vim-patch:8.0.1274: setbufline() fails when using folding

Problem:    setbufline() fails when using folding.
Solution:   Set "curwin" if needed. (Ozaki Kiichi, closes vim/vim#2293)
0c4dc88a63

src/nvim/eval.c

@@ -14851,7 +14851,8 @@ static void set_buffer_lines(buf_T *buf, linenr_T lnum, typval_T *lines,
   listitem_T  *li = NULL;
   long        added = 0;
   linenr_T    lcount;
-  buf_T       *curbuf_save;
+  buf_T       *curbuf_save = NULL;
+  win_T       *curwin_save = NULL;
   int         is_curbuf = buf == curbuf;
 
   // When using the current buffer ml_mfp will be set if needed.  Useful when
@@ -14862,8 +14863,19 @@ static void set_buffer_lines(buf_T *buf, linenr_T lnum, typval_T *lines,
     return;
   }
 
-  curbuf_save = curbuf;
+  if (!is_curbuf) {
-  curbuf = buf;
+    wininfo_T *wip;
+
+    curbuf_save = curbuf;
+    curwin_save = curwin;
+    curbuf = buf;
+    for (wip = buf->b_wininfo; wip != NULL; wip = wip->wi_next) {
+      if (wip->wi_win != NULL) {
+        curwin = wip->wi_win;
+        break;
+      }
+    }
+  }
 
   lcount = curbuf->b_ml.ml_line_count;
 
@@ -14926,7 +14938,10 @@ static void set_buffer_lines(buf_T *buf, linenr_T lnum, typval_T *lines,
     appended_lines_mark(lcount, added);
   }
 
-  curbuf = curbuf_save;
+  if (!is_curbuf) {
+     curbuf = curbuf_save;
+     curwin = curwin_save;
+  }
 }
 
 /// "setbufline()" function

src/nvim/testdir/test_bufline.vim

@@ -27,6 +27,32 @@ func Test_setbufline_getbufline()
   exe "bwipe! " . b
 endfunc
 
+func Test_setbufline_getbufline_fold()
+  split Xtest
+  setlocal foldmethod=expr foldexpr=0
+  let b = bufnr('%')
+  new
+  call assert_equal(0, setbufline(b, 1, ['foo', 'bar']))
+  call assert_equal(['foo'], getbufline(b, 1))
+  call assert_equal(['bar'], getbufline(b, 2))
+  call assert_equal(['foo', 'bar'], getbufline(b, 1, 2))
+  exe "bwipe!" b
+  bwipe!
+endfunc
+
+func Test_setbufline_getbufline_fold_tab()
+  split Xtest
+  setlocal foldmethod=expr foldexpr=0
+  let b = bufnr('%')
+  tab new
+  call assert_equal(0, setbufline(b, 1, ['foo', 'bar']))
+  call assert_equal(['foo'], getbufline(b, 1))
+  call assert_equal(['bar'], getbufline(b, 2))
+  call assert_equal(['foo', 'bar'], getbufline(b, 1, 2))
+  exe "bwipe!" b
+  bwipe!
+endfunc
+
 func Test_setline_startup()
   let cmd = GetVimCommand('Xscript')
   if cmd == ''