fix(filesystem): make async_scan asynchronous

Replace `uv.fs_scandir` and `uv.fs_scandir_next` with their async alternatives, `uv.fs_opendir` and `uv.fs_readdir`

Fix: #609

Author: musjj

lua/neo-tree/sources/filesystem/lib/fs_scan.lua

@@ -127,45 +127,59 @@ local function async_scan(context, path)
 
   -- from https://github.com/nvim-lua/plenary.nvim/blob/master/lua/plenary/scandir.lua
   local function read_dir(current_dir, ctx)
-    local on_fs_scandir = function(err, fd)
+    local function on_fs_opendir(err, dir)
       if err then
         log.error(current_dir, ": ", err)
       else
-        while true do
-          local name, typ = uv.fs_scandir_next(fd)
-          if name == nil then
-            break
-          end
-          local entry = utils.path_join(current_dir, name)
-          local success, item = pcall(file_items.create_item, ctx, entry, typ)
-          if success then
-            if ctx.recursive and item.type == "directory" then
-              ctx.directories_to_scan = ctx.directories_to_scan + 1
-              table.insert(ctx.paths_to_load, item.path)
-            end
+        local function on_fs_readdir(err, entries)
+          if err then
+            log.error(current_dir, ": ", err)
           else
-            log.error("error creating item for ", path)
+            if entries then
+              for _, entry in ipairs(entries) do
+                local success, item = pcall(
+                  file_items.create_item,
+                  ctx,
+                  utils.path_join(current_dir, entry.name),
+                  entry.type
+                )
+                if success then
+                  if ctx.recursive and item.type == "directory" then
+                    ctx.directories_to_scan = ctx.directories_to_scan + 1
+                    table.insert(ctx.paths_to_load, item.path)
+                  end
+                else
+                  log.error("error creating item for ", path)
+                end
+              end
+
+              uv.fs_readdir(dir, on_fs_readdir)
+            else
+              uv.fs_closedir(dir)
+              on_directory_loaded(ctx, current_dir)
+              ctx.directories_scanned = ctx.directories_scanned + 1
+              if ctx.directories_scanned == #ctx.paths_to_load then
+                ctx.on_exit()
+              end
+            end
           end
-        end
-        on_directory_loaded(ctx, current_dir)
-        ctx.directories_scanned = ctx.directories_scanned + 1
-        if ctx.directories_scanned == #ctx.paths_to_load then
-          ctx.on_exit()
+
+          --local next_path = dir_complete(ctx, current_dir)
+          --if next_path then
+          --  local success, error = pcall(read_dir, next_path)
+          --  if not success then
+          --    log.error(next_path, ": ", error)
+          --  end
+          --else
+          --  on_exit()
+          --end
         end
 
-        --local next_path = dir_complete(ctx, current_dir)
-        --if next_path then
-        --  local success, error = pcall(read_dir, next_path)
-        --  if not success then
-        --    log.error(next_path, ": ", error)
-        --  end
-        --else
-        --  on_exit()
-        --end
+        uv.fs_readdir(dir, on_fs_readdir)
       end
     end
 
-    uv.fs_scandir(current_dir, on_fs_scandir)
+    uv.fs_opendir(current_dir, on_fs_opendir)
   end
 
   --local first = table.remove(context.paths_to_load)