question about the yaml sequences indent

[chenzhiwei]

When marshal from an object, this library will generate sequences in following format:

--- m dump:
a: Easy!
b:
  c: 2
  d:
  - 3
  - 4

But according to yaml spec: https://yaml.org/spec/1.2/#id2797382

The format seems to be:

--- m dump:
a: Easy!
b:
  c: 2
  d:
    - 3
    - 4

Is there any background on this?

[perlpunk]

Both are valid, and you will also find examples like your first in the spec.
Quote under https://yaml.org/spec/1.2/#id2799181 :

Since people perceive the “-” indicator as indentation, nested block sequences may be indented by one less space to compensate

[chenzhiwei]

Yes, both are valid.

I found some communities prefer the indented style.

https://developers.home-assistant.io/docs/documenting/yaml-style-guide/#block-style-sequences

https://github.com/flathub/flathub/wiki/YAML-Style-Guide

[robin-wayve]

The latest YAML spec does seem to give the un-indented as its canonical example (though it used to be indented): https://yaml.org/spec/1.2.2/#21-collections

[seh]

See my google/yamlfmt#87 (comment) in google/yamlfmt#87 for more detail on the specification's allowance for both styles.