[BUG] - cardano-node shows misleading error when using strings for port/valency in topology.json

[rcmorano]

Internal/Exernal

External

Summary

If you happen to format your topology.json using strings instead of integers for peers' port or valency (or both :), you end up receiving this misleading error saying something is empty:
{fatalErrorMessage = "Cardano.Node.Run.readTopologyFile: Error in $: empty"}

This problem has led some people to walk around in circles for hours.

Steps to reproduce

See screenshots/attachments.

Expected behavior

cardano-node should cast these values to integer or report some non-misleading message.

System info (please complete the following information):

• OS: Ubuntu
• Version: 20.04
• Node version: binary build from hydra:

root@passive-node-0:/# cardano-node --version
cardano-node 1.15.1 - linux-x86_64 - ghc-8.6
git rev 712a287602797e8fd889fbf73e56a08c3d8b004a
root@passive-node-0:/# 

Screenshots and attachments

root@passive-node-0:/# cat /opt/cardano/cnode/files/topology.json.bad
{
  "Producers": [
    {
      "addr": "relays-new.mainnet-candidate.dev.cardano.org",
      "port": "3001",
      "valency": 3
    }
  ]
}
root@passive-node-0:/# cardano-node run --config /opt/cardano/cnode/files/configuration.yaml --database-path /opt/cardano/cnode/db --host-addr 0.0.0.0 --port 31111 --topology /opt/cardano/cnode/files/topology.json.bad; echo
{"at":"2020-07-13T17:28:08.63Z","env":"1.15.1:712a2","ns":["cardano.#ekgview.realizeFrom"],"data":{"kind":"LogError","message":"EKGView backend disabled due to initialisation error: EKGServerStartupError \"Network.Socket.bind: resource busy (Address in use)\""},"app":[],"msg":"","pid":"120","loc":null,"host":"","sev":"Error","thread":"5"}

cardano-node: FatalError {fatalErrorMessage = "Cardano.Node.Run.readTopologyFile: Error in $: empty"}
root@passive-node-0:/# 

Additional context

Removing quotes from the topology so port/valency is taken as an integer fixes the problem.