My YAML secret weapon is that JSON is more or less valid YAML. So, if you want YAML with a “safer syntax”, just write JSON instead. You can sprinkle in comments if needed.
Don't use YAML 1.1
If you force 1.2 without the header I suppose it works, but breaks compatibility?
YAML spec is a huge with bunch of gotchas. E.g. C# has two listed parsers. One is 1.2 compatible and unmaintained.
Don't use YAML 1.2, use the secure subset 1.1. Or even better StrictYAML
I mean, things like "NO" were fixed later.
StrictYAML got rid of all these, as all the safer YAML variants. E.g. perl5 still uses 1.0 for its cpan metadata abstraction, and still has to restrict these. I maintain the https://metacpan.org/pod/YAML::Safe module, which allows whitelisting of certain objects.
There's no way to determine whether a `.yaml` file is YAML v1.1 or v1.2 without a version directive, and most YAML documents are v1.1 because most YAML parsers default to v1.1 semantics.
I used Ruby as an example since it's easily available on most platforms, but you could also use Python or C++ or Swift or whatever language[1] you prefer. The underlying issue -- YAML not being a subset of JSON -- is universal.
[1] Note that some libraries, such as go-yaml, do their own thing and don't conform to either v1.1 or v1.2 semantics.