[Discussion] make Hono ESM only in next major version

[BlankParticle]

Hono should drop CJS support in next major version and go ESM only

right now Hono is published as a dual package with both cjs and esm support,
but there isn't any widespread usage of hono in pure cjs context [sourcegraph search for require("hono")]

there is lot of typescript code that looks like imports but is compiled down to CJS under the hood, but I think its fine. Current supported Node releases are 22, 24, and 26. Node 20 is EOL. require(esm) is already supported across all supported node versions including node 20. Node is only one of Hono's target runtime where we need CJS and that issue is mostly solved, on runtimes like Bun/Deno/Cloudflare we don't have any use for CJS.

So I think we should, raise minimum supported version for hono to node >=22 and remove all tooling for CJS and publish hono@5 (next major) as a ESM only version.

Refs:

• https://antfu.me/posts/move-on-to-esm-only
• https://e18e.dev/blog/migrating-the-ecosystem-to-esm.html
• https://storybook.js.org/blog/storybook-is-going-esm-only

Open PR: #5114

[yusukebe]

So I think we should, raise minimum supported version for hono to node >=22 and remove all tooling for CJS and publish hono@5 (next major) as a ESM only version.

Agree! Let's do it.

[BarryThePenguin]

I'm guessing there would be a list of things that would be good to get into a v5? Splitting out adaptors into their own packages would be another good candidate.

Adopting tsdown, similar to the middleware monorepo, would work well

[yusukebe]

I'm guessing there would be a list of things that would be good to get into a v5

Good idea. Created #5106

[43081j]

Adopting tsdown, similar to the middleware monorepo, would work well

Given this would be a switch to esm only, is there still a need for a bundler at all?

You could just run tsc since the build script is only doing validation and some tidying 👀

[BlankParticle]

Adopting tsdown, similar to the middleware monorepo, would work well

Given this would be a switch to esm only, is there still a need for a bundler at all?

You could just run tsc since the build script is only doing validation and some tidying 👀

there is some extra tooling like https://github.com/honojs/hono/blob/main/build/remove-private-fields.ts
other than that its using esbuild as replacement for tsc, as all source files are translated 1:1
but I guess bundling would be nice, so instead of having lots of source files we can only bundle the exported entry points