Update commandline state snapshot lazily

I think commit 8386088b3 (Update commandline state changes eagerly as well,
2024-04-11) broke the alt-s binding.

This is because we update the commandline state snapshot (which is consumed
by builtin commandline and others) only at key points.  This seems like a
dubious optimization.  With the new streamlined bind execution semantics,
this doesn't really work anymore; any shell command can run any number of
commands like "commandline -i foo" which should synchronize.

Do the simple thing of calculating the snapshot whenever needed.

src/builtins/commandline.rs

@@ -181,7 +181,7 @@ fn write_part(
 
 /// The commandline builtin. It is used for specifying a new value for the commandline.
 pub fn commandline(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Option<c_int> {
-    let rstate = commandline_get_state();
+    let rstate = commandline_get_state(true);
 
     let mut buffer_part = None;
     let mut cut_at_cursor = false;

src/builtins/complete.rs

@@ -485,7 +485,7 @@ pub fn complete(parser: &Parser, streams: &mut IoStreams, argv: &mut [&wstr]) ->
         let do_complete_param = match do_complete_param {
             None => {
                 // No argument given, try to use the current commandline.
-                let commandline_state = commandline_get_state();
+                let commandline_state = commandline_get_state(true);
                 if !commandline_state.initialized {
                     // This corresponds to using 'complete -C' in non-interactive mode.
                     // See #2361    .

src/builtins/history.rs

@@ -243,7 +243,7 @@ pub fn history(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) ->
 
     // Use the default history if we have none (which happens if invoked non-interactively, e.g.
     // from webconfig.py.
-    let history = commandline_get_state()
+    let history = commandline_get_state(true)
         .history
         .unwrap_or_else(|| History::with_name(&history_session_id(parser.vars())));
 

src/env/environment_impl.rs

@@ -353,7 +353,7 @@ impl EnvScopedImpl {
             if !is_main_thread() {
                 return None;
             }
-            let history = commandline_get_state().history.unwrap_or_else(|| {
+            let history = commandline_get_state(true).history.unwrap_or_else(|| {
                 let fish_history_var = self.getf(L!("fish_history"), EnvMode::default());
                 let session_id = history_session_id_from_var(fish_history_var);
                 History::with_name(&session_id)

src/reader.rs

@@ -156,8 +156,8 @@ static INTERRUPTED: AtomicI32 = AtomicI32::new(0);
 /// This is set from a signal handler.
 static SIGHUP_RECEIVED: RelaxedAtomicBool = RelaxedAtomicBool::new(false);
 
-/// A singleton snapshot of the reader state. This is updated when the reader changes. This is
+/// A singleton snapshot of the reader state. This is factored out for thread-safety reasons:
-/// factored out for thread-safety reasons: it may be fetched on a background thread.
+/// it may be fetched on a background thread.
 fn commandline_state_snapshot() -> MutexGuard<'static, CommandlineState> {
     static STATE: Mutex<CommandlineState> = Mutex::new(CommandlineState::new());
     STATE.lock().unwrap()
@@ -233,7 +233,6 @@ fn reader_push_ret(
     if reader_data_stack().len() == 1 {
         reader_interactive_init(parser);
     }
-    data.update_commandline_state();
     data
 }
 
@@ -252,7 +251,6 @@ pub fn reader_pop() {
         new_reader
             .screen
             .reset_abandoning_line(usize::try_from(termsize_last().width).unwrap());
-        new_reader.update_commandline_state();
     } else {
         reader_interactive_destroy();
         *commandline_state_snapshot() = CommandlineState::new();
@@ -907,7 +905,6 @@ pub fn reader_execute_readline_cmd(ch: CharEvent) {
         }
         data.save_screen_state();
         data.handle_char_event(Some(ch));
-        data.update_commandline_state();
     }
 }
 
@@ -940,7 +937,10 @@ pub fn reader_readline(nchars: usize) -> Option<WString> {
 }
 
 /// Get the command line state. This may be fetched on a background thread.
-pub fn commandline_get_state() -> CommandlineState {
+pub fn commandline_get_state(sync: bool) -> CommandlineState {
+    if sync {
+        current_data().map(|data| data.update_commandline_state());
+    }
     commandline_state_snapshot().clone()
 }
 
@@ -1182,27 +1182,34 @@ impl ReaderData {
                 self.pager_selection_changed();
             }
         }
-        // Ensure that the commandline builtin sees our new state.
-        self.update_commandline_state();
     }
 
     /// Reflect our current data in the command line state snapshot.
-    /// This is called before we run any fish script, so that the commandline builtin can see our
-    /// state.
     fn update_commandline_state(&self) {
         let mut snapshot = commandline_state_snapshot();
-        snapshot.text = self.command_line.text().to_owned();
+        if snapshot.text != self.command_line.text() {
+            snapshot.text = self.command_line.text().to_owned();
+        }
         snapshot.cursor_pos = self.command_line.position();
         snapshot.history = Some(self.history.clone());
         snapshot.selection = self.get_selection();
         snapshot.pager_mode = !self.pager.is_empty();
         snapshot.pager_fully_disclosed = self.current_page_rendering.remaining_to_disclose == 0;
-        snapshot.search_field = self.pager.search_field_shown.then(|| {
+        if snapshot
-            (
+            .search_field
-                self.pager.search_field_line.text().to_owned(),
+            .as_ref()
-                self.pager.search_field_line.position(),
+            .is_none_or(|(text, position)| {
-            )
+                text != self.pager.search_field_line.text()
-        });
+                    || *position != self.pager.search_field_line.position()
+            })
+        {
+            snapshot.search_field = self.pager.search_field_shown.then(|| {
+                (
+                    self.pager.search_field_line.text().to_owned(),
+                    self.pager.search_field_line.position(),
+                )
+            });
+        }
         snapshot.search_mode = self.history_search.active();
         snapshot.initialized = true;
     }
@@ -1211,7 +1218,7 @@ impl ReaderData {
     /// incorporating changes from the commandline builtin.
     fn apply_commandline_state_changes(&mut self) {
         // Only the text and cursor position may be changed.
-        let state = commandline_get_state();
+        let state = commandline_get_state(false);
         if state.text != self.command_line.text()
             || state.cursor_pos != self.command_line.position()
         {
@@ -1904,7 +1911,6 @@ impl ReaderData {
 
     /// Run a sequence of commands from an input binding.
     fn run_input_command_scripts(&mut self, cmd: &wstr) {
-        self.update_commandline_state();
         self.eval_bind_cmd(cmd);
 
         // Restore tty to shell modes.
@@ -4554,7 +4560,6 @@ impl ReaderData {
         let (elt, el) = self.active_edit_line();
         if self.conf.expand_abbrev_ok && elt == EditableLineTag::Commandline {
             // Try expanding abbreviations.
-            self.update_commandline_state();
             let cursor_pos = el.position().saturating_sub(cursor_backtrack);
             if let Some(replacement) =
                 reader_expand_abbreviation_at_cursor(el.text(), cursor_pos, self.parser())
@@ -5284,9 +5289,6 @@ impl ReaderData {
         // up to the end of the token we're completing.
         let cmdsub = &el.text()[cmdsub_range.start..token_range.end];
 
-        // Ensure that `commandline` inside the completions gets the current state.
-        self.update_commandline_state();
-
         let (comp, _needs_load) = complete(
             cmdsub,
             CompletionRequestOptions::normal(),

tests/checks/tmux-bind2.fish

@@ -0,0 +1,13 @@
+#RUN: %fish %s
+#REQUIRES: command -v tmux
+
+isolated-tmux-start
+
+isolated-tmux send-keys "function prepend; commandline --cursor 0; commandline -i echo; end" Enter
+isolated-tmux send-keys "bind c-g prepend" Enter
+isolated-tmux send-keys C-l
+isolated-tmux send-keys 'printf'
+isolated-tmux send-keys C-g Space
+tmux-sleep
+isolated-tmux capture-pane -p
+# CHECK: prompt 2> echo printf