patch 8.0.0255: setpos() does not use the buffer argument for all marks

Problem:    When calling setpos() with a buffer argument it often is ignored.
            (Matthew Malcomson)
Solution:   Make the buffer argument work for all marks local to a buffer.
            (neovim #5713)  Add more tests.

runtime/doc/eval.txt

@@ -6798,10 +6798,12 @@ setpos({expr}, {list})
 		    [bufnum, lnum, col, off, curswant]
 
 		"bufnum" is the buffer number.  Zero can be used for the
-		current buffer.  Setting the cursor is only possible for
-		the current buffer.  To set a mark in another buffer you can
-		use the |bufnr()| function to turn a file name into a buffer
-		number.
+		current buffer.  When setting an uppercase mark "bufnum" is
+		used for the mark position.  For other marks it specifies the
+		buffer to set the mark in.  You can use the |bufnr()| function
+		to turn a file name into a buffer number.
+		For setting the cursor and the ' mark "bufnum" is ignored,
+		since these are associated with a window, not a buffer.
 		Does not change the jumplist.
 
 		"lnum" and "col" are the position in the buffer.  The first

src/mark.c

@@ -57,6 +57,7 @@ setmark(int c)
 setmark_pos(int c, pos_T *pos, int fnum)
 {
     int		i;
+    buf_T	*buf;
 
     /* Check for a special key (may cause islower() to crash). */
     if (c < 0)
@@ -75,9 +76,13 @@ setmark_pos(int c, pos_T *pos, int fnum)
 	return OK;
     }
 
+    buf = buflist_findnr(fnum);
+    if (buf == NULL)
+	return FAIL;
+
     if (c == '"')
     {
-	curbuf->b_last_cursor = *pos;
+	buf->b_last_cursor = *pos;
 	return OK;
     }
 
@@ -85,31 +90,31 @@ setmark_pos(int c, pos_T *pos, int fnum)
      * file. */
     if (c == '[')
     {
-	curbuf->b_op_start = *pos;
+	buf->b_op_start = *pos;
 	return OK;
     }
     if (c == ']')
     {
-	curbuf->b_op_end = *pos;
+	buf->b_op_end = *pos;
 	return OK;
     }
 
     if (c == '<' || c == '>')
     {
 	if (c == '<')
-	    curbuf->b_visual.vi_start = *pos;
+	    buf->b_visual.vi_start = *pos;
 	else
-	    curbuf->b_visual.vi_end = *pos;
-	if (curbuf->b_visual.vi_mode == NUL)
+	    buf->b_visual.vi_end = *pos;
+	if (buf->b_visual.vi_mode == NUL)
 	    /* Visual_mode has not yet been set, use a sane default. */
-	    curbuf->b_visual.vi_mode = 'v';
+	    buf->b_visual.vi_mode = 'v';
 	return OK;
     }
 
     if (ASCII_ISLOWER(c))
     {
 	i = c - 'a';
-	curbuf->b_namedm[i] = *pos;
+	buf->b_namedm[i] = *pos;
 	return OK;
     }
     if (ASCII_ISUPPER(c) || VIM_ISDIGIT(c))
@@ -396,7 +401,8 @@ getmark_buf_fnum(
     {
 	startp = &buf->b_visual.vi_start;
 	endp = &buf->b_visual.vi_end;
-	if ((c == '<') == lt(*startp, *endp))
+	if (((c == '<') == lt(*startp, *endp) || endp->lnum == 0)
+							  && startp->lnum != 0)
 	    posp = startp;
 	else
 	    posp = endp;

src/testdir/test_marks.vim

@@ -24,3 +24,47 @@ function! Test_Incr_Marks()
   call assert_equal("XXX 123 123", getline(3))
   enew!
 endfunction
+
+func Test_setpos()
+  new one
+  let onebuf = bufnr('%')
+  let onewin = win_getid()
+  call setline(1, ['aaa', 'bbb', 'ccc'])
+  new two
+  let twobuf = bufnr('%')
+  let twowin = win_getid()
+  call setline(1, ['aaa', 'bbb', 'ccc'])
+
+  " for the cursor the buffer number is ignored
+  call setpos(".", [0, 2, 1, 0])
+  call assert_equal([0, 2, 1, 0], getpos("."))
+  call setpos(".", [onebuf, 3, 3, 0])
+  call assert_equal([0, 3, 3, 0], getpos("."))
+
+  call setpos("''", [0, 1, 3, 0])
+  call assert_equal([0, 1, 3, 0], getpos("''"))
+  call setpos("''", [onebuf, 2, 2, 0])
+  call assert_equal([0, 2, 2, 0], getpos("''"))
+
+  " buffer-local marks
+  for mark in ["'a", "'\"", "'[", "']", "'<", "'>"]
+    call win_gotoid(twowin)
+    call setpos(mark, [0, 2, 1, 0])
+    call assert_equal([0, 2, 1, 0], getpos(mark), "for mark " . mark)
+    call setpos(mark, [onebuf, 1, 3, 0])
+    call win_gotoid(onewin)
+    call assert_equal([0, 1, 3, 0], getpos(mark), "for mark " . mark)
+  endfor
+
+  " global marks
+  call win_gotoid(twowin)
+  call setpos("'N", [0, 2, 1, 0])
+  call assert_equal([twobuf, 2, 1, 0], getpos("'N"))
+  call setpos("'N", [onebuf, 1, 3, 0])
+  call assert_equal([onebuf, 1, 3, 0], getpos("'N"))
+
+  call win_gotoid(onewin)
+  bwipe!
+  call win_gotoid(twowin)
+  bwipe!
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    255,
 /**/
     254,
 /**/