feat(#2515): add option to change grouped folders name with custom function

doc/nvim-tree-lua.txt

@@ -795,7 +795,9 @@ Appends a trailing slash to folder names.
 
 *nvim-tree.renderer.group_empty*
 Compact folders that only contain a single folder into one node.
-  Type: `boolean`, Default: `false`
+Boolean or function that takes one argument (the relative path
+of grouped folders) and returns a string to be displayed.
+  Type: `boolean | function(relative_path):string`, Default: `false`
 
 *nvim-tree.renderer.full_name*
 Display node whose name length is wider than the width of nvim-tree window in

lua/nvim-tree.lua

@@ -640,6 +640,7 @@ local ACCEPTED_TYPES = {
     },
   },
   renderer = {
+    group_empty = { "boolean", "function" },
     root_folder_label = { "function", "string", "boolean" },
   },
   actions = {

lua/nvim-tree/renderer/builder.lua

@@ -1,5 +1,6 @@
 local utils = require "nvim-tree.utils"
 local core = require "nvim-tree.core"
+local notify = require "nvim-tree.notify"
 
 local git = require "nvim-tree.renderer.components.git"
 local pad = require "nvim-tree.renderer.components.padding"
@@ -105,6 +106,13 @@ function Builder:configure_symlink_destination(show)
   return self
 end
 
+function Builder:configure_group_name_modifier(group_name_modifier)
+  if type(group_name_modifier) == "function" then
+    self.group_name_modifier = group_name_modifier
+  end
+  return self
+end
+
 function Builder:_insert_highlight(group, start, end_)
   table.insert(self.highlights, { group, self.index, start, end_ or -1 })
 end
@@ -113,14 +121,24 @@ function Builder:_insert_line(line)
   table.insert(self.lines, line)
 end
 
-local function get_folder_name(node)
+function Builder:_get_folder_name(node)
   local name = node.name
   local next = node.group_next
   while next do
     name = name .. "/" .. next.name
     next = next.group_next
   end
-  return name
+
+  if node.group_next and self.group_name_modifier then
+    local new_name = self.group_name_modifier(name)
+    if type(new_name) == "string" then
+      name = new_name
+    else
+      notify.warn(string.format("Invalid return type for field renderer.group_empty. Expected string, got %s", type(new_name)))
+    end
+  end
+
+  return name .. self.trailing_slash
 end
 
 ---@class HighlightedString
@@ -152,7 +170,7 @@ end
 function Builder:_build_folder(node)
   local has_children = #node.nodes ~= 0 or node.has_children
   local icon, icon_hl = icons.get_folder_icon(node, has_children)
-  local foldername = get_folder_name(node) .. self.trailing_slash
+  local foldername = self:_get_folder_name(node)
 
   if #icon > 0 and icon_hl == nil then
     if node.open then

lua/nvim-tree/renderer/init.lua

@@ -80,6 +80,7 @@ function M.draw(unloaded_bufnr)
     :configure_modified_placement(M.config.icons.modified_placement)
     :configure_symlink_destination(M.config.symlink_destination)
     :configure_filter(live_filter.filter, live_filter.prefix)
+    :configure_group_name_modifier(M.config.group_empty)
     :build_header(view.is_root_folder_visible(core.get_cwd()))
     :build(core.get_explorer(), unloaded_bufnr)
     :unwrap()