patch 9.1.1742: complete: preinsert does not work well with preinsert

Problem:  complete: preinsert does not work well with preinsert
Solution: Make "preinsert" completeopt value work with autocompletion
          (Girish Palya)

This change extends Insert mode autocompletion so that 'preinsert' also
works when 'autocomplete' is enabled.

Try: `:set ac cot=preinsert`

See `:help 'cot'` for more details.

closes: #18213

Signed-off-by: Girish Palya <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: girishji

runtime/doc/insert.txt

@@ -1,4 +1,4 @@
-*insert.txt*    For Vim version 9.1.  Last change: 2025 Aug 25
+*insert.txt*    For Vim version 9.1.  Last change: 2025 Sep 08
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1150,7 +1150,26 @@ any of them at any time by typing |CTRL-X|, which temporarily suspends
 autocompletion.  To use |i_CTRL-N| or |i_CTRL-X_CTRL-N| specifically, press
 |CTRL-E| first to dismiss the popup menu (see |complete_CTRL-E|).
 
-See also 'autocomplete', 'autocompletetimeout' and 'autocompletedelay'.
+						*ins-autocompletion-example*
+Example setup~
+A typical configuration for automatic completion with a popup menu: >
+	set autocomplete
+	set complete=.^5,w^5,b^5,u^5
+	set completeopt=popup
+
+	inoremap <silent><expr> <Tab>   pumvisible() ? "\<C-n>" : "\<Tab>"
+	inoremap <silent><expr> <S-Tab> pumvisible() ? "\<C-p>" : "\<S-Tab>"
+<
+This enables automatic completion with suggestions from the current buffer,
+other windows, and listed buffers, displayed in a popup menu.  Each source is
+limited to 5 candidates.  <Tab> and <S-Tab> move through the items when the
+menu is visible.  Optionally, add "preinsert" to 'completeopt' to insert the
+longest common prefix automatically.  You can also add other completion
+sources to 'complete' as needed.
+
+See also 'autocomplete', 'autocompletedelay' and 'autocompletetimeout'.
+
+For command-line autocompletion, see |cmdline-autocompletion|.
 
 
 FUNCTIONS FOR FINDING COMPLETIONS			*complete-functions*

runtime/doc/options.txt

@@ -1,4 +1,4 @@
-*options.txt*	For Vim version 9.1.  Last change: 2025 Sep 02
+*options.txt*	For Vim version 9.1.  Last change: 2025 Sep 08
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2124,10 +2124,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 						*'complete'* *'cpt'* *E535*
 'complete' 'cpt'	string	(default: ".,w,b,u,t,i")
 			local to buffer
-	This option specifies how keyword completion |ins-completion| works
-	when CTRL-P or CTRL-N are used.  It is also used for whole-line
-	completion |i_CTRL-X_CTRL-L|.  It indicates the type of completion
-	and the places to scan.  It is a comma-separated list of flags:
+	This option controls how completion |ins-completion| behaves when
+	using CTRL-P, CTRL-N, or |ins-autocompletion|.  It is also used for
+	whole-line completion |i_CTRL-X_CTRL-L|.  It indicates the type of
+	completion and the places to scan.  It is a comma-separated list of
+	flags:
 	.	scan the current buffer ('wrapscan' is ignored)
 	w	scan buffers from other windows
 	b	scan other loaded buffers that are in the buffer list
@@ -2179,9 +2180,11 @@ A jump table for the options with a short description can be found at |Q_op|.
 	   5. tags
 	   6. included files
 
-	As you can see, CTRL-N and CTRL-P can be used to do any 'iskeyword'-
-	based expansion (e.g., dictionary |i_CTRL-X_CTRL-K|, included patterns
-	|i_CTRL-X_CTRL-I|, tags |i_CTRL-X_CTRL-]| and normal expansions).
+	CTRL-N, CTRL-P, and |ins-autocompletion| can be used for any
+	'iskeyword'-based completion (dictionary |i_CTRL-X_CTRL-K|, included
+	patterns |i_CTRL-X_CTRL-I|, tags |i_CTRL-X_CTRL-]|, and normal
+	expansions).  With the "F" and "o" flags in 'complete', non-keywords
+	can also be completed.
 
 	An optional match limit can be specified for a completion source by
 	appending a caret ("^") followed by a {count} to the source flag.
@@ -2298,17 +2301,22 @@ A jump table for the options with a short description can be found at |Q_op|.
 		    {only works when compiled with the |+textprop| feature}
 
 	   preinsert
-		    Preinsert the portion of the first candidate word that is
-		    not part of the current completion leader and using the
-		    |hl-ComplMatchIns| highlight group.  In order for it to
-		    work, "fuzzy" must not be set and "menuone" must be set.
+		    When autocompletion is not enabled, inserts the part of the
+		    first candidate word beyond the current completion leader,
+		    highlighted with |hl-ComplMatchIns|.  The cursor does not
+		    move.  Requires 'fuzzy' unset and 'menuone' in 'completeopt'.
+
+		    When 'autocomplete' is enabled, inserts the longest common
+		    prefix of matches (from all shown items or buffer-specific
+		    matches), highlighted with |hl-PreInsert|.  This occurs only
+		    when no menu item is selected.  Press CTRL-Y to accept.
 
 	   preview  Show extra information about the currently selected
 		    completion in the preview window.  Only works in
 		    combination with "menu" or "menuone".
 
-	Only "fuzzy", "popup", "popuphidden" and "preview" have an effect when
-	'autocomplete' is enabled.
+	Only "fuzzy", "popup", "popuphidden", "preinsert" and "preview" have
+	an effect when 'autocomplete' is enabled.
 
 	This option does not apply to |cmdline-completion|. See 'wildoptions'
 	for that.
@@ -4654,7 +4662,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 				     #:TabLineSel,_:TabLineFill,!:CursorColumn,
 				     .:CursorLine,o:ColorColumn,q:QuickFixLine,
 				     z:StatusLineTerm,Z:StatusLineTermNC,
-				     g:MsgArea,h:ComplMatchIns")
+				     g:MsgArea,h:ComplMatchIns,I:PreInsert")
 			global
 	This option can be used to set highlighting mode for various
 	occasions.  It is a comma-separated list of character pairs.  The
@@ -4717,6 +4725,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	|hl-PmenuThumb|	 X  popup menu scrollbar thumb
 	|hl-PmenuMatch|	 k  popup menu matched text
 	|hl-PmenuMatchSel| <  popup menu matched text in selected line
+	|hl-PreInsert|	 I  text inserted when "preinsert" and 'autocomplete'
 
 	The display modes are:
 		r	reverse		(termcap entry "mr" and "me")

runtime/doc/syntax.txt

@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2025 Aug 18
+*syntax.txt*	For Vim version 9.1.  Last change: 2025 Sep 08
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -5998,6 +5998,8 @@ PmenuMatchSel	Popup menu: Matched text in selected item. Applied in
 		combination with |hl-PmenuSel|.
 							*hl-ComplMatchIns*
 ComplMatchIns	Matched text of the currently inserted completion.
+							*hl-PreInsert*
+PreInsert	Text inserted during autocompletion when "preinsert".
 							*hl-PopupSelected*
 PopupSelected	Popup window created with |popup_menu()|.  Linked to
 		|hl-PmenuSel| by default.

runtime/doc/tags

@@ -8366,6 +8366,7 @@ hl-PmenuSel	syntax.txt	/*hl-PmenuSel*
 hl-PmenuThumb	syntax.txt	/*hl-PmenuThumb*
 hl-PopupNotification	syntax.txt	/*hl-PopupNotification*
 hl-PopupSelected	syntax.txt	/*hl-PopupSelected*
+hl-PreInsert	syntax.txt	/*hl-PreInsert*
 hl-Question	syntax.txt	/*hl-Question*
 hl-QuickFixLine	syntax.txt	/*hl-QuickFixLine*
 hl-Scrollbar	syntax.txt	/*hl-Scrollbar*
@@ -8627,6 +8628,7 @@ inputrestore()	builtin.txt	/*inputrestore()*
 inputsave()	builtin.txt	/*inputsave()*
 inputsecret()	builtin.txt	/*inputsecret()*
 ins-autocompletion	insert.txt	/*ins-autocompletion*
+ins-autocompletion-example	insert.txt	/*ins-autocompletion-example*
 ins-completion	insert.txt	/*ins-completion*
 ins-completion-menu	insert.txt	/*ins-completion-menu*
 ins-expandtab	insert.txt	/*ins-expandtab*

runtime/syntax/vim.vim

@@ -2,7 +2,7 @@
 " Language:	   Vim script
 " Maintainer:	   Hirohito Higashi <h.east.727 ATMARK gmail.com>
 "	   Doug Kearns <[email protected]>
-" Last Change:	   2025 Aug 29
+" Last Change:	   2025 Sep 08
 " Former Maintainer: Charles E. Campbell
 
 " DO NOT CHANGE DIRECTLY.
@@ -145,8 +145,8 @@ syn keyword vimGroup contained Added Bold BoldItalic Boolean Changed Character C
 
 " Default highlighting groups {{{2
 " GEN_SYN_VIM: vimHLGroup, START_STR='syn keyword vimHLGroup contained', END_STR=''
-syn keyword vimHLGroup contained ErrorMsg IncSearch ModeMsg NonText StatusLine StatusLineNC EndOfBuffer VertSplit VisualNOS DiffText DiffTextAdd PmenuSbar TabLineSel TabLineFill TabPanel TabPanelSel TabPanelFill Cursor lCursor QuickFixLine CursorLineSign CursorLineFold CurSearch PmenuKind PmenuKindSel PmenuMatch PmenuMatchSel PmenuExtra PmenuExtraSel PopupSelected MessageWindow PopupNotification Normal Directory LineNr CursorLineNr MoreMsg Question Search SpellBad SpellCap SpellRare SpellLocal PmenuThumb Pmenu PmenuSel SpecialKey Title WarningMsg WildMenu Folded FoldColumn SignColumn Visual DiffAdd DiffChange DiffDelete TabLine CursorColumn CursorLine ColorColumn MatchParen StatusLineTerm StatusLineTermNC ToolbarLine ToolbarButton Menu Tooltip Scrollbar CursorIM
-syn keyword vimHLGroup contained ComplMatchIns LineNrAbove LineNrBelow MsgArea Terminal User1 User2 User3 User4 User5 User6 User7 User8 User9
+syn keyword vimHLGroup contained ErrorMsg IncSearch ModeMsg NonText StatusLine StatusLineNC EndOfBuffer VertSplit VisualNOS DiffText DiffTextAdd PmenuSbar TabLineSel TabLineFill TabPanel TabPanelSel TabPanelFill Cursor lCursor QuickFixLine CursorLineSign CursorLineFold CurSearch PmenuKind PmenuKindSel PmenuMatch PmenuMatchSel PmenuExtra PmenuExtraSel PopupSelected MessageWindow PopupNotification PreInsert Normal Directory LineNr CursorLineNr MoreMsg Question Search SpellBad SpellCap SpellRare SpellLocal PmenuThumb Pmenu PmenuSel SpecialKey Title WarningMsg WildMenu Folded FoldColumn SignColumn Visual DiffAdd DiffChange DiffDelete TabLine CursorColumn CursorLine ColorColumn MatchParen StatusLineTerm StatusLineTermNC ToolbarLine ToolbarButton Menu Tooltip Scrollbar
+syn keyword vimHLGroup contained CursorIM ComplMatchIns LineNrAbove LineNrBelow MsgArea Terminal User1 User2 User3 User4 User5 User6 User7 User8 User9
 syn match vimHLGroup contained "\<Conceal\>"
 syn case match
 

src/edit.c

@@ -693,7 +693,11 @@ edit(
 			&& stop_arrow() == OK)
 		{
 		    ins_compl_delete();
-		    ins_compl_insert(FALSE);
+		    if (ins_compl_has_preinsert()
+			    && ins_compl_has_autocomplete())
+			(void)ins_compl_insert(FALSE, TRUE);
+		    else
+			(void)ins_compl_insert(FALSE, FALSE);
 		}
 		// Delete preinserted text when typing special chars
 		else if (IS_WHITE_NL_OR_NUL(c) && ins_compl_preinsert_effect())

src/highlight.c

@@ -269,6 +269,7 @@ static char *(highlight_init_both[]) = {
     "default link PopupSelected PmenuSel",
     "default link MessageWindow WarningMsg",
     "default link PopupNotification WarningMsg",
+    "default link PreInsert Added",
     CENT("Normal cterm=NONE", "Normal gui=NONE"),
     NULL
 };