fix(filesystem): ensure replacemnt for deleted buffer is a real file (#1176)

fixes #1174

Author: cseickel

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

@@ -16,12 +16,36 @@ local Path = require("plenary").path
 
 local M = {}
 
+local function find_replacement_buffer(for_buf)
+  local bufs = vim.api.nvim_list_bufs()
+
+  -- make sure the alternate buffer is at the top of the list
+  local alt = vim.fn.bufnr("#")
+  if alt ~= -1 and alt ~= for_buf then
+    table.insert(bufs, 1, alt)
+  end
+
+  -- find the first valid real file buffer
+  for _, buf in ipairs(bufs) do
+    if buf ~= for_buf then
+      local is_valid = vim.api.nvim_buf_is_valid(buf)
+      if is_valid then
+        local buftype = vim.api.nvim_buf_get_option(buf, "buftype")
+        if buftype == "" then
+          return buf
+        end
+      end
+    end
+  end
+  return -1
+end
+
 local function clear_buffer(path)
   local buf = utils.find_buffer_by_name(path)
   if buf < 1 then
     return
   end
-  local alt = vim.fn.bufnr("#")
+  local alt = find_replacement_buffer(buf)
   -- Check all windows to see if they are using the buffer
   for _, win in ipairs(vim.api.nvim_list_wins()) do
     if vim.api.nvim_win_is_valid(win) and vim.api.nvim_win_get_buf(win) == buf then