From 88d4f255b7b7a19bb4f6489e0ad0956e47d51fed Mon Sep 17 00:00:00 2001
From: Gary Johnson <garyjohn@spocom.com>
Date: Sat, 1 Jun 2024 20:51:33 +0200
Subject: patch 9.1.0456: Left shift is incorrect with vartabstop and
 shiftwidth=0

Problem:  Left shift is incorrect with vartabstop and shiftwidth=0
Solution: make tabstop_at() function aware of shift direction
          (Gary Johnson)

The problem was that with 'vartabstop' set and 'shiftwidth' equal 0,
left shifts using << were shifting the line to the wrong column.  The
tabstop to the right of the first character in the line was being used
as the shift amount instead of the tabstop to the left of that first
character.

The reason was that the tabstop_at() function always returned the value
of the tabstop to the right of the given column and was not accounting
for the direction of the shift.

The solution was to make tabstop_at() aware of the direction of the
shift and to choose the tabtop accordingly.

A test was added to check this behavior and make sure it doesn't
regress.

While at it, also fix a few indentation/alignment issues.

fixes: #14864
closes: #14887

Signed-off-by: Gary Johnson <garyjohn@spocom.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/testdir/test_vartabs.vim | 59 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

(limited to 'src/testdir/test_vartabs.vim')

diff --git a/src/testdir/test_vartabs.vim b/src/testdir/test_vartabs.vim
index e15a072f72..bae00dd057 100644
--- a/src/testdir/test_vartabs.vim
+++ b/src/testdir/test_vartabs.vim
@@ -454,5 +454,64 @@ func Test_vartabstop_latin1()
   set nocompatible linebreak& list& revins& smarttab& vartabstop&
 endfunc
 
+" Verify that right-shifting and left-shifting adjust lines to the proper
+" tabstops.
+func Test_vartabstop_shift_right_left()
+  new
+  set expandtab
+  set shiftwidth=0
+  set vartabstop=17,11,7
+  exe "norm! aword"
+  let expect = "word"
+  call assert_equal(expect, getline(1))
+
+  " Shift to first tabstop.
+  norm! >>
+  let expect = "                 word"
+  call assert_equal(expect, getline(1))
+
+  " Shift to second tabstop.
+  norm! >>
+  let expect = "                            word"
+  call assert_equal(expect, getline(1))
+
+  " Shift to third tabstop.
+  norm! >>
+  let expect = "                                   word"
+  call assert_equal(expect, getline(1))
+
+  " Shift to fourth tabstop, repeating the third shift width.
+  norm! >>
+  let expect = "                                          word"
+  call assert_equal(expect, getline(1))
+
+  " Shift back to the third tabstop.
+  norm! <<
+  let expect = "                                   word"
+  call assert_equal(expect, getline(1))
+
+  " Shift back to the second tabstop.
+  norm! <<
+  let expect = "                            word"
+  call assert_equal(expect, getline(1))
+
+  " Shift back to the first tabstop.
+  norm! <<
+  let expect = "                 word"
+  call assert_equal(expect, getline(1))
+
+  " Shift back to the left margin.
+  norm! <<
+  let expect = "word"
+  call assert_equal(expect, getline(1))
+
+  " Shift again back to the left margin.
+  norm! <<
+  let expect = "word"
+  call assert_equal(expect, getline(1))
+
+  bwipeout!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab
-- 
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