vim-patch:9.0.0590: after exiting Insert mode spelling not checked in next line

Problem:    After exiting Insert mode spelling is not checked in the next
            line.
Solution:   When spelling is enabled redraw the next line after exiting Insert
            mode in case the spell highlight needs updating.

https://github.com/vim/vim/commit/ee09fcc9b6cf24e02899461809da9a5148208ea5

Co-authored-by: Bram Moolenaar <Bram@vim.org>

3 files changed, 21 insertions, 9 deletions

diff --git a/src/nvim/drawline.c b/src/nvim/drawline.c
index a49b2ac6d6..54da38a6ff 100644
--- a/src/nvim/drawline.c
+++ b/src/nvim/drawline.c
@@ -1203,12 +1203,7 @@ int win_line(win_T *wp, linenr_T lnum, int startrow, int endrow, bool nochange,
       draw_color_col = advance_color_col(VCOL_HLC, &color_cols);
     }
 
-    if (wp->w_p_spell
-        && !has_fold
-        && !end_fill
-        && *wp->w_s->b_p_spl != NUL
-        && !GA_EMPTY(&wp->w_s->b_langp)
-        && *(char **)(wp->w_s->b_langp.ga_data) != NULL) {
+    if (!has_fold && !end_fill && spell_check_window(wp)) {
       // Prepare for spell checking.
       has_spell = true;
       extra_check = true;
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index a25387f5a6..612a1a1bda 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -53,6 +53,7 @@
 #include "nvim/popupmenu.h"
 #include "nvim/pos.h"
 #include "nvim/search.h"
+#include "nvim/spell.h"
 #include "nvim/state.h"
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
@@ -3394,6 +3395,14 @@ static bool ins_esc(long *count, int cmdchar, bool nomove)
 
   check_spell_redraw();
 
+  // When text has been changed in this line, possibly the start of the next
+  // line may have SpellCap that should be removed or it needs to be
+  // displayed.  Schedule the next line for redrawing just in case.
+  if (spell_check_window(curwin)
+      && curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count) {
+    redrawWinline(curwin, curwin->w_cursor.lnum + 1);
+  }
+
   int temp = curwin->w_cursor.col;
   if (disabled_redraw) {
     RedrawingDisabled--;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 84875261f1..498bd56b9e 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -1189,11 +1189,19 @@ bool spell_valid_case(int wordflags, int treeflags)
                  || (wordflags & WF_ONECAP) != 0));
 }
 
-// Returns true if spell checking is not enabled.
+/// Return true if spell checking is enabled for "wp".
+bool spell_check_window(win_T *wp)
+{
+  return wp->w_p_spell
+         && *wp->w_s->b_p_spl != NUL
+         && wp->w_s->b_langp.ga_len > 0
+         && *(char **)(wp->w_s->b_langp.ga_data) != NULL;
+}
+
+/// Return true and give an error if spell checking is not enabled.
 bool no_spell_checking(win_T *wp)
 {
-  if (!wp->w_p_spell || *wp->w_s->b_p_spl == NUL
-      || GA_EMPTY(&wp->w_s->b_langp)) {
+  if (!wp->w_p_spell || *wp->w_s->b_p_spl == NUL || GA_EMPTY(&wp->w_s->b_langp)) {
     emsg(_(e_no_spell));
     return true;
   }