The problem was...
After a MaterialAsset reload, there could be two different versions of the MaterialAsset in memory: the old one and the reloaded one. The old one is still connected to buses and can send reinitialization messages when other things reload or reinitialize. So when the shader asset reloaded, both the old and new MaterialAsset were sending reinitialization messages. Material::OnMaterialAssetReinitialized was using the materialAsset parameter to initialize the Material, and the latest call to OnMaterialAssetReinitialized was for the *old* MaterialAsset.
The solution is to use the m_materialAsset member when reinitializing the Material. I also added checks in a couple places to skip unnecessary reinitialization, and added comments in the bus headers to warn developers about this issue.
Testing: Added a new step to ASV's MaterialHotReloadTest.bv.lua script for the error scenario, and this now passes. Ran ASV full test suite, both dx12 and vulkan, only known issues occurred.
This was done while working on "ATOM-15728 Shader Hot Reload Fails in Debug Build", but it turned out these changes did not actually fix the issue (or any other known hot-reload issue). Still, these improvements are appropriate as they correct logical oversights.
ShaderVariant was not listening to asset reloads. It needs to know when the ShaderVariantAsset reload happens so it can reinitialize it's members as well as propagate reinitialization messages. I added a member for the ShaderAsset as the class needs this to reinitialize itself. So now the class listens for reloads of both the ShaderVariantAsset and the ShaderAsset.
Shader was not listening for ShaderAsset reinitialization events.
Updated the API for ShaderReloadNotificationBus's OnShaderVariantReinitialized to include the ShaderVariant which is the most relevant information (the other information wasn't really being used anyway).
This is specifically in support of:
ATOM-14613 Baseviewer MatertialHotReloadTest fails to change the color after turning blending on and off
ATOM-15728 Shader Hot Reload Fails in Debug Build
Chris Santora
alexpete