fix (sidebar) rendering and applying snippets for new files

lua/avante/sidebar.lua

@@ -232,6 +232,14 @@ local function transform_result_content(selected_files, result_content, prev_fil
         ::continue1::
       end
 
+      -- when the filetype isn't detected, fallback to matching based on filepath.
+      -- can happen if the llm tries to edit or create a file outside of it's context.
+      if not match_filetype then
+        local snippet_file_path = current_filepath or prev_filepath
+        local snippet_file_type = vim.filetype.match({ filename = snippet_file_path }) or "unknown"
+        match_filetype = snippet_file_type
+      end
+
       local search_start_tag_idx_in_transformed_lines = 0
       for j = 1, #transformed_lines do
         if transformed_lines[j] == "<SEARCH>" then
@@ -430,7 +438,8 @@ local function ensure_snippets_no_overlap(snippets_map)
     table.sort(snippets, function(a, b) return a.range[1] < b.range[1] end)
 
     local original_content = ""
-    if Utils.file.exists(filepath) then original_content = Utils.file.read_content(filepath) or "" end
+    local file_exists = Utils.file.exists(filepath)
+    if file_exists then original_content = Utils.file.read_content(filepath) or "" end
 
     local original_lines = vim.split(original_content, "\n")
 
@@ -440,6 +449,10 @@ local function ensure_snippets_no_overlap(snippets_map)
       if snippet.range[1] > last_end_line then
         table.insert(new_snippets, snippet)
         last_end_line = snippet.range[2]
+      elseif not file_exists and #snippets <= 1 then
+        -- if the file doesn't exist, and we only have 1 snippet, then we don't have to check for overlaps.
+        table.insert(new_snippets, snippet)
+        last_end_line = snippet.range[2]
       else
         local snippet_lines = vim.split(snippet.content, "\n")
         -- Trim the overlapping part