From 2ecfe587a087e7df3ca91f797844acdf3509b0ea Mon Sep 17 00:00:00 2001
From: Peter Cardenas <16930781+PeterCardenas@users.noreply.github.com>
Date: Tue, 1 Jul 2025 09:59:01 -0700
Subject: [PATCH] feat: parse and conditionally add cursor rules to system
 prompt (#2385)

---
 lua/avante/llm.lua           |  2 ++
 lua/avante/utils/prompts.lua | 48 ++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/lua/avante/llm.lua b/lua/avante/llm.lua
index 4173eaa..2a33a58 100644
--- a/lua/avante/llm.lua
+++ b/lua/avante/llm.lua
@@ -388,6 +388,8 @@ function M.generate_prompts(opts)
 
   local agents_rules = Prompts.get_agents_rules_prompt()
   if agents_rules then system_prompt = system_prompt .. "\n\n" .. agents_rules end
+  local cursor_rules = Prompts.get_cursor_rules_prompt(selected_files)
+  if cursor_rules then system_prompt = system_prompt .. "\n\n" .. cursor_rules end
 
   ---@type AvantePromptOptions
   return {
diff --git a/lua/avante/utils/prompts.lua b/lua/avante/utils/prompts.lua
index 54c21be..75ab487 100644
--- a/lua/avante/utils/prompts.lua
+++ b/lua/avante/utils/prompts.lua
@@ -233,4 +233,52 @@ function M.get_agents_rules_prompt()
   return nil
 end
 
+---@param selected_files AvanteSelectedFile[]
+---@return string | nil
+function M.get_cursor_rules_prompt(selected_files)
+  local Utils = require("avante.utils")
+  local project_root = Utils.get_project_root()
+  local accumulated_content = ""
+
+  ---@type string[]
+  local mdc_files = vim.fn.globpath(Utils.join_paths(project_root, ".cursor/rules"), "*.mdc", false, true)
+  for _, file_path in ipairs(mdc_files) do
+    ---@type string[]
+    local content = vim.fn.readfile(file_path)
+    if content[1] ~= "---" or content[5] ~= "---" then goto continue end
+    local header, body = table.concat(content, "\n", 2, 4), table.concat(content, "\n", 6)
+    local _description, globs, alwaysApply = header:match("description:%s*(.*)\nglobs:%s*(.*)\nalwaysApply:%s*(.*)")
+
+    if not globs then goto continue end
+    globs = vim.trim(globs)
+    -- TODO: When empty string, this means the agent should request for this rule ad-hoc.
+    if globs == "" then goto continue end
+    local globs_array = vim.split(globs, ",%s*")
+    local path_regexes = {} ---@type string[]
+    for _, glob in ipairs(globs_array) do
+      path_regexes[#path_regexes + 1] = glob:gsub("%*%*", ".+"):gsub("%*", "[^/]*")
+      path_regexes[#path_regexes + 1] = glob:gsub("%*%*/", ""):gsub("%*", "[^/]*")
+    end
+    local always_apply = alwaysApply == "true"
+
+    if always_apply then
+      accumulated_content = accumulated_content .. "\n" .. body
+    else
+      local matched = false
+      for _, selected_file in ipairs(selected_files) do
+        for _, path_regex in ipairs(path_regexes) do
+          if string.match(selected_file.path, path_regex) then
+            accumulated_content = accumulated_content .. "\n" .. body
+            matched = true
+            break
+          end
+        end
+        if matched then break end
+      end
+    end
+    ::continue::
+  end
+  return accumulated_content ~= "" and accumulated_content or nil
+end
+
 return M