feat: ignore swapfile for running Nvim processes #25336

Problem:
The swapfile "E325: ATTENTION" dialog is displayed when editing a file
already open in another (running) Nvim. Usually this behavior is
annoying and irrelevant:
- "Recover" and the other options ("Open readonly", "Quit", "Abort") are
  almost never wanted.
- swapfiles are less relevant for "multi-Nvim" since 'autoread' is
  enabled by default.
  - Even less relevant if user enables 'autowrite'.

Solution:
Define a default SwapExists handler which does the following:
1. If the swapfile is owned by a running Nvim process, automatically
   chooses "(E)dit anyway" (caveat: this creates a new, extra swapfile,
   which is mostly harmless and ignored except by `:recover` or `nvim -r`.
2. Shows a 1-line "ignoring swapfile..." message.
3. Users can disable the default SwapExists handler via `autocmd! nvim_swapfile`.

runtime/doc/autocmd.txt

@@ -118,7 +118,7 @@ manually.  Mostly the screen will not scroll up, thus there is no hit-enter
 prompt.  When one command outputs two messages this can happen anyway.
 
 ==============================================================================
-3. Removing autocommands				*autocmd-remove*
+3. Removing autocommands			*autocmd!* *autocmd-remove*
 
 :au[tocmd]! [group] {event} {aupat} [++once] [++nested] {cmd}
 			Remove all autocommands associated with {event} and

runtime/doc/builtin.txt

@@ -7843,8 +7843,8 @@ swapinfo({fname})                                                   *swapinfo()*
 			user	user name
 			host	host name
 			fname	original file name
-			pid	PID of the Vim process that created the swap
+			pid	PID of the Nvim process that created the swap
-				file
+				file, or zero if not running.
 			mtime	last modification time in seconds
 			inode	Optional: INODE number of the file
 			dirty	1 if file was modified, 0 if not

runtime/doc/editing.txt

@@ -169,33 +169,26 @@ If you want to keep the changed buffer without saving it, switch on the
 2. Editing a file					*edit-a-file*
 
 							*:e* *:edit* *reload*
-:e[dit] [++opt] [+cmd]	Edit the current file.  This is useful to re-edit the
+:e[dit][!] [++opt] [+cmd]
+			Edit the current file.  This is useful to re-edit the
 			current file, when it has been changed outside of Vim.
-			This fails when changes have been made to the current
-			buffer and 'autowriteall' isn't set or the file can't
-			be written.
-			Also see |++opt| and |+cmd|.
-
 							*:edit!* *discard*
-:e[dit]! [++opt] [+cmd]
+			If [!] is given, unsaved changes in the current buffer
-			Edit the current file always.  Discard any changes to
+			are discarded. Without [!] the command fails if there
-			the current buffer.  This is useful if you want to
+			are unsaved changes, unless 'autowriteall' is set and
-			start all over again.
+			the file can be written.
 			Also see |++opt| and |+cmd|.
 
 							*:edit_f*
-:e[dit] [++opt] [+cmd] {file}
+:e[dit][!] [++opt] [+cmd] {file}
 			Edit {file}.
-			This fails when changes have been made to the current
+							*:edit!_f*
-			buffer, unless 'hidden' is set or 'autowriteall' is
+			If [!] is given, unsaved changes in the current buffer
-			set and the file can be written.
+			are discarded. Without [!] the command fails if there
+			are unsaved changes, unless 'hidden' is set or
+			'autowriteall' is set and the file can be written.
 			Also see |++opt| and |+cmd|.
 
-							*:edit!_f*
-:e[dit]! [++opt] [+cmd] {file}
-			Edit {file} always.  Discard any changes to the
-			current buffer.
-			Also see |++opt| and |+cmd|.
 							*:edit_#* *:e#*
 :e[dit] [++opt] [+cmd] #[count]
 			Edit the [count]th buffer (as shown by |:files|).
@@ -1224,10 +1217,10 @@ MULTIPLE WINDOWS AND BUFFERS				*window-exit*
 							*:confirm* *:conf*
 :conf[irm] {command}	Execute {command}, and use a dialog when an
 			operation has to be confirmed.  Can be used on the
-			|:q|, |:qa| and |:w| commands (the latter to override
+			|:edit|, |:q|, |:qa| and |:w| commands (the latter to
-			a read-only setting), and any other command that can
+			override a read-only setting), and any commands that
-			fail in such a way, such as |:only|, |:buffer|,
+			can fail because of unsaved changes, such as |:only|,
-			|:bdelete|, etc.
+			|:buffer|, |:bdelete|, etc.
 
 Examples: >
   :confirm w foo

runtime/doc/eval.txt

@@ -2276,8 +2276,9 @@ v:stderr	|channel-id| corresponding to stderr. The value is always 2;
 			:call chansend(v:stderr, "error: toaster empty\n")
 <
 					*v:swapname* *swapname-variable*
-v:swapname	Only valid when executing |SwapExists| autocommands: Name of
+v:swapname	Name of the swapfile found.
-		the swap file found.  Read-only.
+		Only valid during |SwapExists| event.
+		Read-only.
 
 					*v:swapchoice* *swapchoice-variable*
 v:swapchoice	|SwapExists| autocommands can set this to the selected choice

runtime/doc/news.txt

@@ -114,6 +114,12 @@ The following new APIs and features were added.
 • Builtin TUI can now recognize "super" (|<D-|) and "meta" (|<T-|) modifiers in a
   terminal emulator that supports |tui-csiu|.
 
+• Editor
+  • By default, the swapfile "ATTENTION" |E325| dialog is skipped if the
+    swapfile is owned by a running Nvim process, instead of prompting. If you
+    always want the swapfile dialog, delete the default SwapExists handler:
+    `autocmd! nvim_swapfile`. |default-autocmds|
+
 • LSP
   • LSP method names are available in |vim.lsp.protocol.Methods|.
   • Implemented LSP inlay hints: |vim.lsp.inlay_hint()|

runtime/doc/recover.txt

@@ -83,6 +83,15 @@ Detecting an existing swap file ~
 
 You can find this in the user manual, section |11.3|.
 
+									*W325*
+The default |SwapExists| handler (|default-autocmds|) skips the |E325| prompt
+(selects "(E)dit") if the swapfile owner process (1) is still running and (2)
+was started by the current user.  This presumes that you normally don't want
+to be bothered with the |ATTENTION| message just because you happen to edit
+the same file from multiple Nvim instances.  In the worst case (a system
+crash) there will be more than one swapfile for the file; use |:recover| to
+inspect all of its swapfiles.
+
 
 Updating the swapfile ~
 

runtime/doc/vim_diff.txt

@@ -139,6 +139,11 @@ nvim_terminal:
 nvim_cmdwin:
 - CmdwinEnter: Limits syntax sync to maxlines=1 in the |cmdwin|.
 
+nvim_swapfile:
+- SwapExists: Skips the swapfile prompt (sets |v:swapchoice| to "e") when the
+  swapfile is owned by a running Nvim process. Shows |W325| "Ignoring
+  swapfile…" message.
+
 ==============================================================================
 New Features						       *nvim-features*
 

runtime/lua/vim/_editor.lua

@@ -1147,11 +1147,28 @@ function vim._init_default_autocmds()
       end
     end,
   })
+
   vim.api.nvim_create_autocmd({ 'CmdwinEnter' }, {
     pattern = '[:>]',
     group = vim.api.nvim_create_augroup('nvim_cmdwin', {}),
     command = 'syntax sync minlines=1 maxlines=1',
   })
+
+  vim.api.nvim_create_autocmd({ 'SwapExists' }, {
+    pattern = '*',
+    group = vim.api.nvim_create_augroup('nvim_swapfile', {}),
+    callback = function()
+      local info = vim.fn.swapinfo(vim.v.swapname)
+      local user = vim.uv.os_get_passwd().username
+      local iswin = 1 == vim.fn.has('win32')
+      if info.error or info.pid <= 0 or (not iswin and info.user ~= user) then
+        vim.v.swapchoice = '' -- Show the prompt.
+        return
+      end
+      vim.v.swapchoice = 'e' -- Choose "(E)dit".
+      vim.notify(('W325: Ignoring swapfile from Nvim process %d'):format(info.pid))
+    end,
+  })
 end
 
 function vim._init_defaults()

runtime/lua/vim/_meta/vimfn.lua

@@ -9312,8 +9312,8 @@ function vim.fn.swapfilelist() end
 ---   user  user name
 ---   host  host name
 ---   fname  original file name
----   pid  PID of the Vim process that created the swap
+---   pid  PID of the Nvim process that created the swap
----     file
+---     file, or zero if not running.
 ---   mtime  last modification time in seconds
 ---   inode  Optional: INODE number of the file
 ---   dirty  1 if file was modified, 0 if not

src/nvim/eval.lua

@@ -11123,8 +11123,8 @@ M.funcs = {
       	user	user name
       	host	host name
       	fname	original file name
-      	pid	PID of the Vim process that created the swap
+      	pid	PID of the Nvim process that created the swap
-      		file
+      		file, or zero if not running.
       	mtime	last modification time in seconds
       	inode	Optional: INODE number of the file
       	dirty	1 if file was modified, 0 if not

src/nvim/eval/funcs.c

@@ -8236,7 +8236,7 @@ static void f_swapfilelist(typval_T *argvars, typval_T *rettv, EvalFuncData fptr
 static void f_swapinfo(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
   tv_dict_alloc_ret(rettv);
-  get_b0_dict(tv_get_string(argvars), rettv->vval.v_dict);
+  swapfile_dict(tv_get_string(argvars), rettv->vval.v_dict);
 }
 
 /// "swapname(expr)" function

src/nvim/eval/userfunc.c

@@ -2491,7 +2491,7 @@ void ex_function(exarg_T *eap)
         } else if (line_arg != NULL && *skipwhite(line_arg) != NUL) {
           nextcmd = line_arg;
         } else if (*p != NUL && *p != '"' && p_verbose > 0) {
-          give_warning2(_("W22: Text found after :endfunction: %s"), p, true);
+          swmsg(true, _("W22: Text found after :endfunction: %s"), p);
         }
         if (nextcmd != NULL) {
           // Another command follows. If the line came from "eap" we

src/nvim/memline.c

@@ -168,11 +168,9 @@ enum {
   B0_MAGIC_CHAR = 0x55,
 };
 
-// Block zero holds all info about the swap file. This is the first block in
+// Block zero holds all info about the swapfile. This is the first block in the file.
-// the file.
 //
-// NOTE: DEFINITION OF BLOCK 0 SHOULD NOT CHANGE! It would make all existing
+// NOTE: DEFINITION OF BLOCK 0 SHOULD NOT CHANGE! It would make all existing swapfiles unusable!
-// swap files unusable!
 //
 // If size of block0 changes anyway, adjust MIN_SWAP_PAGE_SIZE in vim.h!!
 //
@@ -210,8 +208,7 @@ typedef struct {
 // EOL_MAC + 1.
 #define B0_FF_MASK      3
 
-// Swap file is in directory of edited file.  Used to find the file from
+// Swapfile is in directory of edited file.  Used to find the file from different mount points.
-// different mount points.
 #define B0_SAME_DIR     4
 
 // The 'fileencoding' is at the end of b0_fname[], with a NUL in front of it.
@@ -724,10 +721,13 @@ static void add_b0_fenc(ZeroBlock *b0p, buf_T *buf)
   }
 }
 
-/// Return true if the process with number "b0p->b0_pid" is still running.
+/// Returns the PID of the process that owns the swapfile, if it is running.
-/// "swap_fname" is the name of the swap file, if it's from before a reboot then
+///
-/// the result is false;
+/// @param b0p swapfile data
-static bool swapfile_process_running(const ZeroBlock *b0p, const char *swap_fname)
+/// @param swap_fname Name of the swapfile. If it's from before a reboot, the result is 0.
+///
+/// @return PID, or 0 if process is not running or the swapfile is from before a reboot.
+static int swapfile_process_running(const ZeroBlock *b0p, const char *swap_fname)
 {
   FileInfo st;
   double uptime;
@@ -736,15 +736,15 @@ static bool swapfile_process_running(const ZeroBlock *b0p, const char *swap_fnam
   if (os_fileinfo(swap_fname, &st)
       && uv_uptime(&uptime) == 0
       && (Timestamp)st.stat.st_mtim.tv_sec < os_time() - (Timestamp)uptime) {
-    return false;
+    return 0;
   }
-  return os_proc_running((int)char_to_long(b0p->b0_pid));
+  int pid = (int)char_to_long(b0p->b0_pid);
+  return os_proc_running(pid) ? pid : 0;
 }
 
 /// Try to recover curbuf from the .swp file.
 ///
-/// @param checkext  if true, check the extension and detect whether it is a
+/// @param checkext  if true, check the extension and detect whether it is a swapfile.
-///                  swap file.
 void ml_recover(bool checkext)
 {
   buf_T *buf = NULL;
@@ -1456,12 +1456,13 @@ char *make_percent_swname(const char *dir, const char *name)
   return d;
 }
 
-static bool process_still_running;
+// PID of swapfile owner, or zero if not running.
+static int process_running;
 
-/// This is used by the swapinfo() function.
+/// For Vimscript "swapinfo()".
 ///
 /// @return  information found in swapfile "fname" in dictionary "d".
-void get_b0_dict(const char *fname, dict_T *d)
+void swapfile_dict(const char *fname, dict_T *d)
 {
   int fd;
   ZeroBlock b0;
@@ -1482,7 +1483,7 @@ void get_b0_dict(const char *fname, dict_T *d)
         tv_dict_add_str_len(d, S_LEN("fname"), b0.b0_fname,
                             B0_FNAME_SIZE_ORG);
 
-        tv_dict_add_nr(d, S_LEN("pid"), char_to_long(b0.b0_pid));
+        tv_dict_add_nr(d, S_LEN("pid"), swapfile_process_running(&b0, fname));
         tv_dict_add_nr(d, S_LEN("mtime"), char_to_long(b0.b0_mtime));
         tv_dict_add_nr(d, S_LEN("dirty"), b0.b0_dirty ? 1 : 0);
         tv_dict_add_nr(d, S_LEN("inode"), char_to_long(b0.b0_ino));
@@ -1496,7 +1497,7 @@ void get_b0_dict(const char *fname, dict_T *d)
   }
 }
 
-/// Give information about an existing swap file.
+/// Loads info from swapfile `fname`, and displays it to the user.
 ///
 /// @return  timestamp (0 when unknown).
 static time_t swapfile_info(char *fname)
@@ -1567,9 +1568,8 @@ static time_t swapfile_info(char *fname)
         if (char_to_long(b0.b0_pid) != 0L) {
           msg_puts(_("\n        process ID: "));
           msg_outnum((int)char_to_long(b0.b0_pid));
-          if (swapfile_process_running(&b0, fname)) {
+          if ((process_running = swapfile_process_running(&b0, fname))) {
             msg_puts(_(" (STILL RUNNING)"));
-            process_still_running = true;
           }
         }
 
@@ -1589,8 +1589,7 @@ static time_t swapfile_info(char *fname)
   return x;
 }
 
-/// @return  true if the swap file looks OK and there are no changes, thus it
+/// @return  true if the swapfile looks OK and there are no changes, thus it can be safely deleted.
-///          can be safely deleted.
 static bool swapfile_unchanged(char *fname)
 {
   ZeroBlock b0;
@@ -3175,13 +3174,10 @@ char *makeswapname(char *fname, char *ffname, buf_T *buf, char *dir_name)
 }
 
 /// Get file name to use for swapfile or backup file.
-/// Use the name of the edited file "fname" and an entry in the 'dir' or 'bdir'
+/// Use the name of the edited file "fname" and an entry in the 'dir' or 'bdir' option "dname".
-/// option "dname".
 /// - If "dname" is ".", return "fname" (swapfile in dir of file).
-/// - If "dname" starts with "./", insert "dname" in "fname" (swap file
+/// - If "dname" starts with "./", insert "dname" in "fname" (swapfile relative to dir of file).
-///   relative to dir of file).
+/// - Otherwise, prepend "dname" to the tail of "fname" (swapfile in specific dir).
-/// - Otherwise, prepend "dname" to the tail of "fname" (swap file in specific
-///   dir).
 ///
 /// The return value is an allocated string and can be NULL.
 ///
@@ -3333,7 +3329,7 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
   char *dir_name = xmalloc(dir_len);
   (void)copy_option_part(dirp, dir_name, dir_len, ",");
 
-  // we try different names until we find one that does not exist yet
+  // We try different swapfile names until we find one that does not exist yet.
   char *fname = makeswapname(buf_fname, buf->b_ffname, buf, dir_name);
 
   while (true) {
@@ -3365,17 +3361,17 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
       // Give an error message, unless recovering, no file name, we are
       // viewing a help file or when the path of the file is different
       // (happens when all .swp files are in one directory).
-      if (!recoverymode && buf_fname != NULL
+      if (!recoverymode && buf_fname != NULL && !buf->b_help && !(buf->b_flags & BF_DUMMY)) {
-          && !buf->b_help && !(buf->b_flags & BF_DUMMY)) {
         int fd;
         ZeroBlock b0;
         int differ = false;
 
-        // Try to read block 0 from the swap file to get the original
+        // Try to read block 0 from the swapfile to get the original file name (and inode number).
-        // file name (and inode number).
         fd = os_open(fname, O_RDONLY, 0);
         if (fd >= 0) {
           if (read_eintr(fd, &b0, sizeof(b0)) == sizeof(b0)) {
+            process_running = swapfile_process_running(&b0, fname);
+
             // If the swapfile has the same directory as the
             // buffer don't compare the directory names, they can
             // have a different mountpoint.
@@ -3393,8 +3389,7 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
                 }
               }
             } else {
-              // The name in the swap file may be
+              // The name in the swapfile may be "~user/path/file".  Expand it first.
-              // "~user/path/file".  Expand it first.
               expand_env(b0.b0_fname, NameBuff, MAXPATHL);
               if (fnamecmp_ino(buf->b_ffname, NameBuff,
                                char_to_long(b0.b0_ino))) {
@@ -3405,13 +3400,13 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
           close(fd);
         }
 
-        // give the ATTENTION message when there is an old swap file
+        // Show the ATTENTION message when:
-        // for the current file, and the buffer was not recovered.
+        //  - there is an old swapfile for the current file
+        //  - the buffer was not recovered
         if (differ == false && !(curbuf->b_flags & BF_RECOVERED)
             && vim_strchr(p_shm, SHM_ATTENTION) == NULL) {
           int choice = 0;
 
-          process_still_running = false;
           // It's safe to delete the swapfile if all these are true:
           // - the edited file exists
           // - the swapfile has no changes and looks OK
@@ -3430,6 +3425,7 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
             choice = do_swapexists(buf, fname);
           }
 
+          process_running = 0;  // Set by attention_message..swapfile_info.
           if (choice == 0) {
             // Show info about the existing swapfile.
             attention_message(buf, fname);
@@ -3459,14 +3455,14 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
             xstrlcat(name, sw_msg_2, name_len);
             choice = do_dialog(VIM_WARNING, _("VIM - ATTENTION"),
                                name,
-                               process_still_running
+                               process_running
                                ? _("&Open Read-Only\n&Edit anyway\n&Recover"
                                    "\n&Quit\n&Abort") :
                                _("&Open Read-Only\n&Edit anyway\n&Recover"
                                  "\n&Delete it\n&Quit\n&Abort"),
                                1, NULL, false);
 
-            if (process_still_running && choice >= 4) {
+            if (process_running && choice >= 4) {
               choice++;  // Skip missing "Delete it" button.
             }
             xfree(name);
@@ -3477,27 +3473,27 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
 
           if (choice > 0) {
             switch (choice) {
-            case 1:
+            case 1:  // "Open Read-Only"
               buf->b_p_ro = true;
               break;
-            case 2:
+            case 2:  // "Edit anyway"
               break;
-            case 3:
+            case 3:  // "Recover"
               swap_exists_action = SEA_RECOVER;
               break;
-            case 4:
+            case 4:  // "Delete it"
               os_remove(fname);
               break;
-            case 5:
+            case 5:  // "Quit"
               swap_exists_action = SEA_QUIT;
               break;
-            case 6:
+            case 6:  // "Abort"
               swap_exists_action = SEA_QUIT;
               got_int = true;
               break;
             }
 
-            // If the file was deleted this fname can be used.
+            // If the swapfile was deleted this `fname` can be used.
             if (!os_path_exists(fname)) {
               break;
             }
@@ -3512,10 +3508,10 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname, bool *found_
       }
     }
 
-    // Change the ".swp" extension to find another file that can be used.
+    // Permute the ".swp" extension to find a unique swapfile name.
     // First decrement the last char: ".swo", ".swn", etc.
     // If that still isn't enough decrement the last but one char: ".svz"
-    // Can happen when editing many "No Name" buffers.
+    // Can happen when many Nvim instances are editing the same file (including "No Name" buffers).
     if (fname[n - 1] == 'a') {          // ".s?a"
       if (fname[n - 2] == 'a') {        // ".saa": tried enough, give up
         emsg(_("E326: Too many swap files found"));

src/nvim/message.c

@@ -475,7 +475,14 @@ void trunc_string(const char *s, char *buf, int room_in, int buflen)
   }
 }
 
-// Note: Caller of smsg() must check the resulting string is shorter than IOSIZE!!!
+/// Shows a printf-style message with attributes.
+///
+/// Note: Caller must check the resulting string is shorter than IOSIZE!!!
+///
+/// @see semsg
+/// @see swmsg
+///
+/// @param s printf-style format message
 int smsg(int attr, const char *s, ...)
   FUNC_ATTR_PRINTF(2, 3)
 {
@@ -757,6 +764,8 @@ void emsg_invreg(int name)
 }
 
 /// Print an error message with unknown number of arguments
+///
+/// @return whether the message was displayed
 bool semsg(const char *const fmt, ...)
   FUNC_ATTR_PRINTF(1, 2)
 {
@@ -3337,9 +3346,22 @@ void give_warning(const char *message, bool hl)
   no_wait_return--;
 }
 
-void give_warning2(const char *const message, const char *const a1, bool hl)
+/// Shows a warning, with optional highlighting.
+///
+/// @param hl enable highlighting
+/// @param fmt printf-style format message
+///
+/// @see smsg
+/// @see semsg
+void swmsg(bool hl, const char *const fmt, ...)
+  FUNC_ATTR_PRINTF(2, 3)
 {
-  vim_snprintf(IObuff, IOSIZE, message, a1);
+  va_list args;
+
+  va_start(args, fmt);
+  vim_vsnprintf(IObuff, IOSIZE, fmt, args);
+  va_end(args);
+
   give_warning(IObuff, hl);
 }
 

test/functional/ex_cmds/swapfile_preserve_recover_spec.lua

@@ -171,6 +171,7 @@ describe('swapfile detection', function()
     local screen2 = Screen.new(256, 40)
     screen2:attach()
     exec(init)
+    command('autocmd! nvim_swapfile')  -- Delete the default handler (which skips the dialog).
 
     -- With shortmess+=F
     command('set shortmess+=F')
@@ -219,11 +220,29 @@ describe('swapfile detection', function()
     nvim2:close()
   end)
 
+  it('default SwapExists handler selects "(E)dit" and skips prompt', function()
+    exec(init)
+    command('edit Xfile1')
+    command("put ='some text...'")
+    command('preserve')  -- Make sure the swap file exists.
+    local nvimpid = funcs.getpid()
+
+    local nvim1 = spawn(new_argv(), true, nil, true)
+    set_session(nvim1)
+    local screen = Screen.new(75, 18)
+    screen:attach()
+    exec(init)
+    feed(':edit Xfile1\n')
+
+    screen:expect({ any = ('W325: Ignoring swapfile from Nvim process %d'):format(nvimpid) })
+    nvim1:close()
+  end)
+
   -- oldtest: Test_swap_prompt_splitwin()
   it('selecting "q" in the attention prompt', function()
     exec(init)
     command('edit Xfile1')
-    command('preserve')  -- should help to make sure the swap file exists
+    command('preserve')  -- Make sure the swap file exists.
 
     local screen = Screen.new(75, 18)
     screen:set_default_attr_ids({
@@ -235,7 +254,9 @@ describe('swapfile detection', function()
     set_session(nvim1)
     screen:attach()
     exec(init)
+    command('autocmd! nvim_swapfile')  -- Delete the default handler (which skips the dialog).
     feed(':split Xfile1\n')
+    -- The default SwapExists handler does _not_ skip this prompt.
     screen:expect({
       any = pesc('{1:[O]pen Read-Only, (E)dit anyway, (R)ecover, (Q)uit, (A)bort: }^')
     })
@@ -267,6 +288,7 @@ describe('swapfile detection', function()
     set_session(nvim2)
     screen:attach()
     exec(init)
+    command('autocmd! nvim_swapfile')  -- Delete the default handler (which skips the dialog).
     command('set more')
     command('au bufadd * let foo_w = wincol()')
     feed(':e Xfile1<CR>')
@@ -300,8 +322,9 @@ describe('swapfile detection', function()
     nvim2:close()
   end)
 
-  -- oldtest: Test_nocatch_process_still_running()
+  --- @param swapexists boolean Enable the default SwapExists handler.
-  it('allows deleting swapfile created before boot vim-patch:8.2.2586', function()
+  --- @param on_swapfile_running fun(screen: any) Called after swapfile ("STILL RUNNING") prompt.
+  local function test_swapfile_after_reboot(swapexists, on_swapfile_running)
     local screen = Screen.new(75, 30)
     screen:set_default_attr_ids({
       [0] = {bold = true, foreground = Screen.colors.Blue},  -- NonText
@@ -311,6 +334,9 @@ describe('swapfile detection', function()
     screen:attach()
 
     exec(init)
+    if not swapexists then
+      command('autocmd! nvim_swapfile')  -- Delete the default handler (which skips the dialog).
+    end
     command('set nohidden')
 
     exec([=[
@@ -347,12 +373,7 @@ describe('swapfile detection', function()
     os.rename('Xswap', swname)
 
     feed(':edit Xswaptest<CR>')
-    screen:expect({any = table.concat({
+    on_swapfile_running(screen)
-      pesc('{2:E325: ATTENTION}'),
-      'file name: .*Xswaptest',
-      'process ID: %d* %(STILL RUNNING%)',
-      pesc('{1:[O]pen Read-Only, (E)dit anyway, (R)ecover, (Q)uit, (A)bort: }^'),
-    }, '.*')})
 
     feed('e')
 
@@ -374,9 +395,28 @@ describe('swapfile detection', function()
     }, '.*')})
 
     feed('e')
+  end
+
+  -- oldtest: Test_nocatch_process_still_running()
+  it('swapfile created before boot vim-patch:8.2.2586', function()
+    test_swapfile_after_reboot(false, function(screen)
+      screen:expect({any = table.concat({
+        pesc('{2:E325: ATTENTION}'),
+        'file name: .*Xswaptest',
+        'process ID: %d* %(STILL RUNNING%)',
+        pesc('{1:[O]pen Read-Only, (E)dit anyway, (R)ecover, (Q)uit, (A)bort: }^'),
+      }, '.*')})
     end)
   end)
 
+  it('swapfile created before boot + default SwapExists handler', function()
+    test_swapfile_after_reboot(true, function(screen)
+      screen:expect({ any = 'W325: Ignoring swapfile from Nvim process' })
+    end)
+  end)
+
+end)
+
 describe('quitting swapfile dialog on startup stops TUI properly', function()
   local swapdir = luv.cwd()..'/Xtest_swapquit_dir'
   local testfile = 'Xtest_swapquit_file1'