Type only imports can lead to unnecessary module load

[jordanebelanger]

Version

24.0.2

Platform

Darwin Mac.lan 24.4.0 Darwin Kernel Version 24.4.0: Fri Apr 11 18:32:50 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6041 arm64

Subsystem

No response

What steps will reproduce the bug?

Install a package as a dev dependency, and then do a type only import like below:

import { type FromSchema, type JSONSchema } from 'json-schema-to-ts'

How often does it reproduce? Is there a required condition?

100%

What is the expected behavior? Why is that the expected behavior?

If an import only includes TypeScript types—even if it doesn’t use the import type { ... } shorthand syntax, such as import { type FromSchema, type JSONSchema } from 'json-schema-to-ts' —the module should not be loaded at runtime, just as it wouldn’t be with the import type shorthand: import type { FromSchema, JSONSchema } from 'json-schema-to-ts'.

What do you see instead?

Despite only importing types, the module is still loaded at runtime, leading to an error like:
Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'json-schema-to-ts'
if the package is only installed as a dev dependency.

Of course a user can rely on using the shorthand notation for a type only import to avoid this issue, but this is a bit quirky and hard to enforce in a large code base without using a well setuped prettier/biome/etc.

On my hand I had this issue because I used a codemod to convert my codebase and automatically fix verbatimModuleSyntax issues.

Additional information

It would be great to fix this issue and avoid people occasionally scratching their head at this despite a work around being available.

[marco-ippolito]

If its a type only import it should be: (which can be stripped)

import type { FromSchema, JSONSchema } from 'json-schema-to-ts'

Otherwise it cannot be stripped since:

import {} from 'json-schema-to-ts'

is a valid import

[jordanebelanger]

If its a type only import it should be: (which can be stripped)

import type { FromSchema, JSONSchema } from 'json-schema-to-ts'

Otherwise it cannot be stripped since:

import {} from 'json-schema-to-ts'

is a valid import

Maybe I am misunderstanding, but if it's only types being imported we can safely assume the user is not trying to do import {} from xyz

[marco-ippolito]

That assumption is not correct:
Let's say our index.ts import a bar.ts

// index.ts
import {} from './bar.ts';

// bar.ts
console.log("Hello World");

Output is:

> node index.ts
Hello World!

If we change index.ts to

import type {} from './bar.ts';

Output is:

> node index.ts

Basically {} is a valid non erasable import while type {} is erasable

[jordanebelanger]

I see what you mean ok, I guess technically speaking someone doing:

import { type X } from 'xyz'

might be attempting to import only the type X from there while simultaneously also intending to run code from inside the module, fair enough.

[jordanebelanger]

Closing the issue, thank you for the clarification @marco-ippolito