Type-only auto imports

[andrewbranch]

Auto imports will not use type-only imports, unless an import specifier can be added to an existing type-only import, and usage of the import occurs at a position where a type-only alias can be used:

import type { PathLike } from 'fs'

const dir: Dir/* | adds 'Dir' to existing type-only import */

On the other hand, if the import can be added to an existing type-only import, but is used in a position that is invalid for a type-only alias, the type-only import will be converted to a regular import:

import type { PathLike } from 'fs'

const dir = new Dir/* | adds 'Dir' to existing import and deletes 'type' */

From feedback in #36038, it sounds like we may also need to follow up and create a “hard mode” where an existing type-only import never converts to a regular import and blocks regular imports from that module from being added by auto-import. Such a hardline approach would probably frustrating, unexpected, and unnecessary for most users (as evidenced by the fact that #36002 was filed as a bug immediately) if enabled by default, but it’s justifiable to say “if I go through the trouble to write a type-only import, I really want to make sure I don’t regular-import that module into this one.”

Fixes #36002

[mjbvz]

Description of the new behavior sounds good to me. Thanks for looking into this!

[sheetalkamat]

Apart from question on the test change looks good.

[sheetalkamat]

Why was this deleted, is it because similar test already exists?

[andrewbranch]

Yeah, it was actually verifying a behavior that we actually don’t want anymore (using a type-only import for new imports of types), and reversing that behavior makes it redundant with many others.

[DimitryDushkin]

Hey! Could you please clarify how to enable auto-import with type for first import? AFAIK this pull can auto-import with type if such import already exists.

[andrewbranch]

An auto import will only be written as a type-only import if not doing so would result in an error. For that to be true, your tsconfig must have importsNotUsedAsValues: "error", and the place where you’re performing the auto-import must be a type position.

[DimitryDushkin]

Thank you @andrewbranch !

[ghost]

An auto import will only be written as a type-only import if not doing so would result in an error. For that to be true, your tsconfig must have importsNotUsedAsValues: "error", and the place where you’re performing the auto-import must be a type position.

Awesome! It works, but.. the compiler gets stuck after such an error raises up and any change in a document does not invoke compiling. Am I the only one?

[Kos]

For those who find their way here from web search: The importsNotUsedAsValues tsconfig option is now deprecated, and the new one to look at is verbatimModuleSyntax. I confirm vscode generates import type after enabling this flag.

[Hemaolle]

For those who find their way here from web search: The importsNotUsedAsValues tsconfig option is now deprecated, and the new one to look at is verbatimModuleSyntax. I confirm vscode generates import type after enabling this flag.

verbatimModuleSyntax was introduced in TS 5.0, so check your TS version before taking that option into use.