vim-patch:9.1.1027: no sanitize check when running linematch

Problem:  no sanitize check when running linematch
Solution: add sanitize check before applying the linematch algorithm,
          similar to diff_find_change() (Jonathon)

closes: vim/vim#16446

https://github.com/vim/vim/commit/ca307efe486670b76563a4a287bc94dace57fb74

Co-authored-by: Jonathon <jonathonwhite@protonmail.com>

3 files changed, 68 insertions, 10 deletions

diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index ee063a330e..68441f7adc 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -2127,7 +2127,8 @@ int diff_check_with_linestatus(win_T *wp, linenr_T lnum, int *linestatus)
   // Useful for scrollbind calculations which need to count all the filler lines
   // above the screen.
   if (lnum >= wp->w_topline && lnum < wp->w_botline
-      && !dp->is_linematched && diff_linematch(dp)) {
+      && !dp->is_linematched && diff_linematch(dp)
+      && diff_check_sanity(curtab, dp)) {
     run_linematch_algorithm(dp);
   }
 
diff --git a/test/functional/ui/linematch_spec.lua b/test/functional/ui/linematch_spec.lua
index b564c01eaa..3593604c49 100644
--- a/test/functional/ui/linematch_spec.lua
+++ b/test/functional/ui/linematch_spec.lua
@@ -1147,4 +1147,32 @@ describe('regressions', function()
       },
     }
   end)
+
+  -- oldtest: Test_linematch_3diffs_sanity_check()
+  it('sanity check with 3 diff buffers', function()
+    clear()
+    screen = Screen.new(75, 20)
+    n.api.nvim_buf_set_lines(0, 0, -1, false, { 'abcd', 'def', 'hij' })
+    n.exec('rightbelow vnew')
+    n.api.nvim_buf_set_lines(0, 0, -1, false, { 'defq', 'hijk', 'nopq' })
+    n.exec('rightbelow vnew')
+    n.api.nvim_buf_set_lines(0, 0, -1, false, { 'hijklm', 'nopqr', 'stuv' })
+    n.exec([[
+      set diffopt+=linematch:60
+      windo diffthis | wincmd t
+      call feedkeys("Aq\<esc>")
+      call feedkeys("GAklm\<esc>")
+      call feedkeys("o")
+    ]])
+    screen:expect([[
+      {7:  }{22:abcdq                 }│{7:  }{23:----------------------}│{7:  }{23:-----------------------}|
+      {7:  }{4:def                   }│{7:  }{4:def}{27:q}{4:                  }│{7:  }{23:-----------------------}|
+      {7:  }{4:hijk}{27:lm}{4:                }│{7:  }{4:hijk                  }│{7:  }{4:hijk}{27:lm}{4:                 }|
+      {7:  }{23:----------------------}│{7:  }{4:nopq                  }│{7:  }{4:nopq}{27:r}{4:                  }|
+      {7:  }{4:^                      }│{7:  }{23:----------------------}│{7:  }{27:stuv}{4:                   }|
+      {1:~                       }│{1:~                       }│{1:~                        }|*13
+      {3:[No Name] [+]            }{2:[No Name] [+]            [No Name] [+]            }|
+      {5:-- INSERT --}                                                               |
+    ]])
+  end)
 end)
diff --git a/test/old/testdir/test_diffmode.vim b/test/old/testdir/test_diffmode.vim
index b452be5061..ab64658bd0 100644
--- a/test/old/testdir/test_diffmode.vim
+++ b/test/old/testdir/test_diffmode.vim
@@ -1247,7 +1247,7 @@ func CloseoffSetup()
   call setline(1, ['one', 'tow', 'three'])
   diffthis
   call assert_equal(1, &diff)
-  only!
+  bw!
 endfunc
 
 func Test_diff_closeoff()
@@ -2278,7 +2278,8 @@ func Test_diffget_diffput_linematch()
   call term_sendkeys(buf, "17gg")
   call term_sendkeys(buf, ":diffput\<CR>")
   call VerifyScreenDump(buf, 'Test_diff_get_put_linematch_19', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
 func Test_linematch_diff()
@@ -2298,7 +2299,8 @@ func Test_linematch_diff()
       \ 'abc d!',
       \ 'd!'])
   call VerifyScreenDump(buf, 'Test_linematch_diff1', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
 func Test_linematch_diff_iwhite()
@@ -2324,7 +2326,8 @@ func Test_linematch_diff_iwhite()
   call VerifyScreenDump(buf, 'Test_linematch_diff_iwhite1', {})
   call term_sendkeys(buf, ":set diffopt+=iwhiteall\<CR>")
   call VerifyScreenDump(buf, 'Test_linematch_diff_iwhite2', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
 func Test_linematch_diff_grouping()
@@ -2361,7 +2364,8 @@ func Test_linematch_diff_grouping()
       \ '?C',
       \ '?C'])
   call VerifyScreenDump(buf, 'Test_linematch_diff_grouping2', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
 func Test_linematch_diff_scroll()
@@ -2392,11 +2396,10 @@ func Test_linematch_diff_scroll()
   call VerifyScreenDump(buf, 'Test_linematch_diff_grouping_scroll1', {})
   call term_sendkeys(buf, "3\<c-e>")
   call VerifyScreenDump(buf, 'Test_linematch_diff_grouping_scroll2', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
-
-
 func Test_linematch_line_limit_exceeded()
   CheckScreendump
   call delete('.Xdifile1.swp')
@@ -2443,7 +2446,8 @@ func Test_linematch_line_limit_exceeded()
   " alignment algorithm will run on the largest diff block here
   call term_sendkeys(buf, ":set diffopt+=linematch:30\<CR>")
   call VerifyScreenDump(buf, 'Test_linematch_line_limit_exceeded2', {})
-
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 
 func Test_linematch_3diffs()
@@ -2480,6 +2484,31 @@ func Test_linematch_3diffs()
         \ "      BBB",
         \ "      BBB"])
   call VerifyScreenDump(buf, 'Test_linematch_3diffs1', {})
+  " clean up
+  call StopVimInTerminal(buf)
+endfunc
 
+" this used to access invalid memory
+func Test_linematch_3diffs_sanity_check()
+  CheckScreendump
+  call delete('.Xfile_linematch1.swp')
+  call delete('.Xfile_linematch2.swp')
+  call delete('.Xfile_linematch3.swp')
+  let lines =<< trim END
+    set diffopt+=linematch:60
+    call feedkeys("Aq\<esc>")
+    call feedkeys("GAklm\<esc>")
+    call feedkeys("o")
+  END
+  call writefile(lines, 'Xlinematch_3diffs.vim', 'D')
+  call writefile(['abcd', 'def', 'hij'], 'Xfile_linematch1', 'D')
+  call writefile(['defq', 'hijk', 'nopq'], 'Xfile_linematch2', 'D')
+  call writefile(['hijklm', 'nopqr', 'stuv'], 'Xfile_linematch3', 'D')
+  call WriteDiffFiles3(0, [], [], [])
+  let buf = RunVimInTerminal('-d -S Xlinematch_3diffs.vim Xfile_linematch1 Xfile_linematch2 Xfile_linematch3', {})
+  call VerifyScreenDump(buf, 'Test_linematch_3diffs2', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
 endfunc
 " vim: shiftwidth=2 sts=2 expandtab