BsfImportTool depends on pre-built assets, crashes without them

[nemerle]

I've encountered this problem when working on the VertexDataDecl PR, when the VertexDataDecl was used in some places that caused the serialized structure layout to change in GpuProgramBytecode. I can force it to work by reverting a few changes around there, but I think that this problem can make any future changes to serialized shader asset layout quite painful? Below is the analysis of the issue:

The import tool cannot be started if the compiled shader assets are missing. Even if we want to create compiled shader assets 😄

This is caused by the following reduced chain of calls:

• Running bsfImportTool on "IrradianceComputeSH.bsl" executes:
• Application::startUp which calls
• RenderBeast::initializeCore which calls
• RenderBeastIBLUtility::filterCubemapForIrradiance which requires that BuiltinResources::getShader returned a proper shader for "IrradianceComputeSH.bsl"
• and that requires the asset to already exist.

This looks very much like a bootstrap problem encountered when a compiler is written in a language it's meant to compile.

[BearishSun]

Yeah I've encountered this myself last week. The proper solution would be to get the import tool to compile with null renderer and render backend. If that's not enough, then add checks in these sort of places, so they can handle the case when the builtin assets are missing (or an #if with a separate code path for the import tool).

It's something I'll get around to, but for now not a high priority unless its blocking someone.

[nemerle]

Simply replacing it with null renderer and backend fails around here

#2  [addr] in bs::Module<bs::ct::RenderAPI>::instance () at bsfUtility/Utility/BsModule.h:30
#3  [addr] in bs::ct::GUISpriteParamBlockDef::initialize (this=0x7ffff7fc5dc0 <bs::ct::gGUISpriteParamBlockDef>) at bsfEngine/GUI/BsGUIManager.h:445
#4  [addr] in bs::ct::ParamBlockManager::ParamBlockManager (this=0x51c2a0) at bsfCore/Renderer/BsParamBlocks.cpp:18
#5  [addr] in bs::bs_new<bs::ct::ParamBlockManager> () at bsfUtility/Allocators/BsMemoryAllocator.h:354
#6  [addr] in bs::Module<bs::ct::ParamBlockManager>::startUp<>() () at bsfUtility/Utility/BsModule.h:71
#7  [addr] in bs::CoreApplication::onStartUp (this=0x4c8aa0) at bsfCore/BsCoreApplication.cpp:173
#8  [addr] in bs::Application::onStartUp (this=0x4c8aa0) at bsfEngine/BsApplication.cpp:52
#9  [addr] in bs::Module<bs::CoreApplication>::startUp<bs::Application, bs::START_UP_DESC const&> (args#0=...) at bsfUtility/Utility/BsModule.h:92
#10 [addr] in bs::Application::startUp<bs::Application> (desc=...) at bsfEngine/BsApplication.h:40
#11 [addr] in main (argc=4, argv=0x7fffffffe458) at bsfEngine/Resources/BsBuiltinResourcesImporter.cpp:60