To: vim_dev@googlegroups.com
Subject: Patch 8.2.1821
Fcc: outbox
From: Bram Moolenaar <Bram@moolenaar.net>
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------------

Patch 8.2.1821
Problem:    Vim9: concatenating to a NULL list doesn't work.
Solution:   Handle a NULL list like an empty list. (closes #7064)
Files:      src/list.c, src/testdir/test_vim9_assign.vim


*** ../vim-8.2.1820/src/list.c	2020-09-16 23:23:33.026882158 +0200
--- src/list.c	2020-10-10 15:35:05.046678599 +0200
***************
*** 824,830 ****
  }
  
  /*
!  * Extend "l1" with "l2".
   * If "bef" is NULL append at the end, otherwise insert before this item.
   * Returns FAIL when out of memory.
   */
--- 824,830 ----
  }
  
  /*
!  * Extend "l1" with "l2".  "l1" must not be NULL.
   * If "bef" is NULL append at the end, otherwise insert before this item.
   * Returns FAIL when out of memory.
   */
***************
*** 832,839 ****
  list_extend(list_T *l1, list_T *l2, listitem_T *bef)
  {
      listitem_T	*item;
!     int		todo = l2->lv_len;
  
      CHECK_LIST_MATERIALIZE(l1);
      CHECK_LIST_MATERIALIZE(l2);
  
--- 832,844 ----
  list_extend(list_T *l1, list_T *l2, listitem_T *bef)
  {
      listitem_T	*item;
!     int		todo;
  
+     // NULL list is equivalent to an empty list: nothing to do.
+     if (l2 == NULL || l2->lv_len == 0)
+ 	return OK;
+ 
+     todo = l2->lv_len;
      CHECK_LIST_MATERIALIZE(l1);
      CHECK_LIST_MATERIALIZE(l2);
  
***************
*** 854,868 ****
  {
      list_T	*l;
  
-     if (l1 == NULL || l2 == NULL)
- 	return FAIL;
- 
      // make a copy of the first list.
!     l = list_copy(l1, FALSE, 0);
      if (l == NULL)
  	return FAIL;
      tv->v_type = VAR_LIST;
      tv->vval.v_list = l;
  
      // append all items from the second list
      return list_extend(l, l2, NULL);
--- 859,875 ----
  {
      list_T	*l;
  
      // make a copy of the first list.
!     if (l1 == NULL)
! 	l = list_alloc();
!     else
! 	l = list_copy(l1, FALSE, 0);
      if (l == NULL)
  	return FAIL;
      tv->v_type = VAR_LIST;
      tv->vval.v_list = l;
+     if (l1 == NULL)
+ 	++l->lv_refcount;
  
      // append all items from the second list
      return list_extend(l, l2, NULL);
*** ../vim-8.2.1820/src/testdir/test_vim9_assign.vim	2020-10-03 22:51:42.894813399 +0200
--- src/testdir/test_vim9_assign.vim	2020-10-10 15:31:39.415142100 +0200
***************
*** 236,241 ****
--- 236,253 ----
        assert_equal(#{one: 1}, d)
    END
    CheckScriptSuccess(lines)
+ 
+   # appending to NULL list from a function
+   lines =<< trim END
+       vim9script
+       var list: list<string>
+       def Func()
+         list += ['a', 'b']
+       enddef
+       Func()
+       assert_equal(['a', 'b'], list)
+   END
+   CheckScriptSuccess(lines)
  enddef
  
  def Test_single_letter_vars()
*** ../vim-8.2.1820/src/version.c	2020-10-10 15:05:19.970305397 +0200
--- src/version.c	2020-10-10 15:22:25.148112016 +0200
***************
*** 752,753 ****
--- 752,755 ----
  {   /* Add new patch number below this line */
+ /**/
+     1821,
  /**/

-- 
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 /// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net   \\\
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