Hi, glad to hear it's useful :)

Thank you for attaching the project. I'm not an expert in how different modules are resolved in different bundlers (it's a mess), but I'll give it a look.

@ostryhub It seems the source of the issue is that Javascript "glue" code generated by Emscripten messes up with Webpack mechanisms, see webpack/webpack#7352.

I've tried building the library with -s ENVIRONMENT=web, which fixed the issue.
(also it was necessary to add "moduleResolution": "Node" to the compilerOptions in your project's tsconfig.json)

The problem is that I cannot use this build config since that would break node compatibility (which at least the library tests require). I suggest either changing your bundler to e.g. Vite, or try some of the suggestions in the mentioned issue. Alternatively, you may create a separate fork of this library with the altered build config, the change is in planegcs/CMakeLists.txt, line 51:
set_target_properties(planegcs PROPERTIES LINK_FLAGS "${BUILD_TYPE_FLAGS} -lembind --closure 1 -s EXPORT_ES6=1 -s MODULARIZE=1 -s MALLOC=emmalloc -s NO_FILESYSTEM=1 -s STACK_SIZE=5MB -s ENVIRONMENT=web")

I might also investigate if there is a way to include multiple different wasm builds into the library. That could also fix your problem.

@thes01 Thank you for such a quick answer and looking into the problem.
The idea of building web targeting emsc build does sound like a way to go for me.
I will give it a try after the weekend and share the results here.

Regarding the multi wasm build, I am unabe to help unfortunately, but maybe checking this great occt wasm port https://github.com/donalffons/opencascade.js/ could shed some more light on the possible configuration.

Yes, no problem :).

In OpenCascade.js, it seems that they ship just one build with the possibility of customization. (But anyway, there is a pretty nice process of the build configuration, which I might apply to planegcs as well)

I think it could be possible to just include multiple .wasm builds in the library (at least one for the browser-only). And then by using the locateFile argument, you could choose, which wasm variant to load.
const mod = await init_planegcs_module({ locateFile: () => wasm_url });

The web build did work when packaged into UMD module with webpack.
The CMakeLists.txt change I used in the end is this:

set_target_properties(planegcs PROPERTIES LINK_FLAGS "${BUILD_TYPE_FLAGS} -lembind --closure 1 -s SINGLE_FILE=1 -s EXPORT_ES6=1 -s USE_ES6_IMPORT_META=0 -s MODULARIZE=1 -s MALLOC=emmalloc -s NO_FILESYSTEM=1 -s STACK_SIZE=5MB -s ENVIRONMENT=web")

I am loading this UMD module into a vanialla v8 JS runtime and what also helped me a lot is this single file option that emdeds the wasm file as base64 encoded string into the js module loading file

-s SINGLE_FILE=1

Vanilla v8 doesn't have Base64 atob decoder needed for embedded wasm loading, so one last thing one needs is to include the Base64 js library and expose it as global atob variable, like so:

import {encode, decode} from "base-64"
const globalScope: any = window || process || global;
globalScope.atob = decode;
globalScope.btoa = encode;

Thank you @thes01 for the help and this wrapper again!