fix(lsp): code action imports of types are import type

[kitsonk]

Fixes: #10776

[lucacasonato]

Wouldn't enabling "importsNotUsedAsValues": "error" result in more diagnostics than in the CLI (where this is not set to "error")?

I.e. wouldn't this error in LSP, but not deno run?

import { Foo } from "https://example.com/foo.ts";
const foo: Foo = { };

[kitsonk]

It does but, a) there is no other way to get TypeScript to import as import type when auto importing types, and b) while Deno CLI can run such code, it runs the risk of being "transpile unfriendly", so it encourages better code anyways. I would be for setting it to "error" for CLI as well, as it avoids some problems people can get themselves into (like doing an export * from "foo" that is doing a named import from some other module, which we have seen in the wild).

Given the module a.ts of:

export interface A {
  a: string;
}

export const a = "a";

The following would have no diagnostics:

import { A, a } from "./a.ts";

const b: A = {
  a,
};

console.log(a);

The following would also not have any diagnostics:

import type { A } from "./a.ts";

const b: A = {
  a: "a"
};

console.log(a);

The following would have This import is never used as a value and must use 'import type' because 'importsNotUsedAsValues' is set to 'error'. for the import statement:

import { A } from "./a.ts";

const b: A = {
  a: "a"
};

console.log(a);

[lucacasonato]

Mh - this feels like it would slot into a larger discussion about the importsNotUsedAsValues option. We used to have it set to "error" (#7413), but then reverted back to "remove" a few weeks later (#7800). The "remove" option is unambiguous already with isolatedModules: true, so I don't know.

Very hesitant to land this in LSP without also landing for the rest of CLI. But doing so would result in a lot of churn for users for no big benefit that I can see.

[kitsonk]

🤷 I won't lose any sleep over it. It was only because people were reporting it as an issue.

[kitsonk]

Let's close this, as the potential pain ain't worth the squeeze.