refactor: remove 'shortmess' save/restore panic for ex commands

This was only used to avoid the effect of SHM_OVERALL. This can easily
be handled in isolation, instead of clearing out all of 'shortmess' which
has unwanted side effects and mystifies what really is going on.

src/nvim/ex_cmds.c

@@ -2689,7 +2689,7 @@ int do_ecmd(int fnum, char *ffname, char *sfname, exarg_T *eap, linenr_T newlnum
 
     // Obey the 'O' flag in 'cpoptions': overwrite any previous file
     // message.
-    if (shortmess(SHM_OVERALL) && !exiting && p_verbose == 0) {
+    if (shortmess(SHM_OVERALL) && !msg_listdo_overwrite && !exiting && p_verbose == 0) {
       msg_scroll = false;
     }
     if (!msg_scroll) {          // wait a bit when overwriting an error msg

src/nvim/ex_cmds2.c

@@ -455,6 +455,10 @@ void ex_listdo(exarg_T *eap)
   tabpage_T *tp;
   char *save_ei = NULL;
 
+  // Temporarily override SHM_OVER and SHM_OVERALL to avoid that file
+  // message overwrites output from the command.
+  msg_listdo_overwrite++;
+
   if (eap->cmdidx != CMD_windo && eap->cmdidx != CMD_tabdo) {
     // Don't do syntax HL autocommands.  Skipping the syntax file is a
     // great speed improvement.
@@ -518,9 +522,7 @@ void ex_listdo(exarg_T *eap)
       if (qf_size == 0 || (size_t)eap->line1 > qf_size) {
         buf = NULL;
       } else {
-        save_clear_shm_value();
         ex_cc(eap);
-        restore_shm_value();
 
         buf = curbuf;
         i = (int)eap->line1 - 1;
@@ -547,9 +549,7 @@ void ex_listdo(exarg_T *eap)
         if (curwin->w_arg_idx != i || !editing_arg_idx(curwin)) {
           // Clear 'shm' to avoid that the file message overwrites
           // any output from the command.
-          save_clear_shm_value();
           do_argfile(eap, i);
-          restore_shm_value();
         }
         if (curwin->w_arg_idx != i) {
           break;
@@ -612,11 +612,8 @@ void ex_listdo(exarg_T *eap)
           break;
         }
 
-        // Go to the next buffer.  Clear 'shm' to avoid that the file
-        // message overwrites any output from the command.
-        save_clear_shm_value();
+        // Go to the next buffer.
         goto_buffer(eap, DOBUF_FIRST, FORWARD, next_fnum);
-        restore_shm_value();
 
         // If autocommands took us elsewhere, quit here.
         if (curbuf->b_fnum != next_fnum) {
@@ -633,11 +630,7 @@ void ex_listdo(exarg_T *eap)
 
         size_t qf_idx = qf_get_cur_idx(eap);
 
-        // Clear 'shm' to avoid that the file message overwrites
-        // any output from the command.
-        save_clear_shm_value();
         ex_cnext(eap);
-        restore_shm_value();
 
         // If jumping to the next quickfix entry fails, quit here.
         if (qf_get_cur_idx(eap) == qf_idx) {
@@ -664,6 +657,7 @@ void ex_listdo(exarg_T *eap)
     listcmd_busy = false;
   }
 
+  msg_listdo_overwrite--;
   if (save_ei != NULL) {
     buf_T *bnext;
     aco_save_T aco;

src/nvim/fileio.c

@@ -105,7 +105,7 @@ void filemess(buf_T *buf, char *name, char *s, int attr)
   // For further ones overwrite the previous one, reset msg_scroll before
   // calling filemess().
   msg_scroll_save = msg_scroll;
-  if (shortmess(SHM_OVERALL) && !exiting && p_verbose == 0) {
+  if (shortmess(SHM_OVERALL) && !msg_listdo_overwrite && !exiting && p_verbose == 0) {
     msg_scroll = false;
   }
   if (!msg_scroll) {    // wait a bit when overwriting an error msg
@@ -316,7 +316,7 @@ int readfile(char *fname, char *sfname, linenr_T from, linenr_T lines_to_skip,
     }
   }
 
-  if ((shortmess(SHM_OVER) || curbuf->b_help) && p_verbose == 0) {
+  if (((shortmess(SHM_OVER) && !msg_listdo_overwrite) || curbuf->b_help) && p_verbose == 0) {
     msg_scroll = false;         // overwrite previous file message
   } else {
     msg_scroll = true;          // don't overwrite previous file message

src/nvim/message.h

@@ -68,6 +68,8 @@ EXTERN int msg_scrolled_at_flush INIT(= 0);
 
 EXTERN int msg_grid_scroll_discount INIT(= 0);
 
+EXTERN int msg_listdo_overwrite INIT(= 0);
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "message.h.generated.h"
 #endif

src/nvim/optionstr.c

@@ -69,8 +69,6 @@ static const char e_backupext_and_patchmode_are_equal[]
   = N_("E589: 'backupext' and 'patchmode' are equal");
 static const char e_showbreak_contains_unprintable_or_wide_character[]
   = N_("E595: 'showbreak' contains unprintable or wide character");
-static const char e_internal_error_shortmess_too_long[]
-  = N_("E1336: Internal error: shortmess too long");
 
 static char *(p_ambw_values[]) = { "single", "double", NULL };
 static char *(p_bg_values[]) = { "light", "dark", NULL };
@@ -2269,36 +2267,6 @@ int check_ff_value(char *p)
   return check_opt_strings(p, p_ff_values, false);
 }
 
-static char shm_buf[SHM_LEN];
-static int set_shm_recursive = 0;
-
-/// Save the actual shortmess Flags and clear them temporarily to avoid that
-/// file messages overwrites any output from the following commands.
-///
-/// Caller must make sure to first call save_clear_shm_value() and then
-/// restore_shm_value() exactly the same number of times.
-void save_clear_shm_value(void)
-{
-  if (strlen(p_shm) >= SHM_LEN) {
-    iemsg(e_internal_error_shortmess_too_long);
-    return;
-  }
-
-  if (++set_shm_recursive == 1) {
-    STRCPY(shm_buf, p_shm);
-    set_option_value_give_err("shm", STATIC_CSTR_AS_OPTVAL(""), 0);
-  }
-}
-
-/// Restore the shortmess Flags set from the save_clear_shm_value() function.
-void restore_shm_value(void)
-{
-  if (--set_shm_recursive == 0) {
-    set_option_value_give_err("shm", CSTR_AS_OPTVAL(shm_buf), 0);
-    memset(shm_buf, 0, SHM_LEN);
-  }
-}
-
 static const char e_conflicts_with_value_of_listchars[]
   = N_("E834: Conflicts with value of 'listchars'");
 static const char e_conflicts_with_value_of_fillchars[]

test/old/testdir/test_autocmd.vim

@@ -3671,7 +3671,7 @@ endfunc
 func SetupVimTest_shm()
   let g:bwe = []
   let g:brp = []
-  set shortmess+=F
+  set shortmess-=l
   messages clear
 
   let dirname='XVimTestSHM'