@rollup/plugin-typescript / `{type X}` imports are not elided correctly

[arklanq]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 11.1.3
• TypeScript package version: 5.2.2
• Rollup Version: 3.29.2
• Operating System (or Browser): macOS / Node.js
• Node Version: v18.17.0
• Link to reproduction: https://stackblitz.com/edit/rollup-repro-hjdtrw?file=README.md

Please read README.md first.

Expected Behavior

Import such as import {type X} from 'y':

// Source code
import {type App} from './App.js';

... should be elided and dropped entirely.

Actual Behavior

... but instead, the import is preserved:

// Output code
import './App.js';

Another example

On the other hand, import type {X} from 'y' works perfectly fine

// Source code
import type {App} from './App.js';

// Output
// No import is generated for the above source code

Additional Information

• First, I thought that the odd bundler misbehavior was caused by the verbatimModuleSyntax option in tsconfig.json, but after a quick analysis, I have found out there is no difference if this option is on or off.
• tsc also generates code incorrectly. It properly elides imports but does not drop them entirely as it should. See repro for more details, I have covered this topic there also. I have not found any open issue about this in the typescript repo.

Related

• https://devblogs.microsoft.com/typescript/announcing-typescript-4-5/#type-on-import-names
• https://typescript-eslint.io/rules/no-import-type-side-effects/

[gwicksted]

This works with the latest version of rollup as long as:

• you have included the .ts file (containing the import type statement) for compilation in your tsconfig.json that the @rollup/plugin-typescript plugin uses.

• you are either: a. using the main tsconfig.json file; or, b. not using --configPlugin typescript which causes your main tsconfig.json file to be used instead of the one pointed to in your rollup.config.ts file. In other words, use rollup.config.js