Make it possible to disable code splitting

[tats-u]

Clear and concise description of the problem

tsup can disable code splitting by the following config:

import { defineConfig } from "tsup";

export default defineConfig({
  entry: ["./src"],
  format: "esm",
  splitting: false, // !!!!!! HERE !!!!!
  dts: true,
  target: "es2021",
});

However, tsdown doesn't have such a splitting property.
Disabling code splitting improves readability and analyzability of output JS code.

tsup's doc: https://tsup.egoist.dev/#code-splitting

Suggested solution

Support splitting property

Alternative

Use tsup instead of tsdown. tsup has already been able to disable splitting.

Additional context

I tried tsdown in my packages in https://github.com/tats-u/markdown-cjk-friendly/, but gave up due to the lack of this feature.

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[sxzz]

Now unsupported because of Rolldown

[tats-u]

I see.

[tats-u]

I found it's not supported in Rollup either.

rollup/rollup#2756

[sxzz]

Is there any use cases that need disabling code splitting?

[tats-u]

remarkjs/remark#1422

It looks like one of the main maintainers of remark prefer to keep .ts source and built .d.ts/.js 1:1 (one pair of .d.ts/.js per .ts).
He wants library authors to keep the published package source easily-analyzable/debuggable.

[tats-u]

I personally prefer to bundle source files into single pair of .d.ts and .js.

By this, a JS runtime has only to open and parse just one JS file.

[sxzz]

Maybe preserveModules is more like you needed (but Rolldown haven't implement preserveModules yet)

[tats-u]

Is it a Rollup's option? I can't try it today because tsup is basically esbuild-powered. I couldn't find such an option in tsup's website.

[lishaduck]

Is it a Rollup's option?

Yeah, it's this: https://rollupjs.org/configuration-options/#output-preservemodules

[tats-u]

I googled it and it looks like what I've wanted. However I can't try it today unfortunately because I don't use Vite or Rollup to build my libraries.