Dynamic import does not respect --allowSyntheticDefaultImports

[aluanhaddad]

TypeScript Version: 2.5.0-dev.20170725

Code

// A *self-contained* demonstration of the problem follows...
// --module esnext --allowSyntheticDefaultImports (or with --module system)
import('jquery').then(({default: $}) => $('div'));

Expected behavior:
The shape of the dynamically imported jquery's module namespace object includes a default member having the type JQueryStatic<HTMLElement> as it does when using the static import syntax as in

import {default as $} from 'jquery';
$('div');

under --module system or with --allowSyntheticDefaultImports

Actual behavior:

error TS2459: Type 'JQueryStatic<HTMLElement>' has no property 'default' and no string index signature.

Note that this is tricky since the expected mapping does not quite correspond to that of a static import since import('jquery').then($ => $('div')); probably should not work, but the default member should be present.

[Jessidhia]

This can be tricky as it won't behave correctly at runtime in webpack either.

I'd recommend just never using dynamic import with a commonjs module.

[aluanhaddad]

I'd recommend just never using dynamic import with a commonjs module.

Do you mean that modules transpiled from ESNext to CommonJS should never use dynamic import, that modules in CommonJS format should never be imported using the construct, or both?

[Jessidhia]

While we are stuck in a transpiling world, it’s safe to import transpiled modules (that don’t do add-module-exports shenanigans), but it will not work with transpiled modules either in real module implementation.

…

On Sat, Jul 29, 2017 at 4:53 Aluan Haddad ***@***.***> wrote: I'd recommend just never using dynamic import with a commonjs module. Do you mean that modules transpiled from ESNext to CommonJS should never use dynamic import, that modules in CommonJS format should never be imported using the construct, or both? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#17444 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAEdfSs4V_7RiYeFp_TCR_r4ehmut9Ihks5sSjwugaJpZM4OkvHt> .