Reject stale timer callbacks

2 files changed, 26 insertions, 2 deletions

diff --git a/lua/clever_f/feedback_service.lua b/lua/clever_f/feedback_service.lua
index d84fcb3..edaa39d 100644
--- a/lua/clever_f/feedback_service.lua
+++ b/lua/clever_f/feedback_service.lua
@@ -712,8 +712,11 @@ function FeedbackService:cancel_highlight_timer()
   return identity
 end
 
-function FeedbackService:handle_highlight_timer()
-  return false
+function FeedbackService:handle_highlight_timer(callback_identity)
+  if callback_identity == nil then
+    fail("highlight timer callback identity must be present", 2)
+  end
+  return callback_identity == service_records[self].state.highlight_timer
 end
 
 function FeedbackService:start_highlight_timer()
diff --git a/tests/run.lua b/tests/run.lua
index a511fb0..c3e7009 100644
--- a/tests/run.lua
+++ b/tests/run.lua
@@ -6645,6 +6645,27 @@ test("Each new highlight timer identity is stored in sequence state", function()
   same(40, host:timers()[second].delay_ms)
 end)
 
+test("Timer callbacks compare their identity with current state", function()
+  local state, transitions = fresh_sequence_state()
+  local host = MemoryHost.new({
+    configuration = {
+      mark_char = true,
+      highlight_timeout_ms = 10,
+    },
+  })
+  local feedback = feedback_service.new({
+    host = host,
+    transitions = transitions,
+  })
+  local stale = feedback:start_highlight_timer()
+  local current = feedback:start_highlight_timer()
+
+  falsy(feedback:handle_highlight_timer(stale))
+  same(current, state.highlight_timer)
+  truthy(feedback:handle_highlight_timer(current))
+  same(current, state.highlight_timer)
+end)
+
 for _, item in ipairs(tests) do
   local ok, failure = xpcall(item.body, debug.traceback)
   if not ok then