Module resolution: default import does not work with `type: module` about typescript

[fatcerberus]

For the record:
https://arethetypeswrong.github.io/?p=next%4014.1.3

[RyanCavanaugh]

What you're describing - that package authors tell TS how their package works - is what's happening, it just happens that next is telling TS the wrong thing.

[RyanCavanaugh]

next is inferred to be a CommonJS module because it doesn't have type: "module" in its package.json and doesn't have any other indication that it can be loaded as an ESM module.

See #50058 (comment)

[mohd-akram]

I don't fully understand that comment. Next does a default export and I do a default import. It seems simple enough that this should work? Why is the type of next considered when that information is already specified in declaration files via either export = or export default?

[RyanCavanaugh]

The comment explains all of this

[mohd-akram]

It doesn't address why TypeScript considers type of an imported module rather than simply accepting what module authors specify in their type files. For distinguishing between the export default example and the MyFunction one in your comment, the library author can use export default and export = respectively. This is how it already works in non-Node16 modes.

[RyanCavanaugh]

If you write your exports in ESM syntax, but the package itself is CJS (which it is), then Node16 module mode says to respect what the package says, because that's what Node does.

[mohd-akram]

@RyanCavanaugh I think that's a mistake. The exports are eventually transformed into ESM imports according to Node.js. Per Node.js, that transformation uses static analysis and its outcome is unknown beforehand. Accepting what the types say lets those who do know - the library authors - inform TypeScript of the final shape of the library.

[typescript-bot]

This issue has been marked as "Working as Intended" and has seen no recent activity. It has been automatically closed for house-keeping purposes.