¬ just serendipity 🍀 (not just serendipity)

I needed to translate the following shell command (bash):

instance="thiago-perrotta"
kubectl get secret -n "c-$instance" "$instance-factory" -o jsonpath='{.data.conf\.json}' | base64 --decode | jq --arg url 'rabbitmq.url' -r '.[$url]'

…to Ruby. It reads a JSON entry from a kubernetes secret and extracts a specific key from it with jq.

I wrote a helper function to do so:

def factory_conf_json_rabbitmq_url
  # amqp://{user}:{password}@{host}:{port}
  Helpers::LocalShell.capture_without_error(
    "kubectl get secret -n c-#{@target.name} #{@target.name}-factory -o jsonpath='{.data.conf\.json}' | base64 --decode | jq --arg url 'rabbitmq.url' -r '.[$url]'"
  )&.strip&.split('@')&.last&.split(':')&.first
end

It took me a long time to figure out what was wrong with that code. It was returning an empty string.

It turns out it was a very simple issue: string escaping!

One must do {.data.conf\\.json}. The backslash needs to be escaped.

How did I figure it out? Heck, I didn’t. I just asked ChatGPT how to translate the shell expression above into Ruby, and it has correctly emitted the escaped string in Ruby.

In hindsight, the error is quite obvious. Isn’t it always like that?¹.