Fix hasSubscribers when channel only has bindStore subscriptions in node <=20

[uurien]

Using Node.js diagnostics_channel, this code returns true:

const diagnostics_channel = require('node:diagnostics_channel');
// const diagnostics_channel = require('dc-polyfill')
const channel = diagnostics_channel.channel('my-channel');
const store = {}

channel.bindStore(store, () => {});

console.log('channel.hasSubscribers', channel.hasSubscribers)

But if node:diagnostics_channel is replaced by dc-polyfill, it returns false in node 18.

This PR want to fix that.

[tlhunter]

For the test-*.spec.js files we basically copy and paste from the Node.js repository, make a few changes to be compatible with the test runner, and then commit that. In theory it will help us backport more tests in the future. But for tests that Node.js probably doesn't care about and we do, we then add a completely new test file to the test/ dir that doesn't have a test-* prefix.

For example this test file is copied from Node here:
https://github.com/nodejs/node/blob/main/test/parallel/test-diagnostics-channel-has-subscribers.js

Instead of adding the new test cases to this Node.js file can you make an entirely new test file?

[simon-id]

is your PR taking inspiration from node core ? since this looks like it was fixed in node core, we should copy that change, and the test that goes with it

[uurien]

is your PR taking inspiration from node core ? since this looks like it was fixed in node core, we should copy that change, and the test that goes with it

node core code for stores is very different, it doesn't need to add support to existing channel, so it works replacing the prototype when a store or subscription is added. Here we are not doing that for stores.

[simon-id]

feel free to wait for thomas approval too

[uurien]

feel free to wait for thomas approval too

Yes, definitely I'll wait for him