Expose the Dumper and Parser objects publicly / allow overriding of methods in options

[kikito]

On my investigation towards generating a yaml with sorted keys (#45), I realized that I need is the Dumper object used in lyaml/init.lua with a small tweak to the dump_mapping function.

It seems that the only way for me to accomplish this would be to copy-paste the whole implementation of dumper_mt.

I realize that this might be a philosophical point about design, but this feels "wrong" to me.

I see two approaches that would make this less painful:

• Option a) Exposing Dumper and Parser directly in the lyaml library

local Dumper = require('lyaml').Dumper`)

Then I would be able to build/customize my custom dumper file easily.

This would be trivial to implement, but perhaps a bit "crude". It also opens the door for global modifications of the library (someone could decide to monkeypatch the global Dumper object, instead of using it to build a new Dumper object and using that).

• Option b) Allowing overriding specific dumper methods via the options parameter

local str = lyaml.dump(tbl, { dump_mapping = my_custom_dump_mapping })

I... honestly don't see a lot of big drawbacks to this one. It seems simple to implement and can be done without exposing global variables for modification.

Would you be open to accepting a PR on any of these directions?

[gvvaughan]

Sure, the second seems like a good approach, I’d be happy to merge a PR for that :-)