Improve Cross-environment portability of libp2p core

[maschad]

#2110 raised an issue about the portability of js-libp2p's core modules, js bundlers are going away anytime soon, and so consumers may run into these issues again depending on their configurations. As @wemeetagain suggested to avoid the hassle of bundlers, whilst making libp2p truly portable, we should:

a) stay away from modules which are not cross-environment.

b) if we do need to use a module that is environment specific, we should at least conditionally import it and/or return a no-op for the inapplicable environment.

[wemeetagain]

Would like to add a specific actionable result or subissue:

• ability to consume libp2p from browser without a bundler

[achingbrain]

I'd like this too, however it would require removing all CJS code from our stack - there are still a whole bunch of dependencies we have that are not ESM.

[wemeetagain]

we should list and kill one by one, there can't be too many left

[achingbrain]

It's a bunch of the older modules - node-forge springs instantly to mind, also multicast-dns etc

[wemeetagain]

Copying my comment from #2134

---

I would like to see js-libp2p not require a bundler at all in order to consume in the browser. Related to our portability initiative.

I think that js-libp2p core should be as portable as possible, and that means using isomorphic, or at least portable code throughout.

Also this case, specifically, feels a bit silly. We're requiring browser consumers to bundle an events polyfill for a nodejs-specific feature (using setMaxListeners to avoid a warning) with no benefit to the browser consumer.

[achingbrain]

Completely agree with the above.

Since we smother any errors encountered when increasing the number of listeners, we could have solved this by adding "events": false to the "browser" field in package.json, but then we have to put up with lots of warnings on build:

▲ [WARNING] Import "setMaxListeners" will always be undefined because the file "(disabled):../../node_modules/events/events.js" has no exports [import-is-undefined]

    dist/src/connection-manager/utils.js:1:9:
      1 │ import { setMaxListeners } from 'events';

"events": {} instead yields one warning of:

▲ [WARNING] Each "browser" mapping must be a string or a boolean [package.json]

    package.json:201:14:
      201 │     "events": {}
          ╵               ^

..which sounds bad but the tests pass 🤷

Though previously we wanted to get rid of the try/catch because setMaxListeners is in all supported node versions now but we can't have both.

[wemeetagain]

Can we move the complexity to @libp2p/interface / @libp2p/interface/events?

eg:

// in packages/interface/package.json

"browser": { "events": {} },

// in packages/interface/src/events.ts

import { setMaxListeners as nodeSetMaxListeners } from 'events'
export function setMaxListeners(...) {
  try {
    nodeSetMaxListeners(...)
  } catch (e) {
    // swallow errors, gulp
  }
}

// in packages/libp2p and beyond

import {setMaxListeners} from '@libp2p/interface/events'

...
setMaxListeners(...)

[achingbrain]

Yes, that'd be an improvement.

I think we should also verify where this is still necessary. The classic one was while dialling - if a node had more than 10x addresses we'd have an abort signal with more than 10x listeners. Since smart-dialling we only dial one address at a time now so we might not trigger the warning.

The DHT increases the number of listeners on the query abort signals but the queries involve a lot of dialling, but we've calmed the dialling down so it may be removable too.