Convert JSON keys from camelCase to SNAKE_CASE

Today, I had to support syslog messages in two formats using a single mapping block:

1. JSON Format – where keys are in camelCase
2. Syslog Format – where keys are in SNAKE_CASE

To solve this, I came up with a Benthos preprocessor that converts camelCase keys to snake_case, then uppercases them. Here's the logic I used:

map camel_to_snake {
  root = this.re_replace_all("([a-z])([A-Z])", "${1}_${2}").lowercase()
}

root = this.map_each_key(ele -> ele.apply("camel_to_snake")).uppercase()

Input

{
  "actionName": "allowed",
  "computerName": "test.example.com",
  "destinationIp": "127.0.0.1"
}

Output

{
  "ACTION_NAME": "allowed",
  "COMPUTER_NAME": "test.example.com",
  "DESTINATION_IP": "127.0.0.1"
}