The `./styles` subpath export has no `types` condition — side-effect import errors under TypeScript 6

[BSalaeddin]

Problem

packages/next/package.json (and the sibling framework packages that ship the same pattern) exports the stylesheet as a bare string:

"./styles": "./dist/tailwind-prefixed.css"

TypeScript 6.0 started type-checking side-effect imports, so a consumer on TS 6.x doing the documented

import '@upupjs/next/styles'

now fails to resolve declarations for the subpath (no types condition, no declaration file), forcing every TS 6 consumer to hand-write an ambient declare module '@upupjs/next/styles' shim.

Hit in production use: DevinoSolutions/GetItDone's TS 6.0.3 upgrade needed a local upup-styles.d.ts workaround for exactly this (verified against @upupjs/next / @upupjs/core 3.1.0, 2026-08-14).

Fix options

1. allowArbitraryExtensions-style declaration (TS-official mechanism): ship dist/tailwind-prefixed.d.css.ts next to the CSS and add a types condition:

   "./styles": {
       "types": "./dist/tailwind-prefixed.d.css.ts",
       "default": "./dist/tailwind-prefixed.css"
   }

2. Or a plain empty ambient declaration (declare module '@upupjs/next/styles';) shipped in dist and referenced by a types condition.

Either removes the consumer-side shim with no runtime change. Worth sweeping every framework package (react, vue, svelte, vanilla, angular, preact, next) that exposes a CSS subpath the same way.

[AminDhouib]

Fixed in #363 (targeting dev).

Mechanism. All seven UI packages (react, vue, svelte, vanilla, angular, preact, next) now export the stylesheet with a types condition backed by a generated empty-module declaration:

"./styles": {
    "types": "./dist/styles.d.ts",
    "default": "./dist/tailwind-prefixed.css"
}

I tested both options from the issue plus two variants against real packed tarballs, and all four resolve — including dist/tailwind-prefixed.d.css.ts without the consumer enabling allowArbitraryExtensions, since the types condition targets the file directly rather than going through extension inference. Since correctness didn't decide it, I went with option 2 (a plain .d.ts containing export {}): it doesn't depend on the arbitrary-extension feature, the export marker makes it an explicit module rather than a global script, and it holds under skipLibCheck: false.

Each package also gets "typesVersions": { "*": { "styles": ["dist/styles.d.ts"] } }, because moduleResolution: "node10" ignores exports entirely — TS says so directly: "There are types at .../dist/styles.d.ts, but this result could not be resolved under your current 'moduleResolution' setting."

No runtime change. The default condition still points at the same unmoved dist/tailwind-prefixed.css, and require.resolve / import.meta.resolve still land on the CSS for all seven packages. The declaration is emitted by a build step (scripts/emit-styles-dts.mjs wired into each package's build:css), not hand-placed in the gitignored dist.

Verification. A real consumer — all tarballs pnpm packed and extracted into node_modules, one side-effect import per package, tsc --noEmit.

Before, on typescript@6.0.3 and @7.0.2, under both bundler and node16, reproducing your report on every package:

src/index.ts(1,8): error TS2882: Cannot find module or type declarations for side-effect import of '@upupjs/react/styles'.
...
src/index.ts(7,8): error TS2882: Cannot find module or type declarations for side-effect import of '@upupjs/next/styles'.

After: exit 0 on typescript@5.9.3, @6.0.3 and @7.0.2 × bundler/node16, plus node10 on TS 6 via the typesVersions fallback. (TS 5.9.3 was green before the change too — it doesn't type-check side-effect imports, which is why this only surfaced on the 6.x upgrade.)

The subpath shape is now guarded by a unit-tested check called from the package-smoke tarball consumer, so dropping the types condition, moving the CSS, or shipping a tarball without the declaration turns CI red even though the CSS itself would still be present.

A patch changeset is included, so once #363 lands and releases you can drop the local upup-styles.d.ts shim in GetItDone.