feat(lsp): support `textDocument/foldingRange` (#31311)

* refactor(shared): extract `vim._list_insert` and `vim._list_remove`

* feat(lsp): add `vim.lsp.foldexpr()`

* docs(lsp): add a todo for state management

* feat(lsp): add `vim.lsp.folding_range.foldclose()`

* feat(lsp): schedule `foldclose()` if the buffer is not up-to-date

* feat(lsp): add `vim.lsp.foldtext()`

* feat(lsp): support multiple folding range providers

* refactor(lsp): expose all folding related functions under `vim.lsp.*`

* perf(lsp): add `lsp.MultiHandler` for do `foldupdate()` only once

1 files changed, 4 insertions, 49 deletions

diff --git a/runtime/lua/vim/treesitter/_fold.lua b/runtime/lua/vim/treesitter/_fold.lua
index 7237d2e7d4..0cb5b497c7 100644
--- a/runtime/lua/vim/treesitter/_fold.lua
+++ b/runtime/lua/vim/treesitter/_fold.lua
@@ -30,65 +30,20 @@ function FoldInfo.new()
   }, FoldInfo)
 end
 
---- Efficiently remove items from middle of a list a list.
----
---- Calling table.remove() in a loop will re-index the tail of the table on
---- every iteration, instead this function will re-index  the table exactly
---- once.
----
---- Based on https://stackoverflow.com/questions/12394841/safely-remove-items-from-an-array-table-while-iterating/53038524#53038524
----
----@param t any[]
----@param first integer
----@param last integer
-local function list_remove(t, first, last)
-  local n = #t
-  for i = 0, n - first do
-    t[first + i] = t[last + 1 + i]
-    t[last + 1 + i] = nil
-  end
-end
-
 ---@package
 ---@param srow integer
 ---@param erow integer 0-indexed, exclusive
 function FoldInfo:remove_range(srow, erow)
-  list_remove(self.levels, srow + 1, erow)
-  list_remove(self.levels0, srow + 1, erow)
-end
-
---- Efficiently insert items into the middle of a list.
----
---- Calling table.insert() in a loop will re-index the tail of the table on
---- every iteration, instead this function will re-index  the table exactly
---- once.
----
---- Based on https://stackoverflow.com/questions/12394841/safely-remove-items-from-an-array-table-while-iterating/53038524#53038524
----
----@param t any[]
----@param first integer
----@param last integer
----@param v any
-local function list_insert(t, first, last, v)
-  local n = #t
-
-  -- Shift table forward
-  for i = n - first, 0, -1 do
-    t[last + 1 + i] = t[first + i]
-  end
-
-  -- Fill in new values
-  for i = first, last do
-    t[i] = v
-  end
+  vim._list_remove(self.levels, srow + 1, erow)
+  vim._list_remove(self.levels0, srow + 1, erow)
 end
 
 ---@package
 ---@param srow integer
 ---@param erow integer 0-indexed, exclusive
 function FoldInfo:add_range(srow, erow)
-  list_insert(self.levels, srow + 1, erow, -1)
-  list_insert(self.levels0, srow + 1, erow, -1)
+  vim._list_insert(self.levels, srow + 1, erow, -1)
+  vim._list_insert(self.levels0, srow + 1, erow, -1)
 end
 
 ---@param range Range2