fix(multicursor): live-mirror Visual-mode operator mapping #41655

Problem:
Insert entered by a Visual-mode operator mapping (`xnoremap c c`) does
not live-mirror at cursors.

Solution:
Decide `typed` from the Visual session's own provenance (`vatom`, which
spans the selection and knows whether it was user input) instead of only
negating it.

src/nvim/input_cmdatom.c

@@ -77,7 +77,7 @@ static struct {
                       ///< ("f(" + mapped key in one batch). 0: none.
 } composite;
 
-/// State of a Visual composite atom.
+/// State of a Visual session atom.
 typedef enum {
   kVatomNone = 0,   ///< No pending Visual atom.
 
@@ -88,7 +88,10 @@ typedef enum {
   kVatomVoid = 4,   ///< Not replayable: tainted/poisoned (by mouse, gv, …). But may emit CmdAtom.
 } VatomState;
 
-/// Accumulating Visual composite: the full Visual keysequence (selection keys + operator).
+/// Accumulating Visual session atom: the full Visual keysequence (selection keys + operator).
+///
+/// NOTE: Visual session is not modeled as `composite` bc they may overlap (not clean nesting):
+/// a mapping can open before `v` and end mid-selection ("nmap X vjj" followed by "d").
 static struct {
   CmdAtomVec atoms;  ///< Accumulated subatoms. A void session collects them as the `lhs` label.
   VatomState state;
@@ -1147,9 +1150,10 @@ InsSession atom_ins_start(int cmd, long count, VisualIns vis, bool vblock)
                                : cur_frame != NULL ? cur_frame->origin : atom_origin(),
   };
   if (vis != kVInsNone && !mc_replaying()) {
-    if (vis == kVInsKeys && !(atom_visual_replayable() && (vatom.state & kVatomTyped))) {
-      // The selection came from fed keys (":norm", scheduled feedkeys).
-      session.typed = false;
+    if (vis == kVInsKeys) {
+      // Internal (non-user) keys (":norm", scheduled feedkeys) are not user-input.
+      // But a Visual-mode operator mapping ("xnoremap c c") is user-input. #41605
+      session.typed = atom_visual_replayable() && (vatom.state & kVatomTyped) != 0;
     }
     // The selection is consumed: already in the redo body. Also clears selection display.
     atom_visual_reset();

test/functional/editor/mcursor_spec.lua

@@ -1132,7 +1132,7 @@ describe('multicursor', function()
       ]])
     end)
 
-    it('typed text appears at cursors before leaving insert-mode', function()
+    it('typed text live-mirrors at cursors', function()
       local screen = Screen.new(30, 6)
       cursors({ 'aaa', 'bbb', 'ccc' })
       -- Still in insert mode (no <Esc> yet): the text already cascaded; each cursor displays
@@ -1155,8 +1155,7 @@ describe('multicursor', function()
         {1:~                             }|*2
                                       |
       ]])
-      -- Entering insert mode displays each cursor at its insertion point
-      -- right away, BEFORE any text is typed ("a": one char to the right).
+      -- Entering insert mode ("a") displays each cursor at its insertion-point immediately.
       feed('a')
       screen:expect([[
         XY{17:a}aa                         |
@@ -1166,8 +1165,7 @@ describe('multicursor', function()
         {5:-- INSERT --}                  |
       ]])
       feed('<Esc>')
-      -- An operator entry ("ciw") live-mirrors the same way: the entry
-      -- replay changes each cursor's OWN word, still in insert mode.
+      -- Operator entry ("ciw") live-mirrors the per-cursor change, still in insert mode.
       feed('0ciwZ')
       screen:expect([[
         Z{17: }                            |
@@ -1177,8 +1175,7 @@ describe('multicursor', function()
         {5:-- INSERT --}                  |
       ]])
       feed('<Esc>')
-      -- A Visual-entered change ("viwc") live-mirrors too: the entry replay
-      -- re-executes the selection at each cursor.
+      -- Visual-change entry ("viwc") live-mirrors the selection at each cursor.
       feed('viwcW')
       screen:expect([[
         W{17: }                            |
@@ -1188,6 +1185,17 @@ describe('multicursor', function()
         {5:-- INSERT --}                  |
       ]])
       feed('<Esc>')
+      -- Also when "c" is a Visual-mode operator mapping. #41605
+      command('xnoremap c "_c')
+      feed('viwcM')
+      screen:expect([[
+        M{17: }                            |
+        M{17: }                            |
+        M^                             |
+        {1:~                             }|*2
+        {5:-- INSERT --}                  |
+      ]])
+      feed('<Esc>')
     end)
   end)