fix(event-loop): duplicate display updating logic in vgetorpeek() (#17913)

src/nvim/state.c

@@ -15,6 +15,7 @@
 #include "nvim/option.h"
 #include "nvim/option_defs.h"
 #include "nvim/os/input.h"
+#include "nvim/screen.h"
 #include "nvim/state.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
@@ -54,6 +55,12 @@ getkey:
       // Event was made available after the last multiqueue_process_events call
       key = K_EVENT;
     } else {
+      // Duplicate display updating logic in vgetorpeek()
+      if (((State & INSERT) != 0 || p_lz) && (State & CMDLINE) == 0
+          && must_redraw != 0 && !need_wait_return) {
+        update_screen(0);
+        setcursor();  // put cursor back where it belongs
+      }
       // Flush screen updates before blocking
       ui_flush();
       // Call `os_inchar` directly to block for events or user input without

test/functional/api/vim_spec.lua

@@ -1589,6 +1589,18 @@ describe('API', function()
       feed(':digraphs<cr>')
       eq({mode='rm', blocking=true}, nvim("get_mode"))
     end)
+
+    it('after <Nop> mapping returns blocking=false #17257', function()
+      command('nnoremap <F2> <Nop>')
+      feed('<F2>')
+      eq({mode='n', blocking=false}, nvim("get_mode"))
+    end)
+
+    it('after empty string <expr> mapping returns blocking=false #17257', function()
+      command('nnoremap <expr> <F2> ""')
+      feed('<F2>')
+      eq({mode='n', blocking=false}, nvim("get_mode"))
+    end)
   end)
 
   describe('RPC (K_EVENT)', function()

test/functional/ui/input_spec.lua

@@ -320,3 +320,47 @@ describe("event processing and input", function()
     eq({'notification', 'stop', {}}, next_msg())
   end)
 end)
+
+describe('display is updated', function()
+  local screen
+  before_each(function()
+    screen = Screen.new(60, 8)
+    screen:set_default_attr_ids({
+      [1] = {bold = true, foreground = Screen.colors.Blue1},  -- NonText
+      [2] = {bold = true},  -- ModeMsg
+    })
+    screen:attach()
+  end)
+
+  it('in Insert mode after <Nop> mapping #17911', function()
+    command('imap <Plug>test <Nop>')
+    command('imap <F2> abc<CR><Plug>test')
+    feed('i<F2>')
+    screen:expect([[
+      abc                                                         |
+      ^                                                            |
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {2:-- INSERT --}                                                |
+    ]])
+  end)
+
+  it('in Insert mode after empty string <expr> mapping #17911', function()
+    command('imap <expr> <Plug>test ""')
+    command('imap <F2> abc<CR><Plug>test')
+    feed('i<F2>')
+    screen:expect([[
+      abc                                                         |
+      ^                                                            |
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {1:~                                                           }|
+      {2:-- INSERT --}                                                |
+    ]])
+  end)
+end)

test/functional/vimscript/timer_spec.lua

@@ -273,7 +273,7 @@ describe('timers', function()
     eq("Vim(call):E48: Not allowed in sandbox", exc_exec("sandbox call timer_start(0, 'Scary')"))
   end)
 
-  it('can be triggered after an empty string <expr> mapping', function()
+  it('can be triggered after an empty string <expr> mapping #17257', function()
     local screen = Screen.new(40, 6)
     screen:attach()
     command([=[imap <expr> <F2> [timer_start(0, { _ -> execute("throw 'x'", "") }), ''][-1]]=])