Lua: more vim.iter functions

[justinmk]

Problem

vim.iter() was added in https://github.com/neovim/neovim/pull/23029 . This issue tracks related functions on there.

Related: vim.func https://github.com/neovim/neovim/issues/28449

Expected behavior

• ✅ reduce (Iter:fold())
• table management: https://github.com/neovim/neovim/issues/24572
  • clone
  • keys
  • values
  • get-in (get in nested tables)
  • ~get (as a safe alternative to direct referencing)~
    • Too trival, d and d[k] is idiomatic.

[theHamsta]

it1:chain(it2) would be nice.

[stasjok]

Maybe expose also ListIter.new? So that the programmer can bypass list check loop if he knows beforehand that his table is definitely a list. https://github.com/neovim/neovim/blob/558e4191f049662065984677a9c7cdbb1518092a/runtime/lua/vim/iter.lua#L781-L789

[justinmk]

expose also ListIter.new? So that the programmer can bypass list check loop if he knows beforehand that his table is definitely a list.

Could do this as kwargs (opt) parameter on vim.iter() itself. In general, we should probably use that pattern for all functions that accept a table/list/etc (while keep the common case low-verbosity).

[stasjok]

I now noticed that this loop creates a copy of the table. There probably was a reason for this. So it is unavoidable if we don't want to mutate user's table.

[zjykzk]

range(i, j) is fine