fix(log): batch error notifications into one per burst

lua/flutter-tools/commands.lua

@@ -87,10 +87,31 @@ local function has_recoverable_error(lines)
   return false, nil
 end
 
+local ERROR_NOTIFY_DELAY_MS = 200
+---@type string[]
+local pending_errors = {}
+local error_timer = nil
+
+local function flush_errors()
+  if #pending_errors == 0 then return end
+  local lines = pending_errors
+  pending_errors = {}
+  ui.notify(lines, ui.ERROR, { timeout = 5000 })
+end
+
+---stderr arrives one line at a time, so collect a burst of lines into a single notification
+---@param line string
+local function queue_error_notification(line)
+  table.insert(pending_errors, line)
+  if not error_timer then error_timer = assert(vim.uv.new_timer()) end
+  error_timer:stop()
+  error_timer:start(ERROR_NOTIFY_DELAY_MS, 0, vim.schedule_wrap(flush_errors))
+end
+
 ---Handle output from flutter run command
 ---@param is_err boolean if this is stdout or stderr
 local function on_run_data(is_err, data)
-  if is_err and config.dev_log.notify_errors then ui.notify(data, ui.ERROR, { timeout = 5000 }) end
+  if is_err and config.dev_log.notify_errors then queue_error_notification(data) end
   update_device_from_output(data)
   dev_log.log(data)
 end
@@ -660,6 +681,7 @@ if __TEST then
   M.__get_run_args = get_run_args
   M.__update_device_from_output = update_device_from_output
   M.__set_current_device = set_current_device
+  M.__on_run_data = on_run_data
 end
 
 return M

lua/flutter-tools/runners/debugger_runner.lua

@@ -239,7 +239,7 @@ function DebuggerRunner:run(
       if body and body.output then
         for line in body.output:gmatch("[^\r\n]+") do
           if not started then table.insert(before_start_logs, line) end
-          on_run_data(body.category == "sterr", line)
+          on_run_data(body.category == "stderr", line)
         end
       end
     end,
@@ -305,7 +305,7 @@ function DebuggerRunner:attach(paths, args, cwd, on_run_data, on_run_exit)
     if body and body.output then
       for line in body.output:gmatch("[^\r\n]+") do
         if not started then table.insert(before_start_logs, line) end
-        on_run_data(body.category == "sterr", line)
+        on_run_data(body.category == "stderr", line)
       end
     end
   end, function(before_start_logs) on_run_exit(before_start_logs, args) end)

tests/commands_spec.lua

@@ -109,4 +109,23 @@ describe("commands", function()
 
     assert.is_nil(commands.current_device())
   end)
+
+  it("should batch consecutive error lines into one notification", function()
+    local config = require("flutter-tools.config")
+    local ui = require("flutter-tools.ui")
+    local original_notify = ui.notify
+    local notifications = {}
+    ui.notify = function(msg) table.insert(notifications, msg) end
+    config.dev_log.notify_errors = true
+
+    commands.__on_run_data(true, "Error: first line")
+    commands.__on_run_data(true, "second line")
+    commands.__on_run_data(false, "regular output")
+    commands.__on_run_data(true, "third line")
+    vim.wait(1000, function() return #notifications > 0 end)
+
+    config.dev_log.notify_errors = false
+    ui.notify = original_notify
+    assert.are.same({ { "Error: first line", "second line", "third line" } }, notifications)
+  end)
 end)