Fastify autoload throwing errors about ts in projects that don't use ts

[bcomnes]

Prerequisites

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

Fastify version

4.x.x

Plugin version

5.3.0

Node.js version

18.x

Operating system

macOS

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

Linux and macOS 12.5.1

Description

It looks like #264 is breaking non-ts fastify projects.

What was previously working now gets the following error:

Error: @fastify/autoload cannot import plugin at '/Users/bret/Developer/breadcrum.net/plugins/accepts.js'. To fix this error compile TypeScript to JavaScript or use 'ts-node' to run your app.
    at findPlugins (/Users/bret/Developer/breadcrum.net/node_modules/@fastify/autoload/index.js:224:17)
    at async autoload (/Users/bret/Developer/breadcrum.net/node_modules/@fastify/autoload/index.js:28:22)

The accepts plugin mentinoned in the error is very simple and does not use TS

import fp from 'fastify-plugin'

/**
 * This plugins adds fastify-auth
 *
 * @see https://github.com/fastify/fastify-accepts
 */
export default fp(async function (fastify, opts) {
  fastify.register(import('@fastify/accepts'))
}, {
  name: 'accepts',
  dependencies: []
})

Steps to Reproduce

Try to load the above plugin on a ts free auto-load project set to esm module mode.

import fp from 'fastify-plugin'

/**
 * This plugins adds fastify-auth
 *
 * @see https://github.com/fastify/fastify-accepts
 */
export default fp(async function (fastify, opts) {
  fastify.register(import('@fastify/accepts'))
}, {
  name: 'accepts',
  dependencies: []
})

Here is a reproducible example generated from the fastify-cli and then converted to esm.

https://github.com/ballpit/fastify-autoload-bug

Downgrading fastify-autoload to 5.2.0 fixes the build.

Expected Behavior

That projects not using TS don't throw errors about ts.

[bcomnes]

I added a reproducible example generated from the fastify-cli:

https://github.com/ballpit/fastify-autoload-bug

[bcomnes]

Looks like if you simply generate a cjs scaffold that also breaks.

Error: @fastify/autoload cannot import plugin at '/Users/bret/Developer/scratch/common-fast0-bug/plugins/sensible.js'. To fix this error compile TypeScript to JavaScript or use 'ts-node' to run your app.
    at findPlugins (/Users/bret/Developer/scratch/common-fast0-bug/node_modules/@fastify/autoload/index.js:224:17)
    at async autoload (/Users/bret/Developer/scratch/common-fast0-bug/node_modules/@fastify/autoload/index.js:28:22)

[bcomnes]

@kylerush any ideas on how to fix?

[mcollina]

I've just shipped v5.3.1 with a revert.