Add comments when dumping

[solaluset]

I thought it'd be useful to have a possibility to add comments when dumping by passing comments=... to dump(s). Also I've added trailing_comma arg that adds trailing commas everywhere.

[n-takumasa]

Thanks for the suggestion.

What is your intended use-case?
Considering symmetry, load should add a function to get comments.
But I think comments are not data.

[solaluset]

Exactly, comments are not data. That's why I think it shouldn't be possible to extract them. But adding them is a different thing. My program generates a config file and I want the user to see what is the meaning of some settings. You can see the code here:

https://github.com/Krutyi-4el/DandelionMusic/blob/44e34d1ce23709f6214a6d5ea3d5ff402d27078c/config/config.py#L176

[n-takumasa]

request changes:

• add annotations for _get_comments
• add error handling when any inconsistencies occur with data and comments

[n-takumasa]

I see your intent, I thin it's fine for that use-case.
However, I have made some requests to improve robustness, please consider them.

[solaluset]

add error handling when any inconsistencies occur with data and comments

Not sure about this one. Should the script validate that all keys in dictionary are strs when commenting dict and ints when list?

[n-takumasa]

add error handling when any inconsistencies occur with data and comments

Not sure about this one. Should the script validate that all keys in dictionary are strs when commenting dict and ints when list?

I think that at least occurence a warning will help.

print(jsonc.dumps({"b": 1}, indent=2, comments={"a": "foo"}))
# {
#   "b": 1
# }

Also, when you give comments arg with no indent arg, a warning should be occur.

[solaluset]

I've added warns for unused comment keys. However, it has a side effect of removing all used ones from original dictionary. I'll add copy.deepcopy() if you think it may become an issue.

[n-takumasa]

Nice work

deepcopy is necessary because I usually think that functions must not have any side effect on their arguments.

[n-takumasa]

merged. thanks!