diff --git a/_posts/2020-07-24-isomorphic-apps copy.md b/_posts/2020-07-24-isomorphic-apps copy.md new file mode 100644 index 0000000..a8a6053 --- /dev/null +++ b/_posts/2020-07-24-isomorphic-apps copy.md @@ -0,0 +1,92 @@ +--- +layout: post +title: "More Isomorphic Desktop Apps with Rust" +description: "They suck less now." +category: +tags: [rust, javascript, webassembly] +--- + +I wasn't expecting to write this, but it's 2020 and we could all use a win. When last I addressed +using WASM + Electron to write desktop applications in Rust, there were ultimately too many issues +to recommend this combination as feasible. Since then, there's been a lot of progress, and after +finding out [the biggest problem] has been addressed, I decided it was time to take another look at +where things stand. + +# Loading local WASM blobs + +Previously, the most significant issue was trying to actually load WASM blobs in Electron. This +problem was the result of a combination of factors: + +1. When using streaming WASM blobs + ([`WebAssembly.instantiateStreaming()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/instantiateStreaming)), + the blob must be returned with a `Content-Type` header of `application/wasm`. + - If the full WASM blob is loaded into memory first, the MIME type restriction does not apply. +2. When Chrome loads `file://` URLs, the `Content-Type` is unset. +3. Webpack prioritizes streaming WASM whenever available, and if it fails, has no graceful fallback. +4. When building Rust WASM binaries using `wasm-bindgen`, webpack is used to generate JS bindings + for the WASM blob. + +Putting all this together: + +- Electron loads the JS created by `wasm-bindgen`/webpack +- This JS file calls attempts to load the WASM blob, which just so happens to be located on disk +- Because the MIME type isn't set, loading fails + +This was a well-known issue; +[emscripten](https://github.com/emscripten-core/emscripten/blob/8914c5cd5e4ac35a806430e8c77c88cd8c65b234/src/preamble.js#L2295) +even included a graceful fallback for this scneario. It was possible to tweak the JS created by +`wasm-bindgen` to load WASM, but using `sed` to edit generated code will eventually lead to madness. + +I'm unable to figure out when exactly it changed, but requesting WASM blobs from `file://` URLs in +Chrome now sets the MIME type, and thus the blob is loaded correctly. Additionally, recent changes +to be released in Webpack 5 (specifically the `asyncWebAssembly` and `importAsync` +[experiments](https://webpack.js.org/configuration/experiments/)) enable loading WASM without a +separate launcher script. + +# The evolution of Rust + +Rust as a language has also made a great deal of progress since late 2018. Previously, some +widely-used crates (like `stdweb`) required a `nightly` Rust compiler to function. Now, nearly +everything compiles on `stable`. In addition, now that Rust supports `async/await`, it's much easier +to interact with Javascript. It's still necessary to use some crates like `wasm_bindgen` to assist +the interaction, but Rust can now make use of the same asynchronous paradigms that have proven to be +incredibly effective in Javascript. + +There's also been great progress on some crates to interact directly with the browser; `web-sys` and +`js-sys` enable easier interoperation with the browser, where previously users didn't have these +options available. + +The tooling and documentation has improved as well. `wasm-pack` has proven itself as a reliable "one +stop shop" tool for managing WASM projects. While using `wasm-bindgen` and `webpack` directly are +still necessary for building Electron apps (due to Webpack v5 not yet released), this should change +in the near future as well. + +# New examples + +(need to put some screenshots and link to the new examples here) + +# Outstanding issues + +While I haven't been directly involved in any of the progress made to improve Rust + WASM, it's +incredibly encouraging to see just how far everything has come. Seeing where the ecosystem stands +now, I think using Electron + Rust to build desktop applications is _feasible_. Not necessarily a +_good_ idea, not that it offers any specific benefit over using Javascript/Typescript, just that +it's now _feasible_. + +Looking forward, the things I think could be beneficial to address are: + +- Template/starter project examples + - Being able to `yarn create` a project and have it already set up with two-way JS to Rust + bindings would go a long way towards reducing the currently painful setup using either + `wasm-bindgen` or `wasm-pack`. +- Comparisons to Typescript and Neon + - Is there a development or performance benefit that comes from using Rust instead of Typescript? + WASM might execute faster, but Rust might be more tedious to develop. It would be useful to port + an existing (small) application to Rust and see what the differences are. That said, while + benchmarking WASM vs. Javascript is at least theoretically possible to do in a systematic + manner, evaluating the developer experience is like a case-by-case determination. + - Instead of embedding Rust in Electron by way of WASM, [Neon] can be used to develop extensions + that run natively and are "glued" to Electron via Javascript. Further investigation to clarify + the pros/cons of each approach would be helpful; are there situations in which WASM offers + benefits over Neon? Vice-versa? Both WASM and Neon already require more complex setups than + typical JS/TS setups.