Here’s how I was able to test out this change.

1. Create a file named kubernetes-port-test.nix
2. Put the following into that file:

   # 🅭🄍1.0 This file is dedicated to the public domain using the CC0 1.0 Universal
   # Public Domain Dedication:
   # <https://creativecommons.org/publicdomain/zero/1.0/>
   
   let
     configuration = {
       services.kubernetes.apiserver = {
         enable = true;
         advertiseAddress = "example.com";
         securePort = 1234;
       };
     };
     pkgs = import path/to/nixpkgs { };
     nixOSPackage = pkgs.nixos configuration;
   in nixOSPackage.config.services.kubernetes.apiserverAddress

3. Run nix-instantiate --eval kubernetes-port-test.nix

When I do that procedure with Nixpkgs’s master branch checked out, nix-instantiate prints "https://example.com". When I do that preocedure with this PR’s branch checked out, nix-instantiate prints "https://example.com:1234". In other words, I think that this PR works properly.

I also tried running the tests for the Kubernetes module. nix-build -A nixosTests.kubernetes.dns failed on my system, but that test also fails when I run it with this PR’s parent commit, so I don’t think that this PR needs to address that failure. nix-build -A nixosTests.kubernetes.rbac succeeded on my system.

Here’s what I think should be changed:

• The commit message should start with “nixos/kubernetes:” (See this section of nixos/README.md.)
• I would take the “Motivation for this change” section of the PR comment, and put it in the body of the commit message. That will make it easier for people to understand this change when using git-log.