perf(lsp): reduce polling handles for workspace/didChangeWatchedFiles (#23500)

Co-authored-by: Lewis Russell <lewis6991@gmail.com>

runtime/lua/vim/_watch.lua

@@ -11,6 +11,7 @@ M.FileChangeType = vim.tbl_add_reverse_lookup({
 --- Joins filepath elements by static '/' separator
 ---
 ---@param ... (string) The path elements.
+---@return string
 local function filepath_join(...)
   return table.concat({ ... }, '/')
 end
@@ -36,7 +37,7 @@ end
 ---     - uvflags (table|nil)
 ---                Same flags as accepted by |uv.fs_event_start()|
 ---@param callback (function) The function called when new events
----@returns (function) A function to stop the watch
+---@return (function) A function to stop the watch
 function M.watch(path, opts, callback)
   vim.validate({
     path = { path, 'string', false },
@@ -75,10 +76,25 @@ end
 
 local default_poll_interval_ms = 2000
 
+--- @class watch.Watches
+--- @field is_dir boolean
+--- @field children? table<string,watch.Watches>
+--- @field cancel? fun()
+--- @field started? boolean
+--- @field handle? uv_fs_poll_t
+
+--- @class watch.PollOpts
+--- @field interval? integer
+--- @field include_pattern? userdata
+--- @field exclude_pattern? userdata
+
 ---@private
 --- Implementation for poll, hiding internally-used parameters.
 ---
----@param watches (table|nil) A tree structure to maintain state for recursive watches.
+---@param path string
+---@param opts watch.PollOpts
+---@param callback fun(patch: string, filechangetype: integer)
+---@param watches (watch.Watches|nil) A tree structure to maintain state for recursive watches.
 ---     - handle (uv_fs_poll_t)
 ---               The libuv handle
 ---     - cancel (function)
@@ -88,15 +104,36 @@ local default_poll_interval_ms = 2000
 ---               be invoked recursively)
 ---     - children (table|nil)
 ---               A mapping of directory entry name to its recursive watches
---      - started (boolean|nil)
---                Whether or not the watcher has first been initialized. Used
---                to prevent a flood of Created events on startup.
+---     - started (boolean|nil)
+---               Whether or not the watcher has first been initialized. Used
+---               to prevent a flood of Created events on startup.
+---@return fun() Cancel function
 local function poll_internal(path, opts, callback, watches)
   path = vim.fs.normalize(path)
   local interval = opts and opts.interval or default_poll_interval_ms
   watches = watches or {
     is_dir = true,
   }
+  watches.cancel = function()
+    if watches.children then
+      for _, w in pairs(watches.children) do
+        w.cancel()
+      end
+    end
+    if watches.handle then
+      stop(watches.handle)
+    end
+  end
+
+  local function incl_match()
+    return not opts.include_pattern or opts.include_pattern:match(path) ~= nil
+  end
+  local function excl_match()
+    return opts.exclude_pattern and opts.exclude_pattern:match(path) ~= nil
+  end
+  if not watches.is_dir and not incl_match() or excl_match() then
+    return watches.cancel
+  end
 
   if not watches.handle then
     local poll, new_err = vim.uv.new_fs_poll()
@@ -120,18 +157,9 @@ local function poll_internal(path, opts, callback, watches)
     end
   end
 
-  watches.cancel = function()
-    if watches.children then
-      for _, w in pairs(watches.children) do
-        w.cancel()
-      end
-    end
-    stop(watches.handle)
-  end
-
   if watches.is_dir then
     watches.children = watches.children or {}
-    local exists = {}
+    local exists = {} --- @type table<string,true>
     for name, ftype in vim.fs.dir(path) do
       exists[name] = true
       if not watches.children[name] then
@@ -143,14 +171,16 @@ local function poll_internal(path, opts, callback, watches)
       end
     end
 
-    local newchildren = {}
+    local newchildren = {} ---@type table<string,watch.Watches>
     for name, watch in pairs(watches.children) do
       if exists[name] then
         newchildren[name] = watch
       else
         watch.cancel()
         watches.children[name] = nil
-        callback(path .. '/' .. name, M.FileChangeType.Deleted)
+        if watch.handle then
+          callback(path .. '/' .. name, M.FileChangeType.Deleted)
+        end
       end
     end
     watches.children = newchildren
@@ -168,6 +198,15 @@ end
 ---@param opts (table|nil) Additional options
 ---     - interval (number|nil)
 ---                Polling interval in ms as passed to |uv.fs_poll_start()|. Defaults to 2000.
+---     - include_pattern (LPeg pattern|nil)
+---                An |lpeg| pattern. Only changes to files whose full paths match the pattern
+---                will be reported. Only matches against non-directoriess, all directories will
+---                be watched for new potentially-matching files. exclude_pattern can be used to
+---                filter out directories. When nil, matches any file name.
+---     - exclude_pattern (LPeg pattern|nil)
+---                An |lpeg| pattern. Only changes to files and directories whose full path does
+---                not match the pattern will be reported. Matches against both files and
+---                directories. When nil, matches nothing.
 ---@param callback (function) The function called when new events
 ---@returns (function) A function to stop the watch.
 function M.poll(path, opts, callback)