add a new api to toggle empty folders

doc/nvim-tree-lua.txt

@@ -181,6 +181,7 @@ Show the mappings:  `g?`
 `I`               Toggle Filter: Git Ignore  |nvim-tree-api.tree.toggle_gitignore_filter()|
 `J`               Last Sibling               |nvim-tree-api.node.navigate.sibling.last()|
 `K`               First Sibling              |nvim-tree-api.node.navigate.sibling.first()|
+`L`               Group or Ungroup Folders   |nvim-tree-api.node.tree.toggle_grouped_folders()|
 `M`               Toggle Filter: No Bookmark |nvim-tree-api.tree.toggle_no_bookmark_filter()|
 `m`               Toggle Bookmark            |nvim-tree-api.marks.toggle()|
 `o`               Open                       |nvim-tree-api.node.open.edit()|
@@ -1848,6 +1849,9 @@ node.open.vertical()                      *nvim-tree-api.node.open.vertical()*
 node.open.horizontal()                  *nvim-tree-api.node.open.horizontal()*
     |nvim-tree-api.node.edit()|, file will be opened in a new horizontal split.
 
+node.open.toggle_grouped_folders()      *nvim-tree-api.node.open.toggle_grouped_folders()*
+    |nvim-tree-api.node.edit()|, empty folders would be grouped or ungrouped.
+
 node.open.drop()                              *nvim-tree-api.node.open.drop()*
     Switch to window with selected file if it exists.
     Open file otherwise.
@@ -2196,6 +2200,7 @@ You are encouraged to copy these to your own |nvim-tree.on_attach| function.
   vim.keymap.set('n', 'I',       api.tree.toggle_gitignore_filter,    opts('Toggle Filter: Git Ignore'))
   vim.keymap.set('n', 'J',       api.node.navigate.sibling.last,      opts('Last Sibling'))
   vim.keymap.set('n', 'K',       api.node.navigate.sibling.first,     opts('First Sibling'))
+  vim.keymap.set('n', 'L',       api.node.open.toggle_grouped_folders,opts('Toggle Grouped Folders'))
   vim.keymap.set('n', 'M',       api.tree.toggle_no_bookmark_filter,  opts('Toggle Filter: No Bookmark'))
   vim.keymap.set('n', 'm',       api.marks.toggle,                    opts('Toggle Bookmark'))
   vim.keymap.set('n', 'o',       api.node.open.edit,                  opts('Open'))

lua/nvim-tree/api.lua

@@ -175,12 +175,12 @@ end
 
 ---@param mode string
 ---@return fun(node: table)
-local function open_or_expand_or_dir_up(mode)
+local function open_or_expand_or_dir_up(mode, toggle_group)
   return function(node)
     if node.name == ".." then
       actions.root.change_dir.fn ".."
     elseif node.nodes then
-      lib.expand_or_collapse(node)
+      lib.expand_or_collapse(node, toggle_group)
     else
       edit(mode, node)
     end
@@ -195,6 +195,7 @@ Api.node.open.no_window_picker = wrap_node(open_or_expand_or_dir_up "edit_no_pic
 Api.node.open.vertical = wrap_node(open_or_expand_or_dir_up "vsplit")
 Api.node.open.horizontal = wrap_node(open_or_expand_or_dir_up "split")
 Api.node.open.tab = wrap_node(open_or_expand_or_dir_up "tabnew")
+Api.node.open.toggle_grouped_folders = wrap_node(open_or_expand_or_dir_up("toggle_grouped_folders", true))
 Api.node.open.preview = wrap_node(open_or_expand_or_dir_up "preview")
 Api.node.open.preview_no_picker = wrap_node(open_or_expand_or_dir_up "preview_no_picker")
 

lua/nvim-tree/keymap.lua

@@ -72,6 +72,7 @@ function M.default_on_attach(bufnr)
   vim.keymap.set('n', 'I',       api.tree.toggle_gitignore_filter,    opts('Toggle Filter: Git Ignore'))
   vim.keymap.set('n', 'J',       api.node.navigate.sibling.last,      opts('Last Sibling'))
   vim.keymap.set('n', 'K',       api.node.navigate.sibling.first,     opts('First Sibling'))
+  vim.keymap.set('n', 'L',       api.node.open.toggle_grouped_folders,opts('Toggle Grouped Folders'))
   vim.keymap.set('n', 'M',       api.tree.toggle_no_bookmark_filter,  opts('Toggle Filter: No Bookmark'))
   vim.keymap.set('n', 'm',       api.marks.toggle,                    opts('Toggle Bookmark'))
   vim.keymap.set('n', 'o',       api.node.open.edit,                  opts('Open'))

lua/nvim-tree/lib.lua

@@ -88,6 +88,7 @@ function M.get_last_group_node(node)
 end
 
 ---Group empty folders
+-- Recursively group nodes
 ---@param node Node
 ---@return Node[]
 function M.group_empty_folders(node)
@@ -102,7 +103,8 @@ function M.group_empty_folders(node)
   return node.nodes
 end
 
----Group empty folders
+---Ungroup empty folders
+-- If a node is grouped, ungroup it: put node.group_next to the node.nodes and set node.group_next to nil
 ---@param node Node
 function M.ungroup_empty_folders(node)
   local cur = node
@@ -125,8 +127,26 @@ function M.get_all_nodes_in_group(node)
   return nodes
 end
 
+-- If a folder is grouped and closed -> group folder and open
+-- If a folder is grouped and opened -> ungroup folder and open
+-- If a folder is ungrouped and opened -> group folder and close
+---@param head_node Node
+---@param open boolean
+---@return boolean
+local function toggle_group_folders(head_node, open)
+  local is_grouped = head_node.group_next ~= nil
+
+  if open and is_grouped then
+    M.ungroup_empty_folders(head_node)
+  elseif open then
+    M.group_empty_folders(head_node)
+  end
+  return is_grouped or not open
+end
+
 ---@param node Node
-function M.expand_or_collapse(node)
+function M.expand_or_collapse(node, toggle_group)
+  toggle_group = toggle_group or false
   if node.has_children then
     node.has_children = false
   end
@@ -135,17 +155,16 @@ function M.expand_or_collapse(node)
     core.get_explorer():expand(node)
   end
 
-  local open = M.get_last_group_node(node).open
   local head_node = utils.get_parent_of_group(node)
-  local is_grouped = head_node.group_next ~= nil
-
-  if open and is_grouped then
-    M.ungroup_empty_folders(head_node)
-  elseif open then
-    M.group_empty_folders(head_node)
+  local open = M.get_last_group_node(node).open
+  if toggle_group then
+    open = toggle_group_folders(head_node, open)
+  else
+    open = not open
   end
+
   for _, n in ipairs(M.get_all_nodes_in_group(head_node)) do
-    n.open = is_grouped or not open
+    n.open = open
   end
 
   renderer.draw()