patch 9.1.0418: Cannot move to previous/next rare word

Problem:  Cannot move to previous/next rare word
          (Colin Kennedy)
Solution: Add the ]r and [r motions (Christ van Willegen)

fixes: #14773
closes: #14780

Signed-off-by: Christ van Willegen - van Noort <github.com@vanwillegen-vannoort.nl>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/spell.txt b/runtime/doc/spell.txt
index ab3b120..809e3a8 100644
--- a/runtime/doc/spell.txt
+++ b/runtime/doc/spell.txt
@@ -1,4 +1,4 @@
-*spell.txt*	For Vim version 9.1.  Last change: 2024 May 11
+*spell.txt*	For Vim version 9.1.  Last change: 2024 May 17
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -62,6 +62,17 @@
 							*[S*
 [S			Like "]S" but search backwards.
 
+							*]r*
+]r			Move to next "rare" word after the cursor.
+			A count before the command can be used to repeat.
+			'wrapscan' applies.
+
+							*[r*
+[r			Like "]r" but search backwards, find the "rare"
+			word before the cursor.  Doesn't recognize words
+			split over two lines, thus may stop at words that are
+			not highlighted as rare.
+
 
 To add words to your own word list:
 
diff --git a/runtime/doc/tags b/runtime/doc/tags
index d354df1..2c3fd7f 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -5876,6 +5876,7 @@
 [p	change.txt	/*[p*
 [pattern]	pattern.txt	/*[pattern]*
 [quotex]	intro.txt	/*[quotex]*
+[r	spell.txt	/*[r*
 [range]	cmdline.txt	/*[range]*
 [s	spell.txt	/*[s*
 [star	motion.txt	/*[star*
@@ -5904,6 +5905,7 @@
 ]i	tagsrch.txt	/*]i*
 ]m	motion.txt	/*]m*
 ]p	change.txt	/*]p*
+]r	spell.txt	/*]r*
 ]s	spell.txt	/*]s*
 ]star	motion.txt	/*]star*
 ]z	fold.txt	/*]z*
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index 192c3ee..1c5a29f 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2024 May 05
+*version9.txt*  For Vim version 9.1.  Last change: 2024 May 17
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41587,15 +41587,17 @@
 
 Highlighting: ~
 
-|hl-MsgArea|		highlighting of the Command-line and messages area.
+|hl-MsgArea|		highlighting of the Command-line and messages area
 
 Commands: ~
 
+|[r| and |]r|		to move the cursor to previous/next rare word
+
 
 Options: ~
 
 'winfixbuf'		Keep buffer focused in a window
-'t_xo'			Terminal uses XON/XOFF handshaking (e.g. vt420).
+'t_xo'			Terminal uses XON/XOFF handshaking (e.g. vt420)
 
 ==============================================================================
 INCOMPATIBLE CHANGES				*incompatible-9.2*
diff --git a/src/drawline.c b/src/drawline.c
index 81577be..9502fc5 100644
--- a/src/drawline.c
+++ b/src/drawline.c
@@ -1801,7 +1801,7 @@
 	    pos = wp->w_cursor;
 	    wp->w_cursor.lnum = lnum;
 	    wp->w_cursor.col = linecol;
-	    len = spell_move_to(wp, FORWARD, TRUE, TRUE, &spell_hlf);
+	    len = spell_move_to(wp, FORWARD, SMT_ALL, TRUE, &spell_hlf);
 
 	    // spell_move_to() may call ml_get() and make "line" invalid
 	    line = ml_get_buf(wp->w_buffer, lnum, FALSE);
diff --git a/src/evalfunc.c b/src/evalfunc.c
index fecdc43..cd3a6fd 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -10959,7 +10959,7 @@
     if (argvars[0].v_type == VAR_UNKNOWN)
     {
 	// Find the start and length of the badly spelled word.
-	len = spell_move_to(curwin, FORWARD, TRUE, TRUE, &attr);
+	len = spell_move_to(curwin, FORWARD, SMT_ALL, TRUE, &attr);
 	if (len != 0)
 	{
 	    word = ml_get_cursor();
diff --git a/src/insexpand.c b/src/insexpand.c
index 93a56a8..1520d57 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -5195,7 +5195,7 @@
 {
     pos_T	tpos = curwin->w_cursor;
 
-    spell_bad_len = spell_move_to(curwin, BACKWARD, TRUE, TRUE, NULL);
+    spell_bad_len = spell_move_to(curwin, BACKWARD, SMT_ALL, TRUE, NULL);
     if (curwin->w_cursor.col != tpos.col)
 	start_arrow(&tpos);
 }
diff --git a/src/normal.c b/src/normal.c
index fef2826..580eb72 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -2593,7 +2593,7 @@
 	// off this fails and find_ident_under_cursor() is
 	// used below.
 	emsg_off++;
-	len = spell_move_to(curwin, FORWARD, TRUE, TRUE, NULL);
+	len = spell_move_to(curwin, FORWARD, SMT_ALL, TRUE, NULL);
 	emsg_off--;
 	if (len != 0 && curwin->w_cursor.col <= pos.col)
 	    ptr = ml_get_pos(&curwin->w_cursor);
@@ -4529,13 +4529,15 @@
 #endif
 
 #ifdef FEAT_SPELL
-    // "[s", "[S", "]s" and "]S": move to next spell error.
-    else if (cap->nchar == 's' || cap->nchar == 'S')
+    // "[r", "[s", "[S", "]r", "]s" and "]S": move to next spell error.
+    else if (cap->nchar == 'r' || cap->nchar == 's' || cap->nchar == 'S')
     {
 	setpcmark();
 	for (n = 0; n < cap->count1; ++n)
 	    if (spell_move_to(curwin, cap->cmdchar == ']' ? FORWARD : BACKWARD,
-			  cap->nchar == 's' ? TRUE : FALSE, FALSE, NULL) == 0)
+			  cap->nchar == 's' ? SMT_ALL :
+			  cap->nchar == 'r' ? SMT_RARE :
+			  SMT_BAD, FALSE, NULL) == 0)
 	    {
 		clearopbeep(cap->oap);
 		break;
diff --git a/src/proto/spell.pro b/src/proto/spell.pro
index 98a1353..680bf34 100644
--- a/src/proto/spell.pro
+++ b/src/proto/spell.pro
@@ -6,7 +6,7 @@
 int valid_word_prefix(int totprefcnt, int arridx, int flags, char_u *word, slang_T *slang, int cond_req);
 int spell_valid_case(int wordflags, int treeflags);
 int spell_check_window(win_T *wp);
-int spell_move_to(win_T *wp, int dir, int allwords, int curline, hlf_T *attrp);
+int spell_move_to(win_T *wp, int dir, smt_T behaviour, int curline, hlf_T *attrp);
 void spell_cat_line(char_u *buf, char_u *line, int maxlen);
 char_u *spell_enc(void);
 slang_T *slang_alloc(char_u *lang);
diff --git a/src/spell.c b/src/spell.c
index 43c521d..3ae484c 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -1336,7 +1336,7 @@
 spell_move_to(
     win_T	*wp,
     int		dir,		// FORWARD or BACKWARD
-    int		allwords,	// TRUE for "[s"/"]s", FALSE for "[S"/"]S"
+    smt_T	behaviour,	// Behaviour of the function
     int		curline,
     hlf_T	*attrp)		// return: attributes of bad word or NULL
 				// (only when "dir" is FORWARD)
@@ -1441,7 +1441,9 @@
 	    if (attr != HLF_COUNT)
 	    {
 		// We found a bad word.  Check the attribute.
-		if (allwords || attr == HLF_SPB)
+		if (behaviour == SMT_ALL
+				|| (behaviour == SMT_BAD && attr == HLF_SPB)
+				|| (behaviour == SMT_RARE && attr == HLF_SPR))
 		{
 		    // When searching forward only accept a bad word after
 		    // the cursor.
diff --git a/src/spellsuggest.c b/src/spellsuggest.c
index c6e6183..b305bfb 100644
--- a/src/spellsuggest.c
+++ b/src/spellsuggest.c
@@ -512,7 +512,7 @@
 	    badlen = ml_get_curline_len() - (int)curwin->w_cursor.col;
     }
     // Find the start of the badly spelled word.
-    else if (spell_move_to(curwin, FORWARD, TRUE, TRUE, NULL) == 0
+    else if (spell_move_to(curwin, FORWARD, SMT_ALL, TRUE, NULL) == 0
 	    || curwin->w_cursor.col > prev_cursor.col)
     {
 	// No bad word or it starts after the cursor: use the word under the
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index b41f5f4..a80b130 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -278,6 +278,7 @@
 	test_spell \
 	test_spell_utf8 \
 	test_spellfile \
+	test_spellrare \
 	test_startup \
 	test_startup_utf8 \
 	test_stat \
@@ -521,6 +522,7 @@
 	test_spell.res \
 	test_spell_utf8.res \
 	test_spellfile.res \
+	test_spellrare.res \
 	test_startup.res \
 	test_stat.res \
 	test_statusline.res \
diff --git a/src/testdir/test_spellrare.vim b/src/testdir/test_spellrare.vim
new file mode 100644
index 0000000..bbb13c2
--- /dev/null
+++ b/src/testdir/test_spellrare.vim
@@ -0,0 +1,61 @@
+" Test spell checking
+
+source check.vim
+CheckFeature spell
+
+" Test spellbadword() with argument, specifically to move to "rare" words
+" in normal mode.
+func Test_spellrareword()
+  set spell
+
+  " Create a small word list to test that spellbadword('...')
+  " can return ['...', 'rare'].
+  let lines =<< trim END
+     foo
+     foobar/?
+     foobara/?
+END
+   call writefile(lines, 'Xwords', 'D')
+
+   mkspell! Xwords.spl Xwords
+   set spelllang=Xwords.spl
+   call assert_equal(['foobar', 'rare'], spellbadword('foo foobar'))
+
+  new
+  call setline(1, ['foo', '', 'foo bar foo bar foobara foo foo foo foobar', '', 'End'])
+  set spell wrapscan
+  normal ]s
+  call assert_equal('foo', expand('<cword>'))
+  normal ]s
+  call assert_equal('bar', expand('<cword>'))
+
+  normal ]r
+  call assert_equal('foobara', expand('<cword>'))
+  normal ]r
+  call assert_equal('foobar', expand('<cword>'))
+  normal ]r
+  call assert_equal('foobara', expand('<cword>'))
+  normal 2]r
+  call assert_equal('foobara', expand('<cword>'))
+ 
+  normal [r
+  call assert_equal('foobar', expand('<cword>'))
+  normal [r
+  call assert_equal('foobara', expand('<cword>'))
+  normal [r
+  call assert_equal('foobar', expand('<cword>'))
+  normal 2[r
+  call assert_equal('foobar', expand('<cword>'))
+
+  bwipe!
+  set nospell
+
+  call delete('Xwords.spl')
+  set spelllang&
+  set spell&
+
+  " set 'encoding' to clear the word list
+  set encoding=utf-8
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 682a468..ad3b585 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    418,
+/**/
     417,
 /**/
     416,
diff --git a/src/vim.h b/src/vim.h
index f359245..654e523 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1530,6 +1530,15 @@
 		  'z', 'Z', 'g'}
 
 /*
+ * Values for behaviour in spell_move_to
+ */
+typedef enum
+{
+    SMT_ALL = 0		    // Move to "all" words
+    , SMT_BAD		    // Move to "bad" words only
+    , SMT_RARE		    // Move to "rare" words only
+} smt_T;
+/*
  * Boolean constants
  */
 #ifndef TRUE