Godot 3.6: Cannot build Web export template with Mono enabled

[dtsioni]

Tested versions

Branch 3.6

System information

Windows 10 - WSL (Ubuntu) - Godot 3.6.1 - Mono - WASM - Javascript/Web

Issue description

I'm working in branch 3.6. I want to build a custom export template for the Web platform with the module Mono enabled. I have been trying to get this to work for a few weeks already and I cannot get one export template building correctly. I'm building everything inside of WSL and I've been trying to follow all documentation to a T.

As per https://docs.godotengine.org/en/3.6/development/compiling/compiling_with_mono.html
I've built the glue using the Windows platform exe. I also tried the glue generated with the x11 platform bin.

As per https://github.com/godotengine/godot-mono-builds
I've built the wasm runtime.

As per https://docs.godotengine.org/en/3.6/development/compiling/compiling_for_web.html
I've run scons platform=javascript tools=no target=release module_mono_enabled=yes mono_glue=yes extra_suffix=js-mono-1 mono_prefix=$HOME/mono-installs/wasm-runtime-release

Everything compiles, until I get the following error:
[ 66%] Linking Program ==> bin/godot.javascript.opt.js-mono-1.mono.js
error: undefined symbol: godot_mono_register_m2n_icall_trampoline_dispatch_hook

Google returns no results for this error.

Am I doing something wrong, is this not supported, or is there an issue with the engine itself?

The default export template for Godot 3.6 Mono HTML5 works, so I have to assume that it's possible to build a custom one as well. However, nothing is working according to the official documentation.

Steps to reproduce

Pull down Godot 3.6 in WSL.
Build windows exe with mono enabled.
Generate mono glue.
Pull down godot-mono-builds and build the wasm runtime.
Run scons platform=javascript tools=no target=release module_mono_enabled=yes mono_glue=yes extra_suffix=js-mono-1 mono_prefix=$HOME/mono-installs/wasm-runtime-release

Minimal reproduction project (MRP)

The project is no different than what is present on the 3.6 branch. The issue is likely environmental.

[akien-mga]

Your build of the wasm-runtime from godot-mono-builds seems to be lacking this patch:
https://github.com/godotengine/godot-mono-builds/blob/master/files/patches/wasm_m2n_trampolines_hook.diff

You need to run both patch_mono.py and patch_emscripten.py before building the runtime with godot-mono-builds' scripts.

You can also download our prebuilt runtimes:
https://github.com/godotengine/godot-mono-builds/releases/tag/release-4912f62

[dtsioni]

Thank you.

The project builds with the prebuilt runtime, but the exported build does not actually run on the web. The browser outputs the following error:

ERROR: Cannot instance script because the project assembly is not loaded. Script: 'res://Main.cs'. > index.js:369
at: can_instance (modules/mono/csharp_script.cpp:2888) - Method failed. Returning: 0L > index.js:369

I don't understand, is this supported or not? Getting this to work has been more than an uphill battle, and the documentation here is severely lacking.

[dtsioni]

For example, ./patch_mono.py does not work on the latest mono/mono source code commit, only on some undetermined prior commit. Similarly IIRC I had to rewind emsdk as well for ./patch_emscripten.py to work.

The prebuilt runtime seems to work in regards to those issues however, so thank you for that. But nothing in the documentation gives any clue what to do regarding this project assembly issue.

[akien-mga]

Yeah it's not very well documented, because it's quite complex, and not relevant anymore for Godot 4 which is the main development focus. The best way to get a working setup is to replicate ours (using podman on Fedora):

• https://github.com/godotengine/build-containers/tree/3.x
• https://github.com/godotengine/godot-build-scripts/tree/3.x

Notably for Godot 3.6, the tested/supported toolchains for Mono are Mono 6.12.0.198 (but latest stable 6.12.0.206 may also work) and Emscripten 1.39.9: https://github.com/godotengine/build-containers/tree/3.x?tab=readme-ov-file#toolchains

[dtsioni]

That worked, thank you! That should be in the official documentation, it's a much easier process than getting the build environment set up locally.

[dtsioni]

Only caveat was that the $IMAGE_VERSION in the godot-build-scripts/build.sh file was not being set properly when I ran it, and I had to override it with what podman images was outputting as the image tag. Not sure if that was my fault or what, but it was easy enough to fix.