Is it me or does this project tries to do too many things at once? "Bun is an npm-compatible package manager", and an http server, and a websocket server, and a test library, and a bundler, and... why?
Nowadays if you start a new Javascript project you need to setup, vite/esbuild/webpack, eslint/oxlint/biome, prettier, typescript, etc, that is a ton of dependencies that YOU need to maintain for years, and if it is part of the tool you are using, then you don't, ideally there shouldn't be a breaking change, let's see how bun manages that when the time comes.
I am waiting for bun or a tool that has everything I need to bundle my frontend app, I'm very tired of fiddling with all the dependencies and try to make to work every dependency together, I have a legacy project that I work on, I would have migrated a long time ago to another tool, but there is none that would fix the current issue and it's managing the project build, test, formatter, lint dependencies, after using Rust I feel super frustrated with the Javascript ecosystem state.
Also you asked why? I want to work on the project, there is already a lot of work to maintain the dependencies up to date, the tooling should not be part of that work.
That's a choice YOU make, not everyone makes that choice, especially because they want to be able to continue working on a project for months/years without accruing automatic technical debt as all those projects move forward without actually thinking about backwards compatibility.
JS doesn’t have anything like that, which is why projects like Deno, Bun, Biome, etc are interesting. These projects explore how JS can also get a great out of the box experience without requiring the complex setup and maintenance steps that so many existing tools require.
Besides, professionally, you normally don’t make the choice in a vacuum. Linters, package managers, testing, bundling/building, type safety, and even formatting are all very useful in big projects with lots of people. So you often don’t get to say “ah we just won’t have unit tests because jest doesn’t care enough about backwards compatibility.”
When things are not that coupled, independent components you bring together, you can update the webserver, and/or some components, and keep the old version of the test library for now, until you decide it's time to upgrade.
I'm currently fighting PHP + Laravel. I want to upgrade PHP but I can't because the version of Laravel I'm using depends on an older version of PHP. So I have to upgrade them both in lockstep anyway.
Regarding runtime libraries, it’s similar to the battery-included approach of go or python, you get what you need to get started out of the box and only reach for dependencies when you want to go further. Testing library, an http server, a websocket server that’s perfectly reasonable to have as core library of a runtime developed to run web servers.
I however find Bun more useful as a Swiss army knives, to use with nodejs, to reduce the number of development dependencies.