refactor(lua): deprecate tbl_flatten

Problem:
Besides being redundant with vim.iter():flatten(), `tbl_flatten` has
these problems:

- Has `tbl_` prefix but only accepts lists.
- Discards some results! Compare the following:
  - iter.flatten():
    ```
    vim.iter({1, { { a = 2 } }, { 3 } }):flatten():totable()
    ```
  - tbl_flatten:
    ```
    vim.tbl_flatten({1, { { a = 2 } }, { 3 } })
    ```

Solution:
Deprecate tbl_flatten.

Note:
iter:flatten() currently fails ("flatten() requires a list-like table")
on this code from gen_lsp.lua:

    local anonym = vim.iter({ -- remove nil
      anonymous_num > 1 and '' or nil,
      '---@class ' .. anonymous_classname,
    }):flatten():totable()

Should we enhance :flatten() to work for arrays?

1 files changed, 1 insertions, 1 deletions

diff --git a/runtime/lua/vim/lsp/handlers.lua b/runtime/lua/vim/lsp/handlers.lua
index d6579cf4b3..4672d94105 100644
--- a/runtime/lua/vim/lsp/handlers.lua
+++ b/runtime/lua/vim/lsp/handlers.lua
@@ -12,7 +12,7 @@ local M = {}
 --- Writes to error buffer.
 ---@param ... string Will be concatenated before being written
 local function err_message(...)
-  vim.notify(table.concat(vim.tbl_flatten({ ... })), vim.log.levels.ERROR)
+  vim.notify(table.concat(vim.iter({ ... }):flatten():totable()), vim.log.levels.ERROR)
   api.nvim_command('redraw')
 end