VINYL formats yaml files into a canonical format retaining comments and setting the indentation by default to two spaces, including for sequences, e.g.:

# List of recipes
recipies:
  # todo
  - pizza: {}
  # todo
  - lasagna: {}
  - barley soup:
      ingredients:
        - barley
        - onions
        - beef
      serves: 4

It uses code from gofmt and go-yaml does the heavy lifting of parsing the yaml and formatting the output

$ ./vinyl --help
usage: vinyl [flags] [path ...]
  -cpuprofile string
        write cpu profile to this file
  -d    display diffs instead of rewriting files
  -i uint
        number of spaces to indent (default 2)
  -l    list files whose formatting differs from vinyl's
  -m    don't error on duplicate keys in mappings
  -w    write result to (source) file instead of stdout

Without an explicit path, it processes from standard input. Given a file, it operates on that file; given a directory, it operates on all .yaml and .yml files in that directory, recursively.

By default, vinyl prints the reformatted sources to standard output.

• yamlfmt: VINYL is a fork of yamlfmt
• gofmt: Code to format all files and handle errors
• go-yaml YAML parser