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Rust & WebAssembly

tldr; The future of Rust webapps is bright; the present is rocky.

My latest side project uses CRDTs to merge changes from multiple clients, while also allowing offline edits & immediate local feedback. The Automerge CRDT library is written in Rust, so I have been learning the ins & outs of working with WebAssembly in the browser.

Bundlers

I’m told that Webpack can be configured to import webassembly files, or JS files that transitively import webassembly, with the same syntax as normal ES6 imports. Unfortunately, I still don’t have the patience to learn to configure Webpack, and I will go to great lengths to avoid it. For last year’s CRDT project that meant using Parcel, which worked great until I tried to import WebAssembly. Alas, Parcel does not support wasm today (Parcel v1 apparently did, and Automerge v0.1 was pure JS, which is how tack works, but for today I want to use the actively developed versions.)

So I’ve been trying something more quixotic – writing my entire client side in Rust, aside from the loading function below. init takes care of fetching & loading the wasm file. I pass the URL of the server in from JS so that I don’t need to recompile the Rust code when deploying.

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Applicatives and Monoids

I’m tinkering with bits of a new Haskell Postgres library. It’s very much not ready for others to use, but I’m using an interesting type, new to me, which I want to share. Maybe someone can point me at prior art, also.

The main idea is that as we build up decoding functions, we want to collect type names at the same time. We’ll use the type names at runtime, to check that Postgres sends what Haskell expects. If not, we’ll use them in an error message.

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Many ways to load modules

I’ve been confused for years by variations of the :load command in GHCi. So much so it often keeps me from using GHCi.

The GHC manual mentions:

• :load
• :add
• :reload
• :module
• import

That’s a lot of different commands!

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