vim-patch:8.2.0175: crash when removing list element in map()

Problem:    Crash when removing list element in map().
Solution:   Lock the list. (closes vim/vim#2652)
https://github.com/vim/vim/commit/db661fb95dc41b7a9438cf3cd4e77f8410bc81c0

2 files changed, 20 insertions, 0 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 6dbdc09c3b..d25903c12a 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6468,6 +6468,10 @@ void filter_map(typval_T *argvars, typval_T *rettv, int map)
     if (argvars[0].v_type == VAR_DICT) {
       vimvars[VV_KEY].vv_type = VAR_STRING;
 
+      const VarLockStatus prev_lock = d->dv_lock;
+      if (map && d->dv_lock == VAR_UNLOCKED) {
+        d->dv_lock = VAR_LOCKED;
+      }
       ht = &d->dv_hashtab;
       hash_lock(ht);
       todo = (int)ht->ht_used;
@@ -6498,6 +6502,7 @@ void filter_map(typval_T *argvars, typval_T *rettv, int map)
         }
       }
       hash_unlock(ht);
+      d->dv_lock = prev_lock;
     } else if (argvars[0].v_type == VAR_BLOB) {
       vimvars[VV_KEY].vv_type = VAR_NUMBER;
 
@@ -6530,6 +6535,10 @@ void filter_map(typval_T *argvars, typval_T *rettv, int map)
       assert(argvars[0].v_type == VAR_LIST);
       vimvars[VV_KEY].vv_type = VAR_NUMBER;
 
+      const VarLockStatus prev_lock = tv_list_locked(l);
+      if (map && tv_list_locked(l) == VAR_UNLOCKED) {
+        tv_list_set_lock(l, VAR_LOCKED);
+      }
       for (listitem_T *li = tv_list_first(l); li != NULL;) {
         if (map
             && var_check_lock(TV_LIST_ITEM_TV(li)->v_lock, arg_errmsg,
@@ -6548,6 +6557,7 @@ void filter_map(typval_T *argvars, typval_T *rettv, int map)
         }
         idx++;
       }
+      tv_list_set_lock(l, prev_lock);
     }
 
     restore_vimvar(VV_KEY, &save_key);
diff --git a/src/nvim/testdir/test_filter_map.vim b/src/nvim/testdir/test_filter_map.vim
index a52a66ac2f..1cd3a2287b 100644
--- a/src/nvim/testdir/test_filter_map.vim
+++ b/src/nvim/testdir/test_filter_map.vim
@@ -88,4 +88,14 @@ func Test_map_filter_fails()
   call assert_fails("let l = filter('abc', '\"> \" . v:val')", 'E896:')
 endfunc
 
+func Test_map_and_modify()
+  let l = ["abc"]
+  " cannot change the list halfway a map()
+  call assert_fails('call map(l, "remove(l, 0)[0]")', 'E741:')
+
+  let d = #{a: 1, b: 2, c: 3}
+  call assert_fails('call map(d, "remove(d, v:key)[0]")', 'E741:')
+  call assert_fails('echo map(d, {k,v -> remove(d, k)})', 'E741:')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab