@babel/plugin-transform-typescript removes regular imports

[hulkish]

Bug Report

Current Behavior
this logic seems to be introducing a bug for non-typescript code.

Specifically, it is incorrectly removing a regular module import.

Input Code

import foo from 'foo';
export bar from 'bar';
export * as baz from 'baz';

export default class Foobar {}

Expected output

import foo from 'foo'; // why is this line is removed?
import _bar from 'bar';
export { _bar as bar };
import * as _baz from 'baz';
export { _baz as baz };
var Foobar = function Foobar() {};
export { Foobar as default };

Actual output

import _bar from 'bar';
export { _bar as bar };
import * as _baz from 'baz';
export { _baz as baz };
export default class Foobar {}

Babel Configuration (.babelrc, package.json, cli command)

{
  "presets": ["@babel/preset-typescript", { isTSX: true, allExtensions: true }]
}

Environment

• Babel version(s): @babel/core@7.3.4, @babel/preset-typescript@7.3.3
• Node/npm version: npm@, node@10.15.3
• OS: macOS@10.14.1
• Monorepo: yes, but doesn't matter - happens anywhere.
• How you are using Babel: directly using transformFileSync() from @babel/core

Possible Solution
Fix issue in @babel/plugin-transform-typescript

Additional context/Screenshots
N/A

[babel-bot]

Hey @hulkish! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
for an invite.

[nicolo-ribaudo]

That is the expected behavior: https://www.typescriptlang.org/play/index.html#src=import%20foo%20from%20'foo'%3B%0A%0Aexport%20default%20class%20Foobar%20%7B%7D

In TypeScript, unused imports as considered as type imports and thus removed.

[hulkish]

@nicolo-ribaudo How is this considered safe? What if foo has side effects? This seems very wrong to me.

[nicolo-ribaudo]

I agree that it is unexpected, but it is a bug with the TypeScript language. We won't diverge from their implementation, so it needs to be fixed upstream first.

If you need foo for its side effects, you can use import "foo" and it shouldn't be removed.

[hulkish]

Understood, thanks for the explanation!