This is an issue with Ruby's YAML implementation. YAML 1.2 processors should interpret documents without YAML directive as if they were YAML 1.2 documents - see https://yaml.org/spec/1.2.2/#681-yaml-directives.
See the last section -- a parser that interprets YAML as v1.2 by default will break for YAML v1.1 documents.
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.
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.