penrose VS hs-foreign-emscripten

There is a fork that compiles to js https://github.com/ghcjs/ghcjs compiler, and I believe the official glasgow compiler is working towards also supporting js/wasm (although I don't think they are supported as of yet).

I don't know anything about Haste, but you can get GHCJS 8.6 (or 8.10 with a bloated executable) via nix fairly easily or alternatively wait until the JS target recently merged into mainline ghc gets production ready: https://engineering.iog.io/2023-01-26-ghc-update.

Ah GHCJS does have this header: https://github.com/ghcjs/ghcjs/blob/ghc-8.10/lib/boot/data/include/stg/DLL.h

It seems like https://github.com/ghcjs/ghcjs/issues/821 is a rigid dealbreaker for any sizable project.

About the FFI: GHCJS extended the FFI to support inlined JS, named arguments, etc. See https://github.com/ghcjs/ghcjs/blob/master/doc/foreign-function-interface.md For now the JS backend only implements FFI calls similarly to native FFI. The rest will be open to discussion later (e.g. in a ghc-proposal) and should take into account the Wasm backend so that the same user code compiles with both backends as much as possible.

Other than that, I ran into a GHCJS and Miso bug, but they weren't too hard to solve.

There are a bunch of open branches. And yes, there is ghcjs support in haskell.nix, see this comment.

When I compile the ghc-8.8 branch locally, I get a number of test failures from the test suite. I'm not sure exactly how to fix them and they aren't currently my highest hobby priority.

ghcjs does support C FFI, and I know of this very rough prototype that helps with the gap between ghcjs C FFI expectations and emscripten output

i looked into that recently, and i found that GHCJS did compile the foreign import ccall into something but not quite emscripten-compatible. Another tool handled that though.