refactor(#2886): multi instance: node group functions refactoring (#2959)

* move last_group_node to DirectoryNode

* move add BaseNode:as and more doc

* revert parameter name changes

* revert parameter name changes

* add Class

* move group methods into DN

* tidy group methods

* tidy group methods

* tidy group methods

* tidy group methods

* parent is DirectoryNode

* tidy expand all

* BaseNode -> Node

* move watcher to DirectoryNode

* last_group_node is DirectoryNode only

* simplify create-file

* simplify parent

* simplify collapse-all

* simplify live-filter

* style

lua/nvim-tree.lua

@@ -125,7 +125,7 @@ function M.place_cursor_on_node()
   if not node or node.name == ".." then
     return
   end
-  node = node:get_parent_of_group()
+  node = node:get_parent_of_group() or node
 
   local line = vim.api.nvim_get_current_line()
   local cursor = vim.api.nvim_win_get_cursor(0)

lua/nvim-tree/actions/finders/find-file.lua

@@ -43,6 +43,7 @@ function M.fn(path)
       return node.absolute_path == path_real or node.link_to == path_real
     end)
     :applier(function(node)
+      ---@cast node DirectoryNode
       local incremented_line = false
       if not node.group_next then
         line = line + 1

lua/nvim-tree/actions/fs/clipboard.lua

@@ -7,6 +7,8 @@ local notify = require("nvim-tree.notify")
 
 local find_file = require("nvim-tree.actions.finders.find-file").fn
 
+local DirectoryNode = require("nvim-tree.node.directory")
+
 ---@enum ACTION
 local ACTION = {
   copy = "copy",
@@ -219,7 +221,7 @@ end
 function Clipboard:do_paste(node, action, action_fn)
   if node.name == ".." then
     node = self.explorer
-  else
+  elseif node:is(DirectoryNode) then
     node = node:last_group_node()
   end
   local clip = self.data[action]

lua/nvim-tree/actions/fs/create-file.lua

@@ -5,6 +5,9 @@ local notify = require("nvim-tree.notify")
 
 local find_file = require("nvim-tree.actions.finders.find-file").fn
 
+local FileNode = require("nvim-tree.node.file")
+local DirectoryNode = require("nvim-tree.node.directory")
+
 local M = {}
 
 ---@param file string
@@ -29,35 +32,21 @@ local function get_num_nodes(iter)
   return i
 end
 
----@param node Node
----@return string
-local function get_containing_folder(node)
-  if node.nodes ~= nil then
-    return utils.path_add_trailing(node.absolute_path)
-  end
-  local node_name_size = #(node.name or "")
-  return node.absolute_path:sub(0, -node_name_size - 1)
-end
-
 ---@param node Node?
 function M.fn(node)
-  local cwd = core.get_cwd()
-  if cwd == nil then
+  node = node or core.get_explorer() --[[@as Node]]
+  if not node then
     return
   end
 
-  if not node or node.name == ".." then
-    node = {
-      absolute_path = cwd,
-      name = "",
-      nodes = core.get_explorer().nodes,
-      open = true,
-    }
-  else
-    node = node:last_group_node()
+  local dir = node:is(FileNode) and node.parent or node:as(DirectoryNode)
+  if not dir then
+    return
   end
 
-  local containing_folder = get_containing_folder(node)
+  dir = dir:last_group_node()
+
+  local containing_folder = utils.path_add_trailing(dir.absolute_path)
 
   local input_opts = {
     prompt = "Create file ",

lua/nvim-tree/actions/fs/rename-file.lua

@@ -6,6 +6,8 @@ local notify = require("nvim-tree.notify")
 
 local find_file = require("nvim-tree.actions.finders.find-file").fn
 
+local DirectoryNode = require("nvim-tree.node.directory")
+
 local M = {
   config = {},
 }
@@ -120,7 +122,9 @@ function M.fn(default_modifier)
       return
     end
 
-    node = node:last_group_node()
+    if node:is(DirectoryNode) then
+      node = node:last_group_node()
+    end
     if node.name == ".." then
       return
     end

lua/nvim-tree/actions/moves/item.lua

@@ -78,7 +78,7 @@ local function expand_node(node)
     ---@cast node DirectoryNode
     -- Expand the node.
     -- Should never collapse since we checked open.
-    node:expand_or_collapse()
+    node:expand_or_collapse(false)
   end
 end
 
@@ -102,7 +102,7 @@ local function move_next_recursive(what, skip_gitignored)
   end
   if node_init:is(DirectoryNode) and valid and not node_init.open then
     ---@cast node_init DirectoryNode
-    node_init:expand_or_collapse()
+    node_init:expand_or_collapse(false)
   end
 
   move("next", what, skip_gitignored)

lua/nvim-tree/actions/moves/parent.lua

@@ -1,6 +1,7 @@
 local view = require("nvim-tree.view")
 local utils = require("nvim-tree.utils")
-local core = require("nvim-tree.core")
+
+local DirectoryNode = require("nvim-tree.node.directory")
 
 local M = {}
 
@@ -9,33 +10,32 @@ local M = {}
 function M.fn(should_close)
   should_close = should_close or false
 
+  ---@param node Node
   return function(node)
-    local explorer = core.get_explorer()
-    node = node:last_group_node()
-    if should_close and node.open then
-      node.open = false
-      if explorer then
-        explorer.renderer:draw()
+    local dir = node:as(DirectoryNode)
+    if dir then
+      dir = dir:last_group_node()
+      if should_close and dir.open then
+        dir.open = false
+        dir.explorer.renderer:draw()
+        return
       end
-      return
     end
 
-    local parent = node:get_parent_of_group().parent
+    local parent = (node:get_parent_of_group() or node).parent
 
     if not parent or not parent.parent then
       return view.set_cursor({ 1, 0 })
     end
 
-    local _, line = utils.find_node(core.get_explorer().nodes, function(n)
+    local _, line = utils.find_node(parent.explorer.nodes, function(n)
       return n.absolute_path == parent.absolute_path
     end)
 
     view.set_cursor({ line + 1, 0 })
     if should_close then
       parent.open = false
-      if explorer then
-        explorer.renderer:draw()
-      end
+      parent.explorer.renderer:draw()
     end
   end
 end

lua/nvim-tree/actions/tree/modifiers/collapse-all.lua

@@ -3,6 +3,8 @@ local core = require("nvim-tree.core")
 local lib = require("nvim-tree.lib")
 local Iterator = require("nvim-tree.iterators.node-iterator")
 
+local DirectoryNode = require("nvim-tree.node.directory")
+
 local M = {}
 
 ---@return fun(path: string): boolean
@@ -36,8 +38,9 @@ function M.fn(keep_buffers)
   Iterator.builder(explorer.nodes)
     :hidden()
     :applier(function(n)
-      if n.nodes ~= nil then
-        n.open = keep_buffers == true and matches(n.absolute_path)
+      local dir = n:as(DirectoryNode)
+      if dir then
+        dir.open = keep_buffers and matches(dir.absolute_path)
       end
     end)
     :recursor(function(n)

lua/nvim-tree/actions/tree/modifiers/expand-all.lua

@@ -2,6 +2,8 @@ local core = require("nvim-tree.core")
 local Iterator = require("nvim-tree.iterators.node-iterator")
 local notify = require("nvim-tree.notify")
 
+local DirectoryNode = require("nvim-tree.node.directory")
+
 local M = {}
 
 ---@param list string[]
@@ -15,7 +17,7 @@ local function to_lookup_table(list)
   return table
 end
 
----@param node Node
+---@param node DirectoryNode
 local function expand(node)
   node = node:last_group_node()
   node.open = true
@@ -36,6 +38,7 @@ end
 local function gen_iterator()
   local expansion_count = 0
 
+  ---@param parent DirectoryNode
   return function(parent)
     if parent.parent and parent.nodes and not parent.open then
       expansion_count = expansion_count + 1
@@ -44,12 +47,14 @@ local function gen_iterator()
 
     Iterator.builder(parent.nodes)
       :hidden()
+    ---@param node DirectoryNode
       :applier(function(node)
         if should_expand(expansion_count, node) then
           expansion_count = expansion_count + 1
           expand(node)
         end
       end)
+    ---@param node DirectoryNode
       :recursor(function(node)
         return expansion_count < M.MAX_FOLDER_DISCOVERY and (node.group_next and { node.group_next } or (node.open and node.nodes))
       end)
@@ -61,11 +66,16 @@ local function gen_iterator()
   end
 end
 
+---Expand the directory node or the root
 ---@param node Node
 function M.fn(node)
   local explorer = core.get_explorer()
-  node = node.nodes and node or explorer
-  if gen_iterator()(node) then
+  local parent = node:as(DirectoryNode) or explorer
+  if not parent then
+    return
+  end
+
+  if gen_iterator()(parent) then
     notify.warn("expansion iteration was halted after " .. M.MAX_FOLDER_DISCOVERY .. " discovered folders")
   end
   if explorer then

lua/nvim-tree/api.lua

@@ -10,6 +10,7 @@ local keymap = require("nvim-tree.keymap")
 local notify = require("nvim-tree.notify")
 
 local DirectoryNode = require("nvim-tree.node.directory")
+local RootNode = require("nvim-tree.node.root")
 
 local Api = {
   tree = {},
@@ -137,9 +138,9 @@ Api.tree.change_root = wrap(function(...)
 end)
 
 Api.tree.change_root_to_node = wrap_node(function(node)
-  if node.name == ".." then
+  if node.name == ".." or node:is(RootNode) then
     actions.root.change_dir.fn("..")
-  elseif node.nodes ~= nil then
+  elseif node:is(DirectoryNode) then
     actions.root.change_dir.fn(node:last_group_node().absolute_path)
   end
 end)
@@ -210,13 +211,13 @@ local function edit(mode, node)
 end
 
 ---@param mode string
----@return fun(node: table)
+---@return fun(node: Node)
 local function open_or_expand_or_dir_up(mode, toggle_group)
+  ---@param node Node
   return function(node)
     if node.name == ".." then
       actions.root.change_dir.fn("..")
     elseif node:is(DirectoryNode) then
-      ---@cast node DirectoryNode
       node:expand_or_collapse(toggle_group)
     elseif not toggle_group then
       edit(mode, node)

lua/nvim-tree/class.lua

@@ -0,0 +1,40 @@
+---Generic class, useful for inheritence.
+---@class (exact) Class
+---@field private __index? table
+local Class = {}
+
+---@param o Class?
+---@return Class
+function Class:new(o)
+  o = o or {}
+
+  setmetatable(o, self)
+  self.__index = self
+
+  return o
+end
+
+---Object is an instance of class
+---This will start with the lowest class and loop over all the superclasses.
+---@param class table
+---@return boolean
+function Class:is(class)
+  local mt = getmetatable(self)
+  while mt do
+    if mt == class then
+      return true
+    end
+    mt = getmetatable(mt)
+  end
+  return false
+end
+
+---Return object if it is an instance of class, otherwise nil
+---@generic T
+---@param class T
+---@return `T`|nil
+function Class:as(class)
+  return self:is(class) and self or nil
+end
+
+return Class

lua/nvim-tree/explorer/init.lua

@@ -5,6 +5,7 @@ local utils = require("nvim-tree.utils")
 local view = require("nvim-tree.view")
 local node_factory = require("nvim-tree.node.factory")
 
+local DirectoryNode = require("nvim-tree.node.directory")
 local RootNode = require("nvim-tree.node.root")
 local Watcher = require("nvim-tree.watcher")
 
@@ -72,12 +73,12 @@ function Explorer:create(path)
   return o
 end
 
----@param node Node
+---@param node DirectoryNode
 function Explorer:expand(node)
   self:_load(node)
 end
 
----@param node Node
+---@param node DirectoryNode
 ---@param git_status table|nil
 function Explorer:reload(node, git_status)
   local cwd = node.link_to or node.absolute_path
@@ -169,11 +170,10 @@ function Explorer:reload(node, git_status)
     end, node.nodes)
   )
 
-  local is_root = not node.parent
-  local child_folder_only = node:has_one_child_folder() and node.nodes[1]
-  if config.renderer.group_empty and not is_root and child_folder_only then
-    node.group_next = child_folder_only
-    local ns = self:reload(child_folder_only, git_status)
+  local single_child = node:single_child_directory()
+  if config.renderer.group_empty and node.parent and single_child then
+    node.group_next = single_child
+    local ns = self:reload(single_child, git_status)
     node.nodes = ns or {}
     log.profile_end(profile)
     return ns
@@ -219,7 +219,7 @@ function Explorer:refresh_parent_nodes_for_path(path)
 end
 
 ---@private
----@param node Node
+---@param node DirectoryNode
 function Explorer:_load(node)
   local cwd = node.link_to or node.absolute_path
   local git_status = git.load_project_status(cwd)
@@ -243,7 +243,7 @@ end
 ---@private
 ---@param handle uv.uv_fs_t
 ---@param cwd string
----@param node Node
+---@param node DirectoryNode
 ---@param git_status table
 ---@param parent Explorer
 function Explorer:populate_children(handle, cwd, node, git_status, parent)
@@ -295,7 +295,7 @@ function Explorer:populate_children(handle, cwd, node, git_status, parent)
 end
 
 ---@private
----@param node Node
+---@param node DirectoryNode
 ---@param status table
 ---@param parent Explorer
 ---@return Node[]|nil
@@ -311,12 +311,12 @@ function Explorer:explore(node, status, parent)
   self:populate_children(handle, cwd, node, status, parent)
 
   local is_root = not node.parent
-  local child_folder_only = node:has_one_child_folder() and node.nodes[1]
-  if config.renderer.group_empty and not is_root and child_folder_only then
-    local child_cwd = child_folder_only.link_to or child_folder_only.absolute_path
+  local single_child = node:single_child_directory()
+  if config.renderer.group_empty and not is_root and single_child then
+    local child_cwd = single_child.link_to or single_child.absolute_path
     local child_status = git.load_project_status(child_cwd)
-    node.group_next = child_folder_only
-    local ns = self:explore(child_folder_only, child_status, parent)
+    node.group_next = single_child
+    local ns = self:explore(single_child, child_status, parent)
     node.nodes = ns or {}
 
     log.profile_end(profile)
@@ -335,9 +335,10 @@ end
 function Explorer:refresh_nodes(projects)
   Iterator.builder({ self })
     :applier(function(n)
-      if n.nodes then
-        local toplevel = git.get_toplevel(n.cwd or n.link_to or n.absolute_path)
-        self:reload(n, projects[toplevel] or {})
+      local dir = n:as(DirectoryNode)
+      if dir then
+        local toplevel = git.get_toplevel(dir.cwd or dir.link_to or dir.absolute_path)
+        self:reload(dir, projects[toplevel] or {})
       end
     end)
     :recursor(function(n)

lua/nvim-tree/explorer/live-filter.lua

@@ -1,6 +1,8 @@
 local view = require("nvim-tree.view")
 local utils = require("nvim-tree.utils")
+
 local Iterator = require("nvim-tree.iterators.node-iterator")
+local DirectoryNode = require("nvim-tree.node.directory")
 
 ---@class LiveFilter
 ---@field explorer Explorer
@@ -31,17 +33,19 @@ local function reset_filter(self, node_)
     return
   end
 
-  node_.hidden_stats = vim.tbl_deep_extend("force", node_.hidden_stats or {}, {
-    live_filter = 0,
-  })
+  local dir_ = node_:as(DirectoryNode)
+  if dir_ then
+    dir_.hidden_stats = vim.tbl_deep_extend("force", dir_.hidden_stats or {}, { live_filter = 0, })
+  end
 
   Iterator.builder(node_.nodes)
     :hidden()
     :applier(function(node)
       node.hidden = false
-      node.hidden_stats = vim.tbl_deep_extend("force", node.hidden_stats or {}, {
-        live_filter = 0,
-      })
+      local dir = node:as(DirectoryNode)
+      if dir then
+        dir.hidden_stats = vim.tbl_deep_extend("force", dir.hidden_stats or {}, { live_filter = 0, })
+      end
     end)
     :iterate()
 end
@@ -85,7 +89,7 @@ local function matches(self, node)
   return vim.regex(self.filter):match_str(name) ~= nil
 end
 
----@param node_ Node?
+---@param node_ DirectoryNode?
 function LiveFilter:apply_filter(node_)
   if not self.filter or self.filter == "" then
     reset_filter(self, node_)

lua/nvim-tree/explorer/watch.lua

@@ -53,7 +53,7 @@ local function is_folder_ignored(path)
   return false
 end
 
----@param node Node
+---@param node DirectoryNode
 ---@return Watcher|nil
 function M.create_watcher(node)
   if not M.config.filesystem_watchers.enable or type(node) ~= "table" then

lua/nvim-tree/node/directory-link.lua

@@ -9,7 +9,7 @@ local DirectoryLinkNode = DirectoryNode:new()
 
 ---Static factory method
 ---@param explorer Explorer
----@param parent Node
+---@param parent DirectoryNode
 ---@param absolute_path string
 ---@param link_to string
 ---@param name string

lua/nvim-tree/node/directory.lua

@@ -1,19 +1,20 @@
 local git = require("nvim-tree.git")
 local watch = require("nvim-tree.explorer.watch")
 
-local BaseNode = require("nvim-tree.node")
+local Node = require("nvim-tree.node")
 
----@class (exact) DirectoryNode: BaseNode
+---@class (exact) DirectoryNode: Node
 ---@field has_children boolean
----@field group_next Node? -- If node is grouped, this points to the next child dir/link node
+---@field group_next DirectoryNode? -- If node is grouped, this points to the next child dir/link node
 ---@field nodes Node[]
 ---@field open boolean
+---@field watcher Watcher?
 ---@field hidden_stats table? -- Each field of this table is a key for source and value for count
-local DirectoryNode = BaseNode:new()
+local DirectoryNode = Node:new()
 
 ---Static factory method
 ---@param explorer Explorer
----@param parent Node?
+---@param parent DirectoryNode?
 ---@param absolute_path string
 ---@param name string
 ---@param fs_stat uv.fs_stat.result|nil
@@ -51,12 +52,18 @@ function DirectoryNode:create(explorer, parent, absolute_path, name, fs_stat)
 end
 
 function DirectoryNode:destroy()
-  BaseNode.destroy(self)
+  if self.watcher then
+    self.watcher:destroy()
+    self.watcher = nil
+  end
+
   if self.nodes then
     for _, node in pairs(self.nodes) do
       node:destroy()
     end
   end
+
+  Node.destroy(self)
 end
 
 ---Update the GitStatus of the directory
@@ -116,6 +123,75 @@ function DirectoryNode:get_git_status()
   end
 end
 
+---Refresh contents and git status for a single node
+function DirectoryNode:refresh()
+  local node = self:get_parent_of_group() or self
+  local toplevel = git.get_toplevel(self.absolute_path)
+
+  git.reload_project(toplevel, self.absolute_path, function()
+    local project = git.get_project(toplevel) or {}
+
+    self.explorer:reload(node, project)
+
+    node:update_parent_statuses(project, toplevel)
+
+    self.explorer.renderer:draw()
+  end)
+end
+
+-- If node is grouped, return the last node in the group. Otherwise, return the given node.
+---@return DirectoryNode
+function DirectoryNode:last_group_node()
+  return self.group_next and self.group_next:last_group_node() or self
+end
+
+---Return the one and only one child directory
+---@return DirectoryNode?
+function DirectoryNode:single_child_directory()
+  if #self.nodes == 1 then
+    return self.nodes[1]:as(DirectoryNode)
+  end
+end
+
+---@private
+-- Toggle group empty folders
+function DirectoryNode:toggle_group_folders()
+  local is_grouped = self.group_next ~= nil
+
+  if is_grouped then
+    self:ungroup_empty_folders()
+  else
+    self:group_empty_folders()
+  end
+end
+
+---Group empty folders
+-- Recursively group nodes
+---@private
+---@return Node[]
+function DirectoryNode:group_empty_folders()
+  local single_child = self:single_child_directory()
+  if self.explorer.opts.renderer.group_empty and self.parent and single_child then
+    self.group_next = single_child
+    local ns = single_child:group_empty_folders()
+    self.nodes = ns or {}
+    return ns
+  end
+  return self.nodes
+end
+
+---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
+---@private
+function DirectoryNode:ungroup_empty_folders()
+  if self.group_next then
+    self.group_next:ungroup_empty_folders()
+    self.nodes = { self.group_next }
+    self.group_next = nil
+  end
+end
+
+---@param toggle_group boolean
 function DirectoryNode:expand_or_collapse(toggle_group)
   toggle_group = toggle_group or false
   if self.has_children then
@@ -126,7 +202,7 @@ function DirectoryNode:expand_or_collapse(toggle_group)
     self.explorer:expand(self)
   end
 
-  local head_node = self:get_parent_of_group()
+  local head_node = self:get_parent_of_group() or self
   if toggle_group then
     head_node:toggle_group_folders()
   end
@@ -138,8 +214,11 @@ function DirectoryNode:expand_or_collapse(toggle_group)
   else
     next_open = not open
   end
-  for _, n in ipairs(head_node:get_all_nodes_in_group()) do
-    n.open = next_open
+
+  local node = self
+  while node do
+    node.open = next_open
+    node = node.group_next
   end
 
   self.explorer.renderer:draw()
@@ -148,7 +227,7 @@ end
 ---Create a sanitized partial copy of a node, populating children recursively.
 ---@return DirectoryNode cloned
 function DirectoryNode:clone()
-  local clone = BaseNode.clone(self) --[[@as DirectoryNode]]
+  local clone = Node.clone(self) --[[@as DirectoryNode]]
 
   clone.has_children = self.has_children
   clone.group_next = nil

lua/nvim-tree/node/factory.lua

@@ -8,7 +8,7 @@ local M = {}
 
 ---Factory function to create the appropriate Node
 ---@param explorer Explorer
----@param parent Node
+---@param parent DirectoryNode
 ---@param absolute_path string
 ---@param stat uv.fs_stat.result? -- on nil stat return nil Node
 ---@param name string

lua/nvim-tree/node/file-link.lua

@@ -9,7 +9,7 @@ local FileLinkNode = FileNode:new()
 
 ---Static factory method
 ---@param explorer Explorer
----@param parent Node
+---@param parent DirectoryNode
 ---@param absolute_path string
 ---@param link_to string
 ---@param name string

lua/nvim-tree/node/file.lua

@@ -1,15 +1,15 @@
 local git = require("nvim-tree.git")
 local utils = require("nvim-tree.utils")
 
-local BaseNode = require("nvim-tree.node")
+local Node = require("nvim-tree.node")
 
----@class (exact) FileNode: BaseNode
+---@class (exact) FileNode: Node
 ---@field extension string
-local FileNode = BaseNode:new()
+local FileNode = Node:new()
 
 ---Static factory method
 ---@param explorer Explorer
----@param parent Node
+---@param parent DirectoryNode
 ---@param absolute_path string
 ---@param name string
 ---@param fs_stat uv.fs_stat.result?
@@ -27,7 +27,6 @@ function FileNode:create(explorer, parent, absolute_path, name, fs_stat)
     is_dot = false,
     name = name,
     parent = parent,
-    watcher = nil,
     diag_status = nil,
 
     extension = string.match(name, ".?[^.]+%.(.*)") or "",
@@ -56,7 +55,7 @@ end
 ---Create a sanitized partial copy of a node
 ---@return FileNode cloned
 function FileNode:clone()
-  local clone = BaseNode.clone(self) --[[@as FileNode]]
+  local clone = Node.clone(self) --[[@as FileNode]]
 
   clone.extension = self.extension
 

lua/nvim-tree/node/init.lua

@@ -1,12 +1,14 @@
 local git = require("nvim-tree.git")
 
+local Class = require("nvim-tree.class")
+
+---TODO #2886
 ---TODO remove all @cast
 ---TODO remove all references to directory fields:
 
 ---Abstract Node class.
 ---Uses the abstract factory pattern to instantiate child instances.
----@class (exact) BaseNode
----@field private __index? table
+---@class (exact) Node: Class
 ---@field type NODE_TYPE
 ---@field explorer Explorer
 ---@field absolute_path string
@@ -15,68 +17,30 @@ local git = require("nvim-tree.git")
 ---@field git_status GitStatus?
 ---@field hidden boolean
 ---@field name string
----@field parent Node?
----@field watcher Watcher?
+---@field parent DirectoryNode?
 ---@field diag_status DiagStatus?
 ---@field is_dot boolean cached is_dotfile
-local BaseNode = {}
+local Node = Class:new()
 
----@alias Node RootNode|BaseNode|DirectoryNode|FileNode|DirectoryLinkNode|FileLinkNode
-
----@param o BaseNode?
----@return BaseNode
-function BaseNode:new(o)
-  o = o or {}
-
-  setmetatable(o, self)
-  self.__index = self
-
-  return o
-end
-
-function BaseNode:destroy()
-  if self.watcher then
-    self.watcher:destroy()
-    self.watcher = nil
-  end
-end
-
----From plenary
----Checks if the object is an instance
----This will start with the lowest class and loop over all the superclasses.
----@param self BaseNode
----@param T BaseNode
----@return boolean
-function BaseNode:is(T)
-  local mt = getmetatable(self)
-  while mt do
-    if mt == T then
-      return true
-    end
-    mt = getmetatable(mt)
-  end
-  return false
-end
-
----@return boolean
-function BaseNode:has_one_child_folder()
-  return #self.nodes == 1 and self.nodes[1].nodes and vim.loop.fs_access(self.nodes[1].absolute_path, "R") or false
+function Node:destroy()
 end
 
 --luacheck: push ignore 212
 ---Update the GitStatus of the node
 ---@param parent_ignored boolean
 ---@param status table?
-function BaseNode:update_git_status(parent_ignored, status) ---@diagnostic disable-line: unused-local
+function Node:update_git_status(parent_ignored, status) ---@diagnostic disable-line: unused-local
+  ---TODO find a way to declare abstract methods
 end
+
 --luacheck: pop
 
 ---@return GitStatus?
-function BaseNode:get_git_status()
+function Node:get_git_status()
 end
 
 ---@param projects table
-function BaseNode:reload_node_status(projects)
+function Node:reload_node_status(projects)
   local toplevel = git.get_toplevel(self.absolute_path)
   local status = projects[toplevel] or {}
   for _, node in ipairs(self.nodes) do
@@ -88,13 +52,13 @@ function BaseNode:reload_node_status(projects)
 end
 
 ---@return boolean
-function BaseNode:is_git_ignored()
+function Node:is_git_ignored()
   return self.git_status ~= nil and self.git_status.file == "!!"
 end
 
 ---Node or one of its parents begins with a dot
 ---@return boolean
-function BaseNode:is_dotfile()
+function Node:is_dotfile()
   if
     self.is_dot
     or (self.name and (self.name:sub(1, 1) == "."))
@@ -106,22 +70,9 @@ function BaseNode:is_dotfile()
   return false
 end
 
--- If node is grouped, return the last node in the group. Otherwise, return the given node.
----@return Node
-function BaseNode:last_group_node()
-  local node = self
-  --- @cast node BaseNode
-
-  while node.group_next do
-    node = node.group_next
-  end
-
-  return node
-end
-
 ---@param project table?
 ---@param root string?
-function BaseNode:update_parent_statuses(project, root)
+function Node:update_parent_statuses(project, root)
   local node = self
   while project and node do
     -- step up to the containing project
@@ -151,88 +102,30 @@ function BaseNode:update_parent_statuses(project, root)
   end
 end
 
----Refresh contents and git status for a single node
-function BaseNode:refresh()
-  local parent_node = self:get_parent_of_group()
-  local toplevel = git.get_toplevel(self.absolute_path)
-
-  git.reload_project(toplevel, self.absolute_path, function()
-    local project = git.get_project(toplevel) or {}
-
-    self.explorer:reload(parent_node, project)
-
-    parent_node:update_parent_statuses(project, toplevel)
-
-    self.explorer.renderer:draw()
-  end)
-end
-
----Get the highest parent of grouped nodes
----@return Node node or parent
-function BaseNode:get_parent_of_group()
-  local node = self
-  while node and node.parent and node.parent.group_next do
-    node = node.parent or node
+---Get the highest parent of grouped nodes, nil when not grouped
+---@return DirectoryNode?
+function Node:get_parent_of_group()
+  if not self.parent or not self.parent.group_next then
+    return nil
   end
-  return node
-end
 
----@return Node[]
-function BaseNode:get_all_nodes_in_group()
-  local next_node = self:get_parent_of_group()
-  local nodes = {}
-  while next_node do
-    table.insert(nodes, next_node)
-    next_node = next_node.group_next
-  end
-  return nodes
-end
-
--- Toggle group empty folders
-function BaseNode:toggle_group_folders()
-  local is_grouped = self.group_next ~= nil
-
-  if is_grouped then
-    self:ungroup_empty_folders()
-  else
-    self:group_empty_folders()
-  end
-end
-
----Group empty folders
--- Recursively group nodes
----@return Node[]
-function BaseNode:group_empty_folders()
-  local is_root = not self.parent
-  local child_folder_only = self:has_one_child_folder() and self.nodes[1]
-  if self.explorer.opts.renderer.group_empty and not is_root and child_folder_only then
-    ---@cast self DirectoryNode -- TODO #2886 move this to the class
-    self.group_next = child_folder_only
-    local ns = child_folder_only:group_empty_folders()
-    self.nodes = ns or {}
-    return ns
-  end
-  return self.nodes
-end
-
----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
-function BaseNode:ungroup_empty_folders()
-  local cur = self
-  while cur and cur.group_next do
-    cur.nodes = { cur.group_next }
-    cur.group_next = nil
-    cur = cur.nodes[1]
+  local node = self.parent
+  while node do
+    if node.parent and node.parent.group_next then
+      node = node.parent
+    else
+      return node
+    end
   end
 end
 
 ---Create a sanitized partial copy of a node, populating children recursively.
----@return BaseNode cloned
-function BaseNode:clone()
+---@return Node cloned
+function Node:clone()
   ---@type Explorer
   local explorer_placeholder = nil
 
-  ---@type BaseNode
+  ---@type Node
   local clone = {
     type = self.type,
     explorer = explorer_placeholder,
@@ -244,11 +137,10 @@ function BaseNode:clone()
     is_dot = self.is_dot,
     name = self.name,
     parent = nil,
-    watcher = nil,
     diag_status = nil,
   }
 
   return clone
 end
 
-return BaseNode
+return Node

lua/nvim-tree/renderer/builder.lua

@@ -2,6 +2,10 @@ local notify = require("nvim-tree.notify")
 local utils = require("nvim-tree.utils")
 local view = require("nvim-tree.view")
 
+local DirectoryLinkNode = require("nvim-tree.node.directory-link")
+local DirectoryNode = require("nvim-tree.node.directory")
+local FileLinkNode = require("nvim-tree.node.file-link")
+
 local DecoratorBookmarks = require("nvim-tree.renderer.decorator.bookmarks")
 local DecoratorCopied = require("nvim-tree.renderer.decorator.copied")
 local DecoratorCut = require("nvim-tree.renderer.decorator.cut")
@@ -341,19 +345,21 @@ function Builder:add_highlights(node)
   return icon_hl_group, name_hl_group
 end
 
+---Insert node line into self.lines, calling Builder:build_lines for each directory
 ---@private
+---@param node Node
+---@param idx integer line number starting at 1
+---@param num_children integer of node
 function Builder:build_line(node, idx, num_children)
   -- various components
   local indent_markers = pad.get_indent_markers(self.depth, idx, num_children, node, self.markers)
   local arrows = pad.get_arrows(node)
 
   -- main components
-  local is_folder = node.nodes ~= nil
-  local is_symlink = node.link_to ~= nil
   local icon, name
-  if is_folder then
+  if node:is(DirectoryNode) then
     icon, name = self:build_folder(node)
-  elseif is_symlink then
+  elseif node:is(DirectoryLinkNode) or node:is(FileLinkNode) then
     icon, name = self:build_symlink(node)
   else
     icon, name = self:build_file(node)
@@ -369,11 +375,13 @@ function Builder:build_line(node, idx, num_children)
 
   self.index = self.index + 1
 
-  node = node:last_group_node()
-  if node.open then
-    self.depth = self.depth + 1
-    self:build_lines(node)
-    self.depth = self.depth - 1
+  if node:is(DirectoryNode) then
+    node = node:last_group_node()
+    if node.open then
+      self.depth = self.depth + 1
+      self:build_lines(node)
+      self.depth = self.depth - 1
+    end
   end
 end
 
@@ -403,8 +411,11 @@ function Builder:add_hidden_count_string(node, idx, num_children)
   end
 end
 
+---Number of visible nodes
 ---@private
-function Builder:get_nodes_number(nodes)
+---@param nodes Node[]
+---@return integer
+function Builder:num_visible(nodes)
   if not self.explorer.live_filter.filter then
     return #nodes
   end
@@ -423,7 +434,7 @@ function Builder:build_lines(node)
   if not node then
     node = self.explorer
   end
-  local num_children = self:get_nodes_number(node.nodes)
+  local num_children = self:num_visible(node.nodes)
   local idx = 1
   for _, n in ipairs(node.nodes) do
     if not n.hidden then

lua/nvim-tree/renderer/decorator/init.lua

@@ -1,26 +1,16 @@
+local Class = require("nvim-tree.class")
+
 local HL_POSITION = require("nvim-tree.enum").HL_POSITION
 local ICON_PLACEMENT = require("nvim-tree.enum").ICON_PLACEMENT
 
 ---Abstract Decorator
 ---Uses the factory pattern to instantiate child instances.
----@class (exact) Decorator
----@field private __index? table
+---@class (exact) Decorator: Class
 ---@field protected explorer Explorer
 ---@field protected enabled boolean
 ---@field protected hl_pos HL_POSITION
 ---@field protected icon_placement ICON_PLACEMENT
-local Decorator = {}
-
----@param o Decorator|nil
----@return Decorator
-function Decorator:new(o)
-  o = o or {}
-
-  setmetatable(o, self)
-  self.__index = self
-
-  return o
-end
+local Decorator = Class:new()
 
 ---Maybe highlight groups
 ---@param node Node