mp.input: remove race conditions when calling input.terminate()

This commit ensures that `input.terminate()` can only close input
requests made by the same script, and prevents any in-transit events
for old input requests from being processed.

Previously, there was no way to guarantee that the input request being
terminated was the one intended; the asynchronous nature of the API
meant that it was always possible (though unlikely) that another client
may have activated its own input request while the termination request
was in transit.
This commit removes the race condition between different scripts calling
`input.terminate()` by sending the script name alongside the termination
message.

In addition, when a script overwrites one of its own input requests,
there may be incoming events still in transit. Some of these events may
have a decent chance of calling `input.terminate()` if they are
processed (e.g., `submit`). This commit avoids this issue by only
processing `closed` requests once a new `input.get()` request is made.

Author: CogentRedTester

DOCS/man/lua.rst

@@ -976,7 +976,8 @@ REPL.
         script name with ``prompt`` appended.
 
 ``input.terminate()``
-    Close the console.
+    Closes any currently active input request. This will not close
+    requests made by other scripts.
 
 ``input.log(message, style, terminal_style)``
     Add a line to the log buffer. ``style`` can contain additional ASS tags to

player/javascript/defaults.js

@@ -654,12 +654,16 @@ mp.options = { read_options: read_options };
 *  input
 *********************************************************************/
 var input_handle_counter = 1;
+var latest_handler_id
 
 function register_event_handler(t) {
     var handler_id = "input-event/" + input_handle_counter;
     input_handle_counter += 1;
+    latest_handler_id = handler_id
 
     mp.register_script_message(handler_id, function (type, args) {
+        if (latest_handler_id !== handler_id && type !== 'closed') return;
+
         if (t[type]) {
             args = args ? JSON.parse(args) : [];
             var result = t[type].apply(null, args);
@@ -680,13 +684,14 @@ function register_event_handler(t) {
 mp.input = {
     get: function(t) {
         t.has_completions = t.complete !== undefined;
-        var handler_id = register_event_handler(t);
 
         mp.commandv("script-message-to", "console", "get-input",
-                    mp.script_name, handler_id, JSON.stringify(t));
+                    mp.script_name, register_event_handler(t), JSON.stringify(t));
     },
     terminate: function () {
-        mp.commandv("script-message-to", "console", "disable");
+        mp.commandv("script-message-to", "console", "disable", JSON.stringify({
+            script_name: mp.script_name
+        }));
     },
     log: function (message, style, terminal_style) {
         mp.commandv("script-message-to", "console", "log", JSON.stringify({

player/lua/console.lua

@@ -1659,8 +1659,12 @@ set_active = function (active)
     render()
 end
 
-mp.register_script_message("disable", function()
-    set_active(false)
+mp.register_script_message("disable", function(message)
+    message = utils.parse_json(message)
+
+    if not message or message.script_name == input_caller then
+        set_active(false)
+    end
 end)
 
 mp.register_script_message("get-input", function (script_name, handler_id, args)

player/lua/input.lua

@@ -18,6 +18,7 @@ License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
 local utils = require "mp.utils"
 local input = {}
 local handle_counter = 1
+local latest_handler_id
 
 local function get_non_callbacks(t)
     local non_callbacks = {}
@@ -34,8 +35,14 @@ end
 local function register_event_handler(t)
     local handler_id = "input-event/"..handle_counter
     handle_counter = handle_counter + 1
+    latest_handler_id = handler_id
 
     mp.register_script_message(handler_id, function (type, args)
+        -- do not process events (other than closed) for an input that has been overwritten
+        if latest_handler_id ~= handler_id and type ~= 'closed' then
+            return
+        end
+
         if t[type] then
             local completions, completion_pos, completion_append =
                 t[type](unpack(utils.parse_json(args or "") or {}))
@@ -58,15 +65,16 @@ end
 function input.get(t)
     t.has_completions = t.complete ~= nil
 
-    local handler_id = register_event_handler(t)
-    mp.commandv("script-message-to", "console", "get-input",
-                mp.get_script_name(), handler_id, utils.format_json(get_non_callbacks(t)))
+    mp.commandv("script-message-to", "console", "get-input", mp.get_script_name(),
+                register_event_handler(t), utils.format_json(get_non_callbacks(t)))
 end
 
 input.select = input.get
 
 function input.terminate()
-    mp.commandv("script-message-to", "console", "disable")
+    mp.commandv("script-message-to", "console", "disable", utils.format_json({
+        script_name = mp.get_script_name()
+    }))
 end
 
 function input.log(message, style, terminal_style)