vim-patch:9.1.1742: complete: preinsert does not work well with 'autocomplete' (#35692)

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: vim/vim#18213

https://github.com/vim/vim/commit/fa6fd41a943e6442c1a2ce6b0a237298b00ecca0

Co-authored-by: Girish Palya <girishji@gmail.com>

1 files changed, 21 insertions, 13 deletions

diff --git a/runtime/lua/vim/_meta/options.lua b/runtime/lua/vim/_meta/options.lua
index d517d6dca0..a545b75c26 100644
--- a/runtime/lua/vim/_meta/options.lua
+++ b/runtime/lua/vim/_meta/options.lua
@@ -1044,10 +1044,11 @@ vim.o.cms = vim.o.commentstring
 vim.bo.commentstring = vim.o.commentstring
 vim.bo.cms = vim.bo.commentstring
 
---- 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
@@ -1095,9 +1096,11 @@ vim.bo.cms = vim.bo.commentstring
 --- (gzipped files for example).  Unloaded buffers are not scanned for
 --- whole-line completion.
 ---
---- 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.
@@ -1215,17 +1218,22 @@ vim.go.cia = vim.go.completeitemalign
 --- 	    with "menu" or "menuone".  Overrides "preview".
 ---
 ---    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" and "preview" have an effect when 'autocomplete'
---- is enabled.
+--- Only "fuzzy", "popup", "preinsert" and "preview" have an effect when
+--- 'autocomplete' is enabled.
 ---
 --- This option does not apply to `cmdline-completion`. See 'wildoptions'
 --- for that.