fix: filter out duplicate dns results MONGOSH-2027

[nirinchev]

This appears to be the cause of the failures we're seeing in mongosh. The logs indicate that we're getting duplicate dns addresses, which causes us to fire up two servers, one of which will inevitably fail due to address being in use. Here's the corresponding log message:

2025-02-26T17:22:33.225Z connection controller INFO  OIDC-PLUGIN [
  { __value: 1002000028 },
  'compass-oidc',
  'Resolved hostnames for local server',
  {
    url: 'http://localhost:37197/redirect',
    urlPort: 37197,
    hostname: 'localhost',
    interfaces: [
      { address: '127.0.0.1', family: 4 },
      { address: '127.0.0.1', family: 4 }
    ]
  }
]

[addaleax]

Code LGTM but this should have a ticket number before merging and an associated spec change

[addaleax]

optional suggestions: Feels a bit silly to mark this private and then access it as if it weren't private, no? It's not exported from the package anyway, don't be shy to mark this public to make it a bit more obvious that it's tested directly

And while you're at it, you might as well pass in dns.lookup as an argument instead of mocking it in that case?

[nirinchev]

I was debating with myself whether I want to make it public or if I want to instead call .listen() and then inspect the logs to see what interfaces were discovered. I feel a bit iffy about exposing methods publicly only for the sake of testing, but perhaps that's a bit more acceptable in the JS world 😅

[addaleax]

If that feels iffy, I think you could also just export it as a separate method, it's fairly standalone and not really tied to the rest of the class semantically 🙂