mark: Make sure that jumplist item will not have zero lnum

Fixes neovim#7169

Author: ZyX-I

Diff for: src/nvim/mark.c

@@ -171,6 +171,10 @@ void setpcmark(void)
   curwin->w_prev_pcmark = curwin->w_pcmark;
   curwin->w_pcmark = curwin->w_cursor;
 
+  if (curwin->w_pcmark.lnum == 0) {
+    curwin->w_pcmark.lnum = 1;
+  }
+
   /* If jumplist is full: remove oldest entry */
   if (++curwin->w_jumplistlen > JUMPLISTSIZE) {
     curwin->w_jumplistlen = JUMPLISTSIZE;

Diff for: src/nvim/shada.c

@@ -2557,6 +2557,12 @@ static ShaDaWriteResult shada_write(ShaDaWriteDef *const sd_writer,
     xfmark_T fm;
     jump_iter = mark_jumplist_iter(jump_iter, curwin, &fm);
 
+    if (fm.fmark.mark.lnum == 0) {
+      iemsgf("ShaDa: mark lnum zero (ji:%p, js:%p, len:%i)",
+             (void *)jump_iter, (void *)&curwin->w_jumplist[0],
+             curwin->w_jumplistlen);
+      continue;
+    }
     const buf_T *const buf = (fm.fmark.fnum == 0
                               ? NULL
                               : buflist_findnr(fm.fmark.fnum));

Diff for: test/functional/shada/helpers.lua

@@ -6,15 +6,14 @@ local write_file, merge_args = helpers.write_file, helpers.merge_args
 local mpack = require('mpack')
 
 local tmpname = helpers.tmpname()
-local additional_cmd = ''
+local append_argv = nil
 
-local function nvim_argv(shada_file)
+local function nvim_argv(shada_file, embed)
   local argv = {nvim_prog, '-u', 'NONE', '-i', shada_file or tmpname, '-N',
                 '--cmd', 'set shortmess+=I background=light noswapfile',
-                '--cmd', additional_cmd,
-                '--embed'}
-  if helpers.prepend_argv then
-    return merge_args(helpers.prepend_argv, argv)
+                embed or '--embed'}
+  if helpers.prepend_argv or append_argv then
+    return merge_args(helpers.prepend_argv, argv, append_argv)
   else
     return argv
   end
@@ -26,12 +25,21 @@ local reset = function(shada_file)
 end
 
 local set_additional_cmd = function(s)
-  additional_cmd = s
+  append_argv = {'--cmd', s}
+end
+
+local function add_argv(...)
+  if select('#', ...) == 0 then
+    append_argv = nil
+  else
+    append_argv = {...}
+  end
 end
 
 local clear = function()
+  os.execute('cp ' .. tmpname .. ' /tmp/test.shada')
   os.remove(tmpname)
-  set_additional_cmd('')
+  append_argv = nil
 end
 
 local get_shada_rw = function(fname)
@@ -80,7 +88,9 @@ end
 return {
   reset=reset,
   set_additional_cmd=set_additional_cmd,
+  add_argv=add_argv,
   clear=clear,
   get_shada_rw=get_shada_rw,
   read_shada_file=read_shada_file,
+  nvim_argv=nvim_argv,
 }

Diff for: test/functional/shada/marks_spec.lua

@@ -9,6 +9,8 @@ local shada_helpers = require('test.functional.shada.helpers')
 local reset, set_additional_cmd, clear =
   shada_helpers.reset, shada_helpers.set_additional_cmd,
   shada_helpers.clear
+local add_argv = shada_helpers.add_argv
+local nvim_argv = shada_helpers.nvim_argv
 
 local nvim_current_line = function()
   return curwinmeths.get_cursor()[1]
@@ -17,8 +19,10 @@ end
 describe('ShaDa support code', function()
   local testfilename = 'Xtestfile-functional-shada-marks'
   local testfilename_2 = 'Xtestfile-functional-shada-marks-2'
+  local non_existent_testfilename = testfilename .. '.nonexistent'
   before_each(function()
     reset()
+    os.remove(non_existent_testfilename)
     local fd = io.open(testfilename, 'w')
     fd:write('test\n')
     fd:write('test2\n')
@@ -214,4 +218,23 @@ describe('ShaDa support code', function()
     nvim_command('" sync 2')
     eq(2, nvim_current_line())
   end)
+
+  -- -c temporary sets lnum to zero to make `+/pat` work, so calling setpcmark()
+  -- during -c used to add item with zero lnum to jump list.
+  it('does not create incorrect file for non-existent buffers when writing from -c',
+  function()
+    add_argv('--cmd', 'silent edit ' .. non_existent_testfilename, '-c', 'qall')
+    local argv = nvim_argv(nil, '--headless')
+    eq('', funcs.system(argv))
+    eq(0, exc_exec('rshada'))
+  end)
+
+  it('does not create incorrect file for non-existent buffers opened from -c',
+  function()
+    add_argv('-c', 'silent edit ' .. non_existent_testfilename,
+             '-c', 'autocmd VimEnter * qall')
+    local argv = nvim_argv(nil, '--headless')
+    eq('', funcs.system(argv))
+    eq(0, exc_exec('rshada'))
+  end)
 end)