Any reason for the following behavior?

[ashmaroli]

Given the following Ruby script:

require 'yaml'
puts YAML::VERSION

text = <<~TXT
  items:
    tags:
      - 0001
      - 0002
      - 0003
      - 0004
      - 0005
      - 0006
      - 0007
      - 0008
      - 0009
TXT

puts YAML.dump YAML.load(text)

when run outputs the following:

3.3.0
---
items:
  tags:
  - 1
  - 2
  - 3
  - 4
  - 5
  - 6
  - 7
  - '0008'
  - '0009'

Any reason why there's a special behavior for numbers 0-7 but not for 8 and 9?

[perlpunk]

ruby psych implements YAML 1.1. https://perlpunk.github.io/yaml-test-schema/schemas.html
0001 - 0007 are read as octal numbers. 0008 and 0009 can't be octal, so they are resolved as a string. When dumping again, I guess they are quoted to make clear that they are strings, but the quotes wouldn't be strictly required.