fix(ast): preserve emptyline before comment

[hleb-rubanau]

Now AST converter tracks emptyline sequences in the source,
and emits a single emptyline into result
whenever such a sequence precedes the comment preceding the node

(NOTE: initial version of this PR was ditched and it was redone from scratch)

[hleb-rubanau]

@aldum I've completely changed the PR logic to the cleaner and more predictable approach.
Diff is fully replaced, so re-review is needed.

Apologies for the inconvenience!

[aldum]

I feel no confidence that I can game all of this out in my head, please add unit tests that demonstrate this code working as intended.

[aldum]

Can we be more specific about this type? If it's not some existing class, at least a structural type alias would be useful.

[hleb-rubanau]

I would ask for your help/recommendation here then.

In practice it's ad-hoc polymorphic, accepting a union of two types.

Annotation problem is that one of them is not defined explicitl, and for another one I just cannot find type definition within sane time:

1. clast table as built on line 402 simply does not have type definition or alias
2. node.lineinfo.first or node.lineinfo.last could be passed -- but I am not sure where the type is defined

[aldum]

lineinfo is defined here in turn referencing position here
clast is a value, it's type is basically Cursor, but that's in compy, so metalua strictly speaking doesn't know about it.
An ad-hoc union works here, as in

---- @param pos position|{l : integer}

Long term, probably this should be refactored to use a position type, or a new PositionBase (equivalent to Cursor). There's some impedance mismatch because metalua originally had nothing for types (this language server we use might have not even existed yet).

[hleb-rubanau]

Done, please check

[hleb-rubanau]

I feel no confidence that I can game all of this out in my head, please add unit tests that demonstrate this code working as intended.

Just added and pushed (see last commit), would love to know your thoughts

[aldum]

one more nit: autoformat

[hleb-rubanau]

Done, for this file only (several other changed, such as ast_to_src itself and spec examples, I did not risk lintering, as they seem to purposefully ignore double-quoting standard for the sake of clarity, and maybe few other conventions too).

For convenience, I've added also added .editorconfig and justfile lint directive (using stylua just because why not). I do not insist them to be a freezed canon, rather some reasonable baseline to start from.