fix: thrown error when trying to use codebase with no buffer opened (#1541)

* Fix - Fix thrown error when trying to use @codebase with no buffer opened

* Style - Fix stylua formatting in repo_map and sidebar

* Fix - Restore code selection handling in sidebar
This was a mistake on my part while rushing to make the PR. I deleted an
unrelated commit that got sent by mistake, and during the second review,
I didn't notice that this important code selection functionality was
removed. The code has now been properly restored.

lua/avante/repo_map.lua

@@ -62,6 +62,12 @@ end
 local cache = {}
 
 function RepoMap.get_repo_map(file_ext)
+  -- Add safety check for file_ext
+  if not file_ext then
+    Utils.warn("No file extension available - please open a file first")
+    return {}
+  end
+
   local repo_map = RepoMap._get_repo_map(file_ext) or {}
   if not repo_map or next(repo_map) == nil then
     Utils.warn("The repo map is empty. Maybe do not support this language: " .. file_ext)
@@ -70,7 +76,15 @@ function RepoMap.get_repo_map(file_ext)
 end
 
 function RepoMap._get_repo_map(file_ext)
-  file_ext = file_ext or vim.fn.expand("%:e")
+  -- Add safety check at the start of the function
+  if not file_ext then
+    local current_buf = vim.api.nvim_get_current_buf()
+    local buf_name = vim.api.nvim_buf_get_name(current_buf)
+    if buf_name and buf_name ~= "" then file_ext = vim.fn.fnamemodify(buf_name, ":e") end
+
+    if not file_ext or file_ext == "" then return {} end
+  end
+
   local project_root = Utils.root.get()
   local cache_key = project_root .. "." .. file_ext
   local cached = cache[cache_key]

lua/avante/sidebar.lua

@@ -2356,6 +2356,11 @@ function Sidebar:create_input_container(opts)
   ---@param cb fun(opts: AvanteGeneratePromptsOptions): nil
   local function get_generate_prompts_options(request, summarize_memory, cb)
     local filetype = api.nvim_get_option_value("filetype", { buf = self.code.bufnr })
+    local file_ext = nil
+
+    -- Get file extension safely
+    local buf_name = api.nvim_buf_get_name(self.code.bufnr)
+    if buf_name and buf_name ~= "" then file_ext = vim.fn.fnamemodify(buf_name, ":e") end
 
     ---@type AvanteSelectedCode | nil
     local selected_code = nil
@@ -2370,11 +2375,9 @@ function Sidebar:create_input_container(opts)
     local mentions = Utils.extract_mentions(request)
     request = mentions.new_content
 
-    local file_ext = api.nvim_buf_get_name(self.code.bufnr):match("^.+%.(.+)$")
+    local project_context = mentions.enable_project_context and file_ext and RepoMap.get_repo_map(file_ext) or nil
 
-    local project_context = mentions.enable_project_context and RepoMap.get_repo_map(file_ext) or nil
+    local selected_files_contents = self.file_selector:get_selected_files_contents() or {}
-
-    local selected_files_contents = self.file_selector:get_selected_files_contents()
 
     local diagnostics = nil
     if mentions.enable_diagnostics then
@@ -2428,6 +2431,11 @@ function Sidebar:create_input_container(opts)
 
   ---@param request string
   local function handle_submit(request)
+    if request:match("@codebase") and not vim.fn.expand("%:e") then
+      self:update_content("Please open a file first before using @codebase", { focus = false, scroll = false })
+      return
+    end
+
     local model = Config.has_provider(Config.provider) and Config.get_provider_config(Config.provider).model
       or "default"