patch 8.2.4960: text properties that cross lines not updated for deleted line

Problem:    Text properties that cross line boundary are not correctly updated
            for a deleted line.
Solution:   Correct computing location of text property entry. (Paul Ollis,
            closes #10431, closes #10430)

src/memline.c

@@ -3501,8 +3501,9 @@ ml_replace_len(
 #ifdef FEAT_PROP_POPUP
 /*
  * Adjust text properties in line "lnum" for a deleted line.
- * When "above" is true this is the line above the deleted line.
+ * When "above" is true this is the line above the deleted line, otherwise this
- * "del_props" are the properties of the deleted line.
+ * is the line below the deleted line.
+ * "del_props[del_props_len]" are the properties of the deleted line.
  */
     static void
 adjust_text_props_for_delete(
@@ -3569,7 +3570,7 @@ adjust_text_props_for_delete(
 							   : TP_FLAG_CONT_PREV;
 		textprop_T  prop_this;
 
-		mch_memmove(&prop_this, text + textlen + done_del,
+		mch_memmove(&prop_this, text + textlen + done_this,
 							   sizeof(textprop_T));
 		if ((prop_this.tp_flags & flag)
 			&& prop_del.tp_id == prop_this.tp_id
@@ -3577,7 +3578,7 @@ adjust_text_props_for_delete(
 		{
 		    found = TRUE;
 		    prop_this.tp_flags &= ~flag;
-		    mch_memmove(text + textlen + done_del, &prop_this,
+		    mch_memmove(text + textlen + done_this, &prop_this,
 							   sizeof(textprop_T));
 		    break;
 		}

src/testdir/test_textprop.vim

@@ -1645,6 +1645,57 @@ def Test_prop_add_delete_line()
   bwipe!
 enddef
 
+" This test is to detect a regression related to #10430. It is not an attempt
+" fully cover deleting lines in the presence of multi-line properties.
+def Test_delete_line_within_multiline_prop()
+  new
+  setline(1, '# Top.')
+  append(1, ['some_text = """', 'A string.', '"""', '# Bottom.'])
+  prop_type_add('Identifier', {'highlight': 'ModeMsg', 'priority': 0, 'combine': 0, 'start_incl': 0, 'end_incl': 0})
+  prop_type_add('String', {'highlight': 'MoreMsg', 'priority': 0, 'combine': 0, 'start_incl': 0, 'end_incl': 0})
+  prop_add(2, 1, {'type': 'Identifier', 'end_lnum': 2, 'end_col': 9})
+  prop_add(2, 13, {'type': 'String', 'end_lnum': 4, 'end_col': 4})
+
+  # The property for line 3 should extend into the previous and next lines.
+  var props = prop_list(3)
+  var prop = props[0]
+  assert_equal(1, len(props))
+  assert_equal(0, prop['start'])
+  assert_equal(0, prop['end'])
+
+  # This deletion should run without raising an exception.
+  try
+    :2 del
+  catch
+    assert_report('Line delete should have workd, but it raised an error.')
+  endtry
+
+  # The property for line 2 (was 3) should no longer extend into the previous
+  # line.
+  props = prop_list(2)
+  prop = props[0]
+  assert_equal(1, len(props))
+  assert_equal(1, prop['start'], 'Property was not changed to start within the line.')
+
+  # This deletion should run without raising an exception.
+  try
+    :3 del
+  catch
+    assert_report('Line delete should have workd, but it raised an error.')
+  endtry
+
+  # The property for line 2 (originally 3) should no longer extend into the next
+  # line.
+  props = prop_list(2)
+  prop = props[0]
+  assert_equal(1, len(props))
+  assert_equal(1, prop['end'], 'Property was not changed to end within the line.')
+
+  prop_type_delete('Identifier')
+  prop_type_delete('String')
+  bwip!
+enddef
+
 func Test_prop_in_linebreak()
   CheckRunVimInTerminal
 

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4960,
 /**/
     4959,
 /**/