Support for reading comments

[mmeroberts]

SnakeYaml has an option to process comments. It would be good to be able to have access to that option from clj, ideally from bb as well.

See https://github.com/snakeyaml/snakeyaml/blob/master/src/main/java/org/yaml/snakeyaml/LoaderOptions.java

private boolean processComments = false;

My use case is to parse yaml documents that are very heavily commented as they main audience is human.

I am raising the issue first and could explore having a go at adding it, but following instructions from the Developer docs, it suggests raising issue first.

[borkdude]

OK, PR welcome to see what can be done about it. Please also add a test :)

[mmeroberts]

I have played around with the options - something is happening - for example when parsing the list-yaml in the tests I get a exception as there is an open issue in Snake yaml for a comment in that position. What I found is that setting the option does not change the output at all. There is a line in one of the snakeyaml files that says:
while (scanner.checkToken(Token.ID.Comment)) { // TODO: till we figure out what todo with the comments scanner.getToken(); }

Which does not give me any confidence that the comments will end up somewhere. There is also an old issue where the devs just say that the comment is over-ridden by the node that comes next.

Shame. Would appreciate someone else confirming this.

[asomov]

@mmeroberts thank you very much for the contribution. The mentioned TODO was removed as non applicable any longer.
For your information. The parsing/dumping comments in SnakeYAML is fully functional.