validation layers allow null resources in this case?
Also, what happens in WebGPU? I would be really surprised if it does not error out with null resource in this scenario.