Typescript Support: Origin is undefined

[bkawk]

Prerequisites

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

Fastify version

3.0.0

Plugin version

3.0.0

Node.js version

v14.15.4

Operating system

macOS

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

11.5.2

Description

Following the async example in a typescript environment with fastify plugin results in origin is undefined

Steps to Reproduce

Trying to set up CORS for fastify vai the fastify-plugin in a fairly strict typescript environment. The docs showing the async configuration https://github.com/fastify/fastify-cors#configuring-cors-asynchronously

import fp from 'fastify-plugin';
import cors from 'fastify-cors';

export default fp(async (fastify) => {
  fastify.register(cors, () => (callback: any): void => {
    let corsOptions;
    if (/localhost/.test(origin)) {
      corsOptions = { origin: false };
    } else {
      corsOptions = { origin: 'www.mywebsite.com' };
    }
    callback(null, corsOptions);
  });
});

The error I get is

'origin' is not defined.eslintno-undef
Cannot find name 'origin'.ts(2304)

How do I define origin?

If I try the non-async example from the docs origin is still undefined

import fp from 'fastify-plugin';
import cors from 'fastify-cors';

export default fp(async (fastify) => {
  fastify.register(cors, {
    origin: (origin, callback) => {
      // eslint-disable-next-line no-console
      console.log(origin); //<======== undefined
      if (/localhost/.test(origin)) {
        callback(null, true);
      } else {
        callback(new Error('Not allowed by CORS'), false);
      }
    },
  });
});

Expected Behavior

I expect typescript to not complain about origin being undefined

Demo code can be found here https://github.com/bkawk/fastify-swagger/blob/cors/src/plugins/cors.ts

[mcollina]

Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[bkawk]

Would you like to send a Pull Request to address this issue? Remember to add unit tests.

Unfortunately, this issue goes beyond my understanding, otherwise, I'd love to help out

[damey2011]

This still happens with Fastify 4 and Fastify CORS 8.1.0

[Eomm]

Please open a new detailed issue adding a Minimal, Reproducible Example.