feat(completion): support completing more string options

runtime/doc/news.txt

@@ -105,6 +105,8 @@ The following new APIs and features were added.
 
 • |nvim_set_keymap()| and |nvim_del_keymap()| now support abbreviations.
 
+• Better cmdline completion for string option value. |complete-set-option|
+
 • Builtin TUI can now recognize "super" (|<D-|) and "meta" (|<T-|) modifiers in a
   terminal emulator that supports |tui-csiu|.
 

runtime/doc/vim_diff.txt

@@ -287,13 +287,12 @@ Options:
   'diffopt'     "linematch" feature
   'exrc'        searches for ".nvim.lua", ".nvimrc", or ".exrc" files. The
                 user is prompted whether to trust the file.
-  'fillchars'   flags: "msgsep", "horiz", "horizup",
-                "horizdown", "vertleft", "vertright", "verthoriz"
+  'fillchars'   flags: "msgsep", "horiz", "horizup", "horizdown",
+                "vertleft", "vertright", "verthoriz"
   'foldcolumn'  supports up to 9 dynamic/fixed columns
   'guicursor'   works in the terminal (TUI)
   'inccommand'  shows interactive results for |:substitute|-like commands
                 and |:command-preview| commands
-  'jumpoptions' "stack" behavior
   'jumpoptions' "view" tries to restore the |mark-view| when moving through
   the |jumplist|, |changelist|, |alternate-file| or using |mark-motions|.
   'laststatus'  global statusline support
@@ -304,6 +303,7 @@ Options:
   'signcolumn'  supports up to 9 dynamic/fixed columns
   'statuscolumn' full control of columns using 'statusline' format
   'tabline'     %@Func@foo%X can call any function on mouse-click
+  'termpastefilter'
   'ttimeout', 'ttimeoutlen' behavior was simplified
   'winblend'    pseudo-transparency in floating windows |api-floatwin|
   'winhighlight' window-local highlights
@@ -382,6 +382,7 @@ Upstreamed features					 *nvim-upstreamed*
 These Nvim features were later integrated into Vim.
 
 - 'fillchars' flags: "eob"
+- 'jumpoptions' "stack" behavior
 - 'wildoptions' flags: "pum" enables popupmenu for wildmode completion
 - |<Cmd>|
 - |WinClosed|

src/nvim/cmdexpand.c

@@ -2598,7 +2598,7 @@ static int ExpandOther(char *pat, expand_T *xp, regmatch_T *rmp, char ***matches
     { EXPAND_MENUNAMES, get_menu_names, false, true },
     { EXPAND_SYNTAX, get_syntax_name, true, true },
     { EXPAND_SYNTIME, get_syntime_arg, true, true },
-    { EXPAND_HIGHLIGHT, (ExpandFunc)get_highlight_name, true, false },
+    { EXPAND_HIGHLIGHT, get_highlight_name, true, false },
     { EXPAND_EVENTS, expand_get_event_name, true, false },
     { EXPAND_AUGROUP, expand_get_augroup_name, true, false },
     { EXPAND_SIGN, get_sign_name, true, true },

src/nvim/highlight_group.c

@@ -2283,10 +2283,10 @@ static void highlight_list_two(int cnt, int attr)
 }
 
 /// Function given to ExpandGeneric() to obtain the list of group names.
-const char *get_highlight_name(expand_T *const xp, int idx)
+char *get_highlight_name(expand_T *const xp, int idx)
   FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  return get_highlight_name_ext(xp, idx, true);
+  return (char *)get_highlight_name_ext(xp, idx, true);
 }
 
 /// Obtain a highlight group name.

src/nvim/options.lua

@@ -2935,6 +2935,7 @@ return {
             "[1-9]":      to display a fixed number of columns
         See |folding|.
       ]=],
+      expand_cb = 'expand_set_foldcolumn',
       full_name = 'foldcolumn',
       redraw = { 'current_window' },
       scope = { 'window' },
@@ -4082,6 +4083,7 @@ return {
         'redrawtime') then 'inccommand' is automatically disabled until
         |Command-line-mode| is done.
       ]=],
+      expand_cb = 'expand_set_inccommand',
       full_name = 'inccommand',
       scope = { 'global' },
       short_desc = N_('Live preview of substitution'),
@@ -5552,6 +5554,7 @@ return {
         <	Will make Nvim scroll 5 lines at a time when scrolling vertically, and
         scroll 2 columns at a time when scrolling horizontally.
       ]=],
+      expand_cb = 'expand_set_mousescroll',
       full_name = 'mousescroll',
       list = 'comma',
       scope = { 'global' },
@@ -8780,6 +8783,7 @@ return {
 
            C1	    Control characters 0x80...0x9F
       ]=],
+      expand_cb = 'expand_set_termpastefilter',
       full_name = 'termpastefilter',
       list = 'onecomma',
       scope = { 'global' },
@@ -9749,7 +9753,7 @@ return {
     {
       abbreviation = 'winhl',
       alloced = true,
-      cb = 'did_set_winhl',
+      cb = 'did_set_winhighlight',
       defaults = { if_true = '' },
       deny_duplicates = true,
       desc = [=[
@@ -9771,8 +9775,9 @@ return {
         	set winhighlight=Normal:MyNormal,NormalNC:MyNormalNC
         <
       ]=],
+      expand_cb = 'expand_set_winhighlight',
       full_name = 'winhighlight',
-      list = 'onecomma',
+      list = 'onecommacolon',
       redraw = { 'current_window' },
       scope = { 'window' },
       short_desc = N_('Setup window-local highlights'),

src/nvim/optionstr.c

@@ -1538,6 +1538,15 @@ const char *did_set_foldcolumn(optset_T *args)
   return NULL;
 }
 
+int expand_set_foldcolumn(optexpand_T *args, int *numMatches, char ***matches)
+{
+  return expand_set_opt_string(args,
+                               p_fdc_values,
+                               ARRAY_SIZE(p_fdc_values) - 1,
+                               numMatches,
+                               matches);
+}
+
 /// The 'foldexpr' option is changed.
 const char *did_set_foldexpr(optset_T *args)
 {
@@ -1691,6 +1700,15 @@ const char *did_set_inccommand(optset_T *args FUNC_ATTR_UNUSED)
   return did_set_opt_strings(p_icm, p_icm_values, false);
 }
 
+int expand_set_inccommand(optexpand_T *args, int *numMatches, char ***matches)
+{
+  return expand_set_opt_string(args,
+                               p_icm_values,
+                               ARRAY_SIZE(p_icm_values) - 1,
+                               numMatches,
+                               matches);
+}
+
 /// The 'isident' or the 'iskeyword' or the 'isprint' or the 'isfname' option is
 /// changed.
 const char *did_set_isopt(optset_T *args)
@@ -1943,6 +1961,16 @@ const char *did_set_mousescroll(optset_T *args FUNC_ATTR_UNUSED)
   return NULL;
 }
 
+int expand_set_mousescroll(optexpand_T *args, int *numMatches, char ***matches)
+{
+  static char *(p_mousescroll_values[]) = { "hor:", "ver:", NULL };
+  return expand_set_opt_string(args,
+                               p_mousescroll_values,
+                               ARRAY_SIZE(p_mousescroll_values) - 1,
+                               numMatches,
+                               matches);
+}
+
 /// The 'nrformats' option is changed.
 const char *did_set_nrformats(optset_T *args)
 {
@@ -2412,6 +2440,15 @@ const char *did_set_termpastefilter(optset_T *args FUNC_ATTR_UNUSED)
   return did_set_opt_flags(p_tpf, p_tpf_values, &tpf_flags, true);
 }
 
+int expand_set_termpastefilter(optexpand_T *args, int *numMatches, char ***matches)
+{
+  return expand_set_opt_string(args,
+                               p_tpf_values,
+                               ARRAY_SIZE(p_tpf_values) - 1,
+                               numMatches,
+                               matches);
+}
+
 /// The 'titlestring' or the 'iconstring' option is changed.
 static const char *did_set_titleiconstring(optset_T *args, int flagval)
 {
@@ -2625,7 +2662,8 @@ const char *did_set_winbar(optset_T *args)
   return did_set_statustabline_rulerformat(args, false, false);
 }
 
-const char *did_set_winhl(optset_T *args)
+/// The 'winhighlight' option is changed.
+const char *did_set_winhighlight(optset_T *args)
 {
   win_T *win = (win_T *)args->os_win;
   if (!parse_winhl_opt(win)) {
@@ -2634,6 +2672,11 @@ const char *did_set_winhl(optset_T *args)
   return NULL;
 }
 
+int expand_set_winhighlight(optexpand_T *args, int *numMatches, char ***matches)
+{
+  return expand_set_opt_generic(args, get_highlight_name, numMatches, matches);
+}
+
 // When 'syntax' is set, load the syntax of that name
 static void do_syntax_autocmd(buf_T *buf, bool value_changed)
 {

test/functional/editor/completion_spec.lua

@@ -941,6 +941,15 @@ describe('completion', function()
     end)
   end)
 
+  it('cmdline completion supports various string options', function()
+    eq('auto', funcs.getcompletion('set foldcolumn=', 'cmdline')[2])
+    eq({'nosplit', 'split'}, funcs.getcompletion('set inccommand=', 'cmdline'))
+    eq({'ver:3,hor:6', 'hor:', 'ver:'}, funcs.getcompletion('set mousescroll=', 'cmdline'))
+    eq('BS', funcs.getcompletion('set termpastefilter=', 'cmdline')[2])
+    eq('SpecialKey', funcs.getcompletion('set winhighlight=', 'cmdline')[1])
+    eq('SpecialKey', funcs.getcompletion('set winhighlight=NonText:', 'cmdline')[1])
+  end)
+
   describe('from the commandline window', function()
     it('is cleared after CTRL-C', function ()
       feed('q:')