patch 8.2.1698: cannot lock a variable in legacy Vim script like in Vim9v8.2.1698

Problem:    Cannot lock a variable in legacy Vim script like in Vim9.
Solution:   Make ":lockvar 0" work.

1 files changed, 36 insertions, 13 deletions

diff --git a/src/evalvars.c b/src/evalvars.c
index 1c40f4111f..5ceaca48a0 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -1560,9 +1560,9 @@ do_unlet_var(
 	*name_end = cc;
     }
     else if ((lp->ll_list != NULL
-		 && var_check_lock(lp->ll_list->lv_lock, lp->ll_name, FALSE))
+		 && value_check_lock(lp->ll_list->lv_lock, lp->ll_name, FALSE))
 	    || (lp->ll_dict != NULL
-		 && var_check_lock(lp->ll_dict->dv_lock, lp->ll_name, FALSE)))
+		&& value_check_lock(lp->ll_dict->dv_lock, lp->ll_name, FALSE)))
 	return FAIL;
     else if (lp->ll_range)
     {
@@ -1573,7 +1573,7 @@ do_unlet_var(
 	while (ll_li != NULL && (lp->ll_empty2 || lp->ll_n2 >= ll_n1))
 	{
 	    li = ll_li->li_next;
-	    if (var_check_lock(ll_li->li_tv.v_lock, lp->ll_name, FALSE))
+	    if (value_check_lock(ll_li->li_tv.v_lock, lp->ll_name, FALSE))
 		return FAIL;
 	    ll_li = li;
 	    ++ll_n1;
@@ -1646,7 +1646,7 @@ do_unlet(char_u *name, int forceit)
 	    di = HI2DI(hi);
 	    if (var_check_fixed(di->di_flags, name, FALSE)
 		    || var_check_ro(di->di_flags, name, FALSE)
-		    || var_check_lock(d->dv_lock, name, FALSE))
+		    || value_check_lock(d->dv_lock, name, FALSE))
 		return FAIL;
 
 	    delete_var(ht, hi);
@@ -1677,9 +1677,6 @@ do_lock_var(
     int		cc;
     dictitem_T	*di;
 
-    if (deep == 0)	// nothing to do
-	return OK;
-
     if (lp->ll_tv == NULL)
     {
 	cc = *name_end;
@@ -1710,11 +1707,16 @@ do_lock_var(
 		    di->di_flags |= DI_FLAGS_LOCK;
 		else
 		    di->di_flags &= ~DI_FLAGS_LOCK;
-		item_lock(&di->di_tv, deep, lock, FALSE);
+		if (deep != 0)
+		    item_lock(&di->di_tv, deep, lock, FALSE);
 	    }
 	}
 	*name_end = cc;
     }
+    else if (deep == 0)
+    {
+	// nothing to do
+    }
     else if (lp->ll_range)
     {
 	listitem_T    *li = lp->ll_li;
@@ -3007,8 +3009,13 @@ set_var_const(
 		    goto failed;
 	    }
 
+	    // Check in this order for backwards compatibility:
+	    // - Whether the variable is read-only
+	    // - Whether the variable value is locked
+	    // - Whether the variable is locked
 	    if (var_check_ro(di->di_flags, name, FALSE)
-			       || var_check_lock(di->di_tv.v_lock, name, FALSE))
+			    || value_check_lock(di->di_tv.v_lock, name, FALSE)
+			    || var_check_lock(di->di_flags, name, FALSE))
 		goto failed;
 	}
 	else
@@ -3158,6 +3165,22 @@ var_check_ro(int flags, char_u *name, int use_gettext)
 }
 
 /*
+ * Return TRUE if di_flags "flags" indicates variable "name" is locked.
+ * Also give an error message.
+ */
+    int
+var_check_lock(int flags, char_u *name, int use_gettext)
+{
+    if (flags & DI_FLAGS_LOCK)
+    {
+	semsg(_(e_variable_is_locked_str),
+				       use_gettext ? (char_u *)_(name) : name);
+	return TRUE;
+    }
+    return FALSE;
+}
+
+/*
  * Return TRUE if di_flags "flags" indicates variable "name" is fixed.
  * Also give an error message.
  */
@@ -3204,12 +3227,12 @@ var_wrong_func_name(
 }
 
 /*
- * Return TRUE if "flags" indicates variable "name" is locked (immutable).
- * Also give an error message, using "name" or _("name") when use_gettext is
- * TRUE.
+ * Return TRUE if "flags" indicates variable "name" has a locked (immutable)
+ * value.  Also give an error message, using "name" or _("name") when
+ * "use_gettext" is TRUE.
  */
     int
-var_check_lock(int lock, char_u *name, int use_gettext)
+value_check_lock(int lock, char_u *name, int use_gettext)
 {
     if (lock & VAR_LOCKED)
     {