Type-only TypeScript files break development and Webpack plugin

[denis-sokolov]

A type-only file is not emitted. This prevents the app from loading in the development mode and crashes Webpack plugin at build time.

// types.ts
export type A = string;

// index.ts
import type { A } from './types';
const a: A = 'a';
console.log(a);

Type-only TS files are not a corner case, it is common to define a data model in types in a stand-alone file for organization, for more convenient reuse.

Related, possibly a duplicate, depending on perspective: #1509.
@melissamcewen

[melissamcewen]

I tried this out locally and I didn't get any errors, but I might have missed something. If you have your code on Github that would help.

[denis-sokolov]

Understood. I was hoping it’s not specific to my configuration. I will find time, investigate this in more detail, and, if applicable, prepare a reproduction. Please excuse a delay I need for that.

[denis-sokolov]

I have made a reproduction for the problem. It requires a type-only .ts file and a re-export.

See my reproduction repository. It is made from a Snowpack template with a single commit on top that only adds the foo directory. In it there’s a type-only file a.ts, and a file with a function b.ts. Both are re-exported in index.ts.

The issue happens after a build. You can run npm run build or use my pushed build output for convenience. Notice that the directory build/_dist_/foo/ has no a.js file, due to #1509. But build/_dist_/foo/index.js has a export * from "./a.js" statement that will fail even in development.

Let me know if I can provide any more detail! @melissamcewen

[denis-sokolov]

This is present in the latest 3.0.11.