TL;DR:

• Write YAML as JSON5 (but use # for comments)
• Enforce this style with yaml5 lint

# JSON5? YAML?
{a: 1, b: ['x', 'y']}

What you see above is a valid YAML 1.2 document.
It uses the flow-style syntax for objects and arrays.

If you look at the JSON5 feature list, you can deduce that YAML is a superset of JSON5.
The only difference is the single-line comment syntax.

Yes, we can go and re-write all YAML files in a JSON5 style.

YAML5 is the “JSON with comments and trailing commas” that some of us were waiting for. Just take YAML and write it like JSON5, the yaml5 lint tool can enforce our promise of not using any features outside of the JSON5 subset:

$ cat bad.yaml
foo:
  - a
  - key: val

$ yaml5 lint bad.yaml 
bad.yaml:1:4: used a key-value outside of an object
bad.yaml:2:3: use a flow array syntax [] instead
bad.yaml:2:5: unquoted strings are not allowed
bad.yaml:3:8: used a key-value outside of an object
bad.yaml:3:10: infinity value should not be used

I’m planning to implement yaml5 fmt tool that would pretty-print a YAML document as YAML5 document.