mp.input: avoid rare race condition when supplying completions

It was previously possible for completion messages to be received by a
new input request, if one was created while the message was in transit.

Since it is trivial to avoid this by passing the script name and
existing handle_id value, we may as well do so and guarantee that there
will not be any data races.

Author: CogentRedTester

player/javascript/defaults.js

@@ -665,8 +665,13 @@ function register_event_handler(t) {
             var result = t[type].apply(null, args);
 
             if (type == "complete" && result) {
-                mp.commandv("script-message-to", "console", "complete",
-                            JSON.stringify(result[0]), result[1], result[2] || "");
+                mp.commandv("script-message-to", "console", "complete", JSON.stringify({
+                                script_name: mp.script_name,
+                                handler_id: handler_id,
+                                list: result[0],
+                                start_pos: result[1],
+                                append: result[2] || "",
+                            }));
             }
         }
 

player/lua/console.lua

@@ -1795,17 +1795,21 @@ mp.register_script_message("set-log", function (log)
     render()
 end)
 
-mp.register_script_message("complete", function (list, start_pos, append)
-    if line ~= completion_old_line or cursor ~= completion_old_cursor then
+mp.register_script_message("complete", function (message)
+    message = utils.parse_json(message)
+
+    if message.script_name ~= input_caller or message.handler_id ~= input_caller_handler then
+        return
+    elseif line ~= completion_old_line or cursor ~= completion_old_cursor then
         return
     end
 
     completion_buffer = {}
     selected_completion_index = 0
-    local completions = utils.parse_json(list)
+    local completions = message.list
     table.sort(completions)
-    completion_pos = start_pos
-    completion_append = append
+    completion_pos = message.start_pos
+    completion_append = message.append
     for i, match in ipairs(fuzzy_find(line:sub(completion_pos, cursor - 1),
                                       completions)) do
         completion_buffer[i] = completions[match[1]]

player/lua/input.lua

@@ -41,9 +41,13 @@ local function register_event_handler(t)
                 t[type](unpack(utils.parse_json(args or "") or {}))
 
             if type == "complete" and completions then
-                mp.commandv("script-message-to", "console", "complete",
-                            utils.format_json(completions), completion_pos,
-                            completion_append or "")
+                mp.commandv("script-message-to", "console", "complete", utils.format_json({
+                                script_name = mp.get_script_name(),
+                                handler_id = handler_id,
+                                list = completions,
+                                start_pos = completion_pos,
+                                append = completion_append or "",
+                            }))
             end
         end