YAML indentation for array in hash

Question

I think indentation is important in YAML.

I tested the following in irb:

> puts({1=>[1,2,3]}.to_yaml) ---  1:  - 1 - 2 - 3  => nil  

I expected something like this:

> puts({1=>[1,2,3]}.to_yaml) ---  1:    - 1   - 2   - 3  => nil  

Why isn't there indentation for the array?

I found this at http://www.yaml.org/YAML_for_ruby.html#collections.

The dash in a sequence counts as indentation, so you can add a sequence inside of a mapping without needing spaces as indentation.

Answer 1

Both ways are valid, as far as I can tell:

require 'yaml'  YAML.load(%q{---  1: - 1 - 2 - 3 }) # => {1=>[1, 2, 3]}  YAML.load(%q{---  1:   - 1   - 2   - 3 }) # => {1=>[1, 2, 3]} 

It's not clear why you think there should be spaces before the hyphens. If you think this is a violation of the spec, please explain how.

Why isn't there indentation for the array?

There's no need for indentation before the hyphens, and it's simpler not to add any.

Answer 2

It's so you can do:

1:  - 2: 3   4: 5 - 6: 7   8: 9 - 10 => {1 => [{2 => 3, 4 => 5}, {6 => 7, 8 => 9}, 10]} 

Basically, dashes delimit objects, and indentation denotes the "value" of the key-value pair.

That's the best I can do; I haven't managed to find any of the reasons behind this or that aspect of the syntax.