"nvim -es": disable shada #21723

Problem:
`nvim -es` (and `nvim -Es`) is the recommended way to non-interactively
run commands/vimscript. But it enables shada by default, which is
usually not wanted.

Solution:
- Disable shada by default for `nvim -es/-Es`. This can be overridden by
  `-i foo` if needed.
- Do NOT change the 'loadplugins' default.
  - User config + packages _should_ be enabled by default, for both `nvim
    -es` and `nvim -l`. Else any Lua packages you have can't be accessed
    without `-u path/to/config`, which is clumsy.
      - Use-cases:
        ```
        nvim --headless "+Lazy! sync" +qa
            would become: nvim -es "+Lazy! sync"
        nvim --headless +PlugInstall +qall
            would become: nvim -es +PlugInstall
        ```
  - Opt-out (`--clean` or `-u NONE`) is much easier than opt-in (`-u
    path/to/config`).
  -  User config/packages are analogous to pip packages, which are
     expected when doing `python -c ...`.

related: 7c94bcd2d7
related: ddd0eb6f51

test/functional/core/startup_spec.lua

@@ -136,7 +136,11 @@ describe('startup', function()
       vim.list_extend(args, { '-l', (script or 'test/functional/fixtures/startup.lua') })
       vim.list_extend(args, lua_args or {})
       local out = fn.system(args, input):gsub('\r\n', '\n')
-      return eq(dedent(expected), out)
+      if type(expected) == 'function' then
+        return expected(out)
+      else
+        return eq(dedent(expected), out)
+      end
     end
 
     it('failure modes', function()
@@ -172,6 +176,7 @@ describe('startup', function()
     it('Lua-error sets Nvim exitcode', function()
       local proc = n.spawn_wait('-l', 'test/functional/fixtures/startup-fail.lua')
       matches('E5113: .* my pearls!!', proc:output())
+      eq(0, proc.signal)
       eq(1, proc.status)
 
       eq(0, eval('v:shell_error'))
@@ -282,14 +287,30 @@ describe('startup', function()
       eq(0, eval('v:shell_error'))
     end)
 
-    it('disables swapfile/shada/config/plugins', function()
+    it('disables swapfile/shada/config/plugins unless overridden', function()
+      local script = [[print(('updatecount=%d shadafile=%s loadplugins=%s scripts=%d'):format(
+                       vim.o.updatecount, vim.o.shadafile, tostring(vim.o.loadplugins), math.max(1, #vim.fn.getscriptinfo())))]]
+      finally(function()
+        os.remove('Xtest_shada')
+      end)
+
       assert_l_out(
         'updatecount=0 shadafile=NONE loadplugins=false scripts=1\n',
         nil,
         nil,
         '-',
-        [[print(('updatecount=%d shadafile=%s loadplugins=%s scripts=%d'):format(
-          vim.o.updatecount, vim.o.shadafile, tostring(vim.o.loadplugins), math.max(1, #vim.fn.getscriptinfo())))]]
+        script
+      )
+
+      -- User can override.
+      assert_l_out(
+        function(out)
+          return matches('updatecount=99 shadafile=Xtest_shada loadplugins=true scripts=2%d\n', out)
+        end,
+        { '+set updatecount=99', '-i', 'Xtest_shada', '+set loadplugins', '-u', 'NORC' },
+        nil,
+        '-',
+        script
       )
     end)
   end)
@@ -572,19 +593,21 @@ describe('startup', function()
     eq('  encoding=utf-8\n', fn.system({ nvim_prog, '-n', '-es' }, { 'set encoding', '' }))
   end)
 
-  it('-es/-Es disables swapfile, user config #8540', function()
+  it('-es/-Es disables swapfile/shada/config #8540', function()
     for _, arg in ipairs({ '-es', '-Es' }) do
       local out = fn.system({
         nvim_prog,
         arg,
-        '+set swapfile? updatecount? shadafile?',
+        '+set updatecount? shadafile? loadplugins?',
         '+put =map(getscriptinfo(), {-> v:val.name})',
         '+%print',
       })
       local line1 = string.match(out, '^.-\n')
       -- updatecount=0 means swapfile was disabled.
-      eq('  swapfile  updatecount=0  shadafile=\n', line1)
-      -- Standard plugins were loaded, but not user config.
+      eq('  updatecount=0  shadafile=NONE  loadplugins\n', line1)
+      -- Standard plugins were loaded, but not user config. #31878
+      local nrlines = #vim.split(out, '\n')
+      ok(nrlines > 20, '>20', nrlines)
       ok(string.find(out, 'man.lua') ~= nil)
       ok(string.find(out, 'init.vim') == nil)
     end