ESM imports are failing

[gajus]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

N/A

Plugin version

9.0.4

Node.js version

19.9.0

Operating system

Linux

Operating system version (i.e. 20.04, 11.3, 10)

13.2.1

Description

Importing in ESM workspace is failing with an error:

import { fastifyCookie } from '@fastify/cookie';
         ^^^^^^^^^^^^^
SyntaxError: Named export 'fastifyCookie' not found. The requested module '@fastify/cookie' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:

import pkg from '@fastify/cookie';
const { fastifyCookie } = pkg;

Steps to Reproduce

Add "type": "module" to package.json.

Expected Behavior

Should work with ESM imports.

[gurgunday]

There isn’t a named export called fastifyCookie

[gurgunday]

import pkg from '@fastify/cookie';
const { fastifyCookie } = pkg;

should work

[gajus]

But that fails TypeScript types.

[gajus]

For context, const fastifyCookie = await import('@fastify/cookie') works as expected.

[gurgunday]

For context, const fastifyCookie = await import('@fastify/cookie') works as expected.

If you're looking for the equivalent of this import, it would be the following:

import fastifyCookie from '@fastify/cookie';

It uses default exports - notice how there aren't curly brackets ({})

[gajus]

Ah, misread the error indicators in VSCode.

import fastifyCookie from '@fastify/cookie';

The error is coming from ESLint:

Using exported name 'fastifyCookie' as identifier for default export.eslint[import/no-named-as-default](https://github.com/import-js/eslint-plugin-import/blob/v2.28.1/docs/rules/no-named-as-default.md)

https://github.com/import-js/eslint-plugin-import/blob/v2.28.1/docs/rules/no-named-as-default.md

i.e. Looks like ESLint thinks that there is fastifyCookie named export, but there isn't.

[gajus]

I can only assume that this is because of:

export const fastifyCookie: FastifyCookie;

which exists inside of the namespace fastifyCookie.

I am not familiar with TypeScript namespaces, so cannot comment whether this is an issue with this package or ESLint rule.

[Uzlopak]

According to the eslint rule, this is a warning for you as an end user, as it could be that you wanted to use the named import and not the default import. Nothing to do with us.

[gajus]

But there is no named export.

[Uzlopak]

fastify-cookie/plugin.js

Line 214 in 290e559

fastifyCookie.fastifyCookie = fastifyCookie

[gajus]

So that takes us to the original issue.

import { fastifyCookie } from '...'

Does not work

[Uzlopak]

Please provide a repo

[gajus]

There isn’t a named export called fastifyCookie

This was already confirmed to be an issue.

[gurgunday]

fastify-cookie/plugin.js

Line 214 in 290e559

fastifyCookie.fastifyCookie = fastifyCookie

That will not work if that was the intention. To do an ESM named export, a property of module.exports must be set like so: module.exports.fastifyCookie = fastifyCookie

I haven't properly looked at the code but ESLint might be mistakenly thinking that a named export exists while it doesn't. Why do you import it like that anyway? This is the de-facto way of registering plugins/routes:

// await is optional *here*
await fastify.register(import("@fastify/cookie"), {
});