vim-patch:9.1.1166: command-line auto-completion hard with wildmenu

Problem:  command-line auto-completion hard with wildmenu
Solution: implement "noselect" wildoption value (Girish Palya)

When `noselect` is present in `wildmode` and 'wildmenu' is enabled, the
completion menu appears without pre-selecting the first item.

This change makes it easier to implement command-line auto-completion,
where the menu dynamically appears as characters are typed, and `<Tab>`
can be used to manually select an item. This can be achieved by
leveraging the `CmdlineChanged` event to insert `wildchar(m)`,
triggering completion menu.

Without this change, auto-completion using the 'wildmenu' mechanism is
not feasible, as it automatically inserts the first match, preventing
dynamic selection.

The following Vimscript snippet demonstrates how to configure
auto-completion using `noselect`:

```vim
vim9script
set wim=noselect:lastused,full wop=pum wcm=<C-@> wmnu
autocmd CmdlineChanged : timer_start(0, function(CmdComplete, [getcmdline()]))

def CmdComplete(cur_cmdline: string, timer: number)
  var [cmdline, curpos] = [getcmdline(), getcmdpos()]
  if cur_cmdline ==# cmdline  # Avoid completing each character in keymaps and pasted text
    && !pumvisible() && curpos == cmdline->len() + 1

    if cmdline[curpos - 2] =~ '[\w*/:]'  # Reduce noise by completing only selected characters
      feedkeys("\<C-@>", "ti")
      set eventignore+=CmdlineChanged  # Suppress redundant completion attempts
      timer_start(0, (_) => {
        getcmdline()->substitute('\%x00$', '', '')->setcmdline()  # Remove <C-@> if no completion items exist
        set eventignore-=CmdlineChanged
      })
    endif
  endif
enddef
```

fixes: vim/vim#16551
closes: vim/vim#16759

https://github.com/vim/vim/commit/2bacc3e5fb3569e0fd98e129cb1e422ca18b80a6

Cherry-pick Wildmode_Tests() change from patch 9.0.0418.

Co-authored-by: Girish Palya <girishji@gmail.com>
Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

4 files changed, 24 insertions, 9 deletions

diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index 33ccc834d2..fcfeda5482 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -288,7 +288,7 @@ int nextwild(expand_T *xp, int type, int options, bool escape)
       p1 = addstar(xp->xp_pattern, xp->xp_pattern_len, xp->xp_context);
     }
     // Translate string into pattern and expand it.
-    const int use_options = (options
+    const int use_options = ((options & ~WILD_KEEP_SOLE_ITEM)
                              | WILD_HOME_REPLACE
                              | WILD_ADD_SLASH
                              | WILD_SILENT
@@ -339,7 +339,7 @@ int nextwild(expand_T *xp, int type, int options, bool escape)
 
   if (xp->xp_numfiles <= 0 && p2 == NULL) {
     beep_flush();
-  } else if (xp->xp_numfiles == 1) {
+  } else if (xp->xp_numfiles == 1 && !(options & WILD_KEEP_SOLE_ITEM)) {
     // free expanded pattern
     ExpandOne(xp, NULL, NULL, 0, WILD_FREE);
   }
diff --git a/src/nvim/cmdexpand.h b/src/nvim/cmdexpand.h
index 33ff787589..59c734e9a3 100644
--- a/src/nvim/cmdexpand.h
+++ b/src/nvim/cmdexpand.h
@@ -40,6 +40,7 @@ enum {
   WILD_NOERROR              = 0x800,  ///< sets EW_NOERROR
   WILD_BUFLASTUSED          = 0x1000,
   BUF_DIFF_FILTER           = 0x2000,
+  WILD_KEEP_SOLE_ITEM       = 0x4000,
 };
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index fc20748309..dbe3505e13 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -1082,6 +1082,9 @@ static int command_line_wildchar_complete(CommandLineState *s)
   if (wim_flags[s->wim_index] & kOptWimFlagLastused) {
     options |= WILD_BUFLASTUSED;
   }
+  if (wim_flags[0] & kOptWimFlagNoselect) {
+    options |= WILD_KEEP_SOLE_ITEM;
+  }
   if (s->xpc.xp_numfiles > 0) {       // typed p_wc at least twice
     // if 'wildmode' contains "list" may still need to list
     if (s->xpc.xp_numfiles > 1
@@ -1124,19 +1127,20 @@ static int command_line_wildchar_complete(CommandLineState *s)
     // when more than one match, and 'wildmode' first contains
     // "list", or no change and 'wildmode' contains "longest,list",
     // list all matches
-    if (res == OK && s->xpc.xp_numfiles > 1) {
+    if (res == OK
+        && s->xpc.xp_numfiles > ((wim_flags[s->wim_index] & kOptWimFlagNoselect) ? 0 : 1)) {
       // a "longest" that didn't do anything is skipped (but not
       // "list:longest")
       if (wim_flags[0] == kOptWimFlagLongest && ccline.cmdpos == j) {
         s->wim_index = 1;
       }
       if ((wim_flags[s->wim_index] & kOptWimFlagList)
-          || (p_wmnu && (wim_flags[s->wim_index] & kOptWimFlagFull) != 0)) {
+          || (p_wmnu && (wim_flags[s->wim_index] & (kOptWimFlagFull|kOptWimFlagNoselect)))) {
         if (!(wim_flags[0] & kOptWimFlagLongest)) {
           int p_wmnu_save = p_wmnu;
           p_wmnu = 0;
           // remove match
-          nextwild(&s->xpc, WILD_PREV, 0, s->firstc != '@');
+          nextwild(&s->xpc, WILD_PREV, 0 | (options & ~kOptWimFlagNoselect), s->firstc != '@');
           p_wmnu = p_wmnu_save;
         }
 
@@ -1146,7 +1150,8 @@ static int command_line_wildchar_complete(CommandLineState *s)
 
         if (wim_flags[s->wim_index] & kOptWimFlagLongest) {
           nextwild(&s->xpc, WILD_LONGEST, options, s->firstc != '@');
-        } else if (wim_flags[s->wim_index] & kOptWimFlagFull) {
+        } else if ((wim_flags[s->wim_index] & kOptWimFlagFull)
+                   && !(wim_flags[s->wim_index] & kOptWimFlagNoselect)) {
           nextwild(&s->xpc, WILD_NEXT, options, s->firstc != '@');
         }
       } else {
@@ -2875,6 +2880,8 @@ int check_opt_wim(void)
       new_wim_flags[idx] |= kOptWimFlagList;
     } else if (i == 8 && strncmp(p, "lastused", 8) == 0) {
       new_wim_flags[idx] |= kOptWimFlagLastused;
+    } else if (i == 8 && strncmp(p, "noselect", 8) == 0) {
+      new_wim_flags[idx] |= kOptWimFlagNoselect;
     } else {
       return FAIL;
     }
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index d1d5a56082..2516d1a970 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -10020,7 +10020,7 @@ local options = {
       cb = 'did_set_wildmode',
       defaults = 'full',
       -- Keep this in sync with check_opt_wim().
-      values = { 'full', 'longest', 'list', 'lastused' },
+      values = { 'full', 'longest', 'list', 'lastused', 'noselect' },
       flags = true,
       deny_duplicates = false,
       desc = [=[
@@ -10042,7 +10042,10 @@ local options = {
         "lastused"	When completing buffer names and more than one buffer
         		matches, sort buffers by time last used (other than
         		the current buffer).
-        When there is only a single match, it is fully completed in all cases.
+        "noselect"	Do not pre-select first menu item and start 'wildmenu'
+        		if it is enabled.
+        When there is only a single match, it is fully completed in all cases
+        except when "noselect" is present.
 
         Examples of useful colon-separated values:
         "longest:full"	Like "longest", but also start 'wildmenu' if it is
@@ -10065,7 +10068,11 @@ local options = {
         	set wildmode=list,full
         <	List all matches without completing, then each full match >vim
         	set wildmode=longest,list
-        <	Complete longest common string, then list alternatives.
+        <	Complete longest common string, then list alternatives >vim
+        	set wildmode=noselect:full
+        <	Display 'wildmenu' without completing, then each full match >vim
+        	set wildmode=noselect:lastused,full
+        <	Same as above, but sort buffers by time last used.
         More info here: |cmdline-completion|.
       ]=],
       full_name = 'wildmode',