Commas seem optional in flow sequences - is this intended?

We noticed that:

new YamlReader("['a'b]").read();

would parse without error, returning a list with 2 strings, "a" and "b".

Other parsers (pyyaml, SnakeYAML) fail on parsing this, due to expecting a comma between entries.

This YAML specification https://yaml.org/spec/1.2.2/#flow-sequences states:

Flow sequence content is denoted by surrounding “[” and “]” characters.
...
Sequence entries are separated by a “,” character.

I found it surpising that this library allowed it and thought it worth an issue for discussion.

Running a few more tests, it doesn't seem to always work - so I expect allowing the above is a subtle bug. e.g.

        System.err.println(new YamlReader("['a'b]").read());
        System.err.println(new YamlReader("[a b c d]").read());
        System.err.println(new YamlReader("['a,b' c d]").read());
        System.err.println(new YamlReader("['a'b'c'd]").read());

outputs the following:

[a, b]
[a b c d]
[a,b, c d]
[a, b'c'd]

[NathanSweet]

I don't remember if that was done purposefully. In my other project, JsonBeans, I made commas optional purposefully. For YamlBeans it could be bug a or a feature, depending on perspective.

TBH the entire YAML format is a pretty big mess. I stopped using it in my projects.

In your 4 examples it appears to behave reasonably: delimiting a value with quotes separates it from subsequent values. If we can't find a scenario where the behavior is problematic, I'm inclined to leave it.

Thanks for responding.

It's not a big deal for us - we only noticed as GitHub was warning us about 2 vulns in this library (GHSA-jm7r-4pg6-gf26 and GHSA-vj49-j7rc-h54f), and as we migrated away from it to another library that was already in our stack, we found a couple of unit-tests in our code that began failing with the new library. When we investigated we found it was due to us inadvertently using invalid YAML in our unit-test, that this library allowed.

Since it seemed against the spec (and all other parsers I'd seen) and that we'd already spent the time investigating I thought I'd drop a drive-by issue - but we don't feel strongly about whether you change the behaviour or not.