Failure to build with no-fake-scoped-enums with emscripten

[slowriot]

When generating with fake scoped enums disabled, using the latest emscripten webgpu.h, I see multiple compilation errors from the WEBGPU_CPP_IMPLEMENTATION section of webgpu.h.

To generate:

python3 ./generate.py -u webgpu.h -t emscripten/webgpu.template.hpp -o webgpu.hpp -d defaults.txt -d extra-defaults.txt --no-fake-scoped-enums

When building, I get compilation errors such as:

webgpu.hpp:1341:16: fatal error: assigning to 'WGPUBackendType' from incompatible type 'wgpu::BackendType'
 1341 |         backendType = BackendType::Undefined;
      |                       ^~~~~~~~~~~~~~~~~~~~~~

These could be resolved with a change like backendType = static_cast<WGPUBackendType>(BackendType::Undefined).

[eliemichel]

Thanks for reporting this, I have to admit that I undertested this feature. Keeping this open until I fix and add automated tests! Thanks again for your multiple contributions!

[eliemichel]

Back at this, I realize that the issue you report is precisely why I had to use fake enums. So if you find a way to work it around properly, I would be happy to switch everything to real enums!

Looking at your commit history, I bet you wanted real enums to be able to use magic_enum, which is a fair need. You may always force the enum type when using magic_enum functions, e.g.:

ErrorType errorType = /* ... */;
std::cout << "Device error: " << magic_enum::enum_name<WGPUErrorType>(errorType);

But of course you will have the WGPUErrorType_ prefix in this case. Maybe a solution for you would be that the C++ wrapper also includes some enum to name conversion utilities? Ideally we should try and have this a compile-time thing so that it remains zero-overhead.

[slowriot]

Looking at your commit history, I bet you wanted real enums to be able to use magic_enum

Yes, you're exactly right. I ended up writing a small utility to cast the fake enum and then strip the leading WGPUErrorType_ etc, but it adds some runtime cost vs pure enum use, so I was hoping there could be a clean solution with normal enums. But aside from magic_enum, there are other use cases where passing around strongly typed enums is preferable from an ergonomic point of view (switch statements, etc).

I've also been working with the Dawn-derived CPP wrapper that comes with current versions of Emscripten, webgpu/webgpu_cpp.h, which I know you're familiar with. Its interface is more basic, and closer to the C API, often passing raw pointers, but it has the advantage that it provides human-readable strongly typed enums, that are still easily convertible to and from the C types. Maybe it's worth duplicating their approach to enums?