patch 9.1.0204: Backspace inserts spaces with virtual text and 'smarttab'

Problem:  Backspace inserts spaces with virtual text and 'smarttab'.
Solution: Ignore virtual text and wrapping when backspacing.
          (zeertzjq)

related: neovim/neovim#28005
closes: #14296

Co-authored-by: VanaIgr <vanaigranov@gmail.com>
Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/edit.c

@@ -3958,10 +3958,9 @@ ins_del(void)
  * Delete one character for ins_bs().
  */
     static void
-ins_bs_one(colnr_T *vcolp)
+ins_bs_one(void)
 {
     dec_cursor();
-    getvcol(curwin, &curwin->w_cursor, vcolp, NULL, NULL);
     if (State & REPLACE_FLAG)
     {
 	// Don't delete characters before the insert point when in
@@ -4212,19 +4211,38 @@ ins_bs(
 				    || arrow_used))))))
 	{
 	    int		ts;
-	    colnr_T	vcol;
+	    colnr_T	vcol = 0;
 	    colnr_T	want_vcol;
-	    colnr_T	start_vcol;
+	    char_u	*line;
+	    char_u	*ptr;
+	    char_u	*end_ptr;
+	    char_u	*space_ptr;
+	    colnr_T	space_vcol = 0;
+	    int		prev_space = FALSE;
+	    colnr_T	want_col;
 
 	    *inserted_space_p = FALSE;
-	    // Compute the virtual column where we want to be.  Since
+
-	    // 'showbreak' may get in the way, need to get the last column of
+	    space_ptr = ptr = line = ml_get_curline();
-	    // the previous character.
+	    end_ptr = line + curwin->w_cursor.col;
-	    getvcol(curwin, &curwin->w_cursor, &vcol, NULL, NULL);
+
-	    start_vcol = vcol;
+	    // Find the last whitespace that is preceded by non-whitespace.
-	    dec_cursor();
+	    // Use chartabsize() so that virtual text and wrapping are ignored.
-	    getvcol(curwin, &curwin->w_cursor, NULL, NULL, &want_vcol);
+	    do {
-	    inc_cursor();
+		int	cur_space = VIM_ISWHITE(*ptr);
+
+		if (!prev_space && cur_space)
+		{
+		    space_ptr = ptr;
+		    space_vcol = vcol;
+		}
+		vcol += chartabsize(ptr, vcol);
+		MB_PTR_ADV(ptr);
+		prev_space = cur_space;
+	    } while (ptr < end_ptr);
+
+	    // Compute the virtual column where we want to be.
+	    want_vcol = vcol - 1;
 #ifdef FEAT_VARTABS
 	    if (p_sta && in_indent)
 	    {
@@ -4242,13 +4260,25 @@ ins_bs(
 	    want_vcol = (want_vcol / ts) * ts;
 #endif
 
-	    // delete characters until we are at or before want_vcol
+	    // Find the position to stop backspacing.
-	    while (vcol > want_vcol && curwin->w_cursor.col > 0
+	    // Use chartabsize() so that virtual text and wrapping are ignored.
-		    && (cc = *(ml_get_cursor() - 1), VIM_ISWHITE(cc)))
+	    while (TRUE)
-		ins_bs_one(&vcol);
+	    {
+		int size = chartabsize(space_ptr, space_vcol);
 
-	    // insert extra spaces until we are at want_vcol
+		if (space_vcol + size > want_vcol)
-	    while (vcol < want_vcol)
+		    break;
+		space_vcol += size;
+		MB_PTR_ADV(space_ptr);
+	    }
+	    want_col = space_ptr - line;
+
+	    // Delete characters until we are at or before want_col.
+	    while (curwin->w_cursor.col > want_col)
+		ins_bs_one();
+
+	    // Insert extra spaces until we are at want_vcol.
+	    for (; space_vcol < want_vcol; space_vcol++)
 	    {
 		// Remember the first char we inserted
 		if (curwin->w_cursor.lnum == Insstart_orig.lnum
@@ -4263,13 +4293,7 @@ ins_bs(
 		    if ((State & REPLACE_FLAG))
 			replace_push(NUL);
 		}
-		getvcol(curwin, &curwin->w_cursor, &vcol, NULL, NULL);
 	    }
-
-	    // If we are now back where we started delete one character.  Can
-	    // happen when using 'sts' and 'linebreak'.
-	    if (vcol >= start_vcol)
-		ins_bs_one(&vcol);
 	}
 
 	/*

src/testdir/test_edit.vim

@@ -6,8 +6,6 @@ endif
 
 source check.vim
 source screendump.vim
-
-" Needed for testing basic rightleft: Test_edit_rightleft
 source view_util.vim
 
 " Needs to come first until the bug in getchar() is
@@ -2158,4 +2156,113 @@ func Test_edit_Ctrl_RSB()
   bwipe!
 endfunc
 
+func s:check_backspace(expected)
+  let g:actual = []
+  inoremap <buffer> <F2> <Cmd>let g:actual += [getline('.')]<CR>
+  set backspace=indent,eol,start
+
+  exe "normal $i" .. repeat("\<BS>\<F2>", len(a:expected))
+  call assert_equal(a:expected, g:actual)
+
+  set backspace&
+  iunmap <buffer> <F2>
+  unlet g:actual
+endfunc
+
+" Test that backspace works with 'smarttab' and mixed Tabs and spaces.
+func Test_edit_backspace_smarttab_mixed()
+  call NewWindow(1, 30)
+  setlocal smarttab tabstop=4 shiftwidth=4
+  call setline(1, "\t    \t         \t a")
+  call s:check_backspace([
+        \ "\t    \t         \ta",
+        \ "\t    \t        a",
+        \ "\t    \t    a",
+        \ "\t    \ta",
+        \ "\t    a",
+        \ "\ta",
+        \ "a",
+        \ ])
+
+  call CloseWindow()
+endfunc
+
+" Test that backspace works with 'smarttab' and 'varsofttabstop'.
+func Test_edit_backspace_smarttab_varsofttabstop()
+  CheckFeature vartabs
+
+  call NewWindow(1, 30)
+  setlocal smarttab tabstop=8 varsofttabstop=6,2,5,3
+  call setline(1, "a\t    \t a")
+  call s:check_backspace([
+        \ "a\t    \ta",
+        \ "a\t     a",
+        \ "a\ta",
+        \ "a     a",
+        \ "aa",
+        \ "a",
+        \ ])
+
+  call CloseWindow()
+endfunc
+
+" Test that backspace works with 'smarttab' when a Tab is shown as "^I".
+func Test_edit_backspace_smarttab_list()
+  call NewWindow(1, 30)
+  setlocal smarttab tabstop=4 shiftwidth=4 list listchars=
+  call setline(1, "\t    \t         \t a")
+  call s:check_backspace([
+        \ "\t    \t        a",
+        \ "\t    \t    a",
+        \ "\t    \ta",
+        \ "\t  a",
+        \ "a",
+        \ ])
+
+  call CloseWindow()
+endfunc
+
+" Test that backspace works with 'smarttab' and 'breakindent'.
+func Test_edit_backspace_smarttab_breakindent()
+  CheckFeature linebreak
+
+  call NewWindow(3, 17)
+  setlocal smarttab tabstop=4 shiftwidth=4 breakindent breakindentopt=min:5
+  call setline(1, "\t    \t         \t a")
+  call s:check_backspace([
+        \ "\t    \t         \ta",
+        \ "\t    \t        a",
+        \ "\t    \t    a",
+        \ "\t    \ta",
+        \ "\t    a",
+        \ "\ta",
+        \ "a",
+        \ ])
+
+  call CloseWindow()
+endfunc
+
+" Test that backspace works with 'smarttab' and virtual text.
+func Test_edit_backspace_smarttab_virtual_text()
+  CheckFeature textprop
+
+  call NewWindow(1, 50)
+  setlocal smarttab tabstop=4 shiftwidth=4
+  call setline(1, "\t    \t         \t a")
+  call prop_type_add('theprop', {})
+  call prop_add(1, 3, {'type': 'theprop', 'text': 'text'})
+  call s:check_backspace([
+        \ "\t    \t         \ta",
+        \ "\t    \t        a",
+        \ "\t    \t    a",
+        \ "\t    \ta",
+        \ "\t    a",
+        \ "\ta",
+        \ "a",
+        \ ])
+
+  call CloseWindow()
+  call prop_type_delete('theprop')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    204,
 /**/
     203,
 /**/