BiomeJS

[darrylyeo]

• Reduce tooling dependencies by replacing ESLint and Prettier with Biome
• Smarter import sorting that is "group"-aware (preserves double line breaks) and places types first
• Catch some additional issues in CSS and React

Known caveat:

• Biome doesn't currently have a built-in way to flag unsafe TypeScript as clauses (i.e. the equivalent of @typescript-eslint/no-unsafe-type-assertion)

[polymutex]

Well I like the extra speed, but not the loss of type safety... Can we keep ESLint, but only enforce it in CI and in pnpm run check:all?

Also, do Biome's annotations still show up in VSCode? .vscode/extensions.json doesn't seem to have an entry, did you mean to add biomejs.biome?

[polymutex]

cc @lucemans, who mentioned that the spread of top-level files we have is unwieldy (which I agree with). This change gets rid of .prettierrc, .editorconfig, eslint.config.mjs, and replaces them with a single biome.jsonc. Seems like a win in terms of tooling simplicity and of top-level file count.

That said, I am very adamant that we keep enforcing @typescript-eslint/no-unsafe-type-assertion. But it may be OK to hide the config to enforce this out of the top-level directory and shove it inside deploy or something, where only CI would look at it. That way it wouldn't clutter up the top level. And it would be OK to use a non-default path for that, because it's not meant to be used by individual developers themselves. Just by CI, which can bear to have its own non-default configuration.