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README.md

Ormolu Live

Play around with Ormolu in the browser via the GHC WASM backend!

https://ormolu-live.tweag.io

Overview

ATM, the GHC WASM backend only supports emitting WASI binaries, which can be run in the browser via e.g. browser_wasi_shim or the more fully-featured wasmer-wasi.

Hence, Ormolu Live consists of two parts:

  • A regular Purescript frontend (in src/) that displays input/output and manages options.
  • A background web worker (in this directory with the source in app/Main.hs) that formats Haskell source code via the WASM-compiled Ormolu.

Development

Make sure to be in the .#ormoluLive Nix shell when entering ./ormolu-live, e.g. conveniently via nix-direnv.

Local interactive development

For building the WASM binary, run

wasm32-wasi-cabal update

and then iterate by running something like

watchexec -w app ./build-wasm.sh

For the Purescript frontend, you can run

watchexec -w src purs-nix compile

and

parcel www/index.html

in parallel. The latter command will display the URL to a dev server, usually http://localhost:1234.

Building the site for deployment

First, build the components:

nix build .#ormoluLive
wasm32-wasi-cabal update
./build-wasm.sh -Oz

Here, -Oz tells wasm-opt to aggressively optimize for code size.

Then, combine the two:

cp -r --no-preserve=mode,ownership result/ site
cp src/ormolu.wasm site/ormolu.*.wasm

The self-contained site is now in site.

Acknowledgements

https://github.com/monadfix/ormolu-live