YAML file requires different amounts of indentation for different nodes

I'm attempting to write a YAML config script for a load testing utility called Artillery.

The YAML syntax is not making any sense to me though. Artillery appears to deserialize the YAML to a Javascript object syntax so it expects nodes in the YAML file to have a certain structure.

config:
  target: https://mhhs-prod-webapp.azurewebsites.net/
  phases:
    - duration: 60
      arrivalRate: 50
scenarios:
  - flow:
    - get:
      url: '/'

Given the above file though it fails complaining that 'get' must be of type object. In the file above the get node has a child node url of key value type, so I'm expecting it to be of type object.

After much trial and error I've managed to get it to work using the following layout.

config:
  target: https://mhhs-prod-webapp.azurewebsites.net/
  phases:
    - duration: 60
      arrivalRate: 50
scenarios:
  - flow:
    - get:
        url: '/'

But the bizarre thing is that this file is identical to the previous one apart from the fact that the url node is indented 4 spaces instead of the 2 spaces of indentation used throughout the rest of the file.

Is this correct? I'm having trouble finding an explanation of YAML that is understandable but so far I haven't come across anything that suggests that different amounts of indentation do completely different things.

Solution

Hohoho, I understand how you feel about YAML indentations.

It's like Python-based indentation but with a mix of JSON.

In your code:

  config:
    ...
  scenarios:
    - flow:
      - get:
        url: '/'

"url" looks like a child of "flow" since it has an indent like so.

It can go in a couple of routes.

Route #1: (Where "url" is under "flow:")

  ...
  scenarios:
    - flow:
      - get:
      - url: '/'

Route #2: (Where "url" is under "get:")

  ...
  scenarios:
    - flow:
      - get:
        - url: '/'

Route #3: (Where "url" is under~ uhm...)

  config:
    ...
  scenarios:
    ...
  url: '/'