fix(ui2): emit FileType event after setting default pager options #36315

Problem: Setting a filetype before configuring default options for ui2
buffers (pager, cmd, ...) prevents users from setting their own options.

Solution: Call nvim_set_option_value after defaults are set.

Closes #36314

Co-authored-by: Luuk van Baal <luukvbaal@gmail.com>

runtime/lua/vim/_extui/shared.lua

@@ -65,13 +65,9 @@ function M.check_targets()
     end
 
     if setopt then
-      local name = { cmd = 'Cmd', dialog = 'Dialog', msg = 'Msg', pager = 'Pager' }
+      -- Set options without firing OptionSet and BufFilePost.
-      -- Fire a FileType autocommand with window context to let the user reconfigure local options.
+      vim._with({ win = M.wins[type], noautocmd = true }, function()
-      -- First set 'eventignorewin' to avoid firing OptionSet and BufFilePost.
+        local ignore = 'all,-FileType' .. (type == 'pager' and ',-TextYankPost' or '')
-      api.nvim_win_call(M.wins[type], function()
-        local ft = name[type]:sub(1, 1):lower() .. name[type]:sub(2)
-        api.nvim_set_option_value('filetype', ft, { scope = 'local' })
-        local ignore = 'all' .. (type == 'pager' and ',-TextYankPost' or '')
         api.nvim_set_option_value('eventignorewin', ignore, { scope = 'local' })
         api.nvim_set_option_value('wrap', true, { scope = 'local' })
         api.nvim_set_option_value('linebreak', false, { scope = 'local' })
@@ -87,7 +83,11 @@ function M.check_targets()
           api.nvim_set_option_value('winhighlight', hl, { scope = 'local' })
         end
       end)
-      api.nvim_buf_set_name(M.bufs[type], ('[%s]'):format(name[type]))
+      api.nvim_buf_set_name(M.bufs[type], ('[%s]'):format(type:sub(1, 1):upper() .. type:sub(2)))
+      -- Fire FileType with window context to let the user reconfigure local options.
+      vim._with({ win = M.wins[type] }, function()
+        api.nvim_set_option_value('filetype', type, { scope = 'local' })
+      end)
 
       if type == 'pager' then
         -- Close pager with `q`, same as `checkhealth`

test/functional/ui/messages2_spec.lua

@@ -1,5 +1,6 @@
 -- Tests for (protocol-driven) ui2, intended to replace the legacy message grid UI.
 
+local t = require('test.testutil')
 local n = require('test.functional.testnvim')()
 local Screen = require('test.functional.ui.screen')
 
@@ -418,4 +419,23 @@ describe('messages2', function()
                                                            |
     ]])
   end)
+
+  it('FileType is fired after default options are set', function()
+    n.exec([[
+      let g:set = {}
+      au FileType pager set nowrap
+      au OptionSet * let g:set[expand('<amatch>')] = g:set->get(expand('<amatch>'), 0) + 1
+      echom 'foo'->repeat(&columns)
+      messages
+    ]])
+    screen:expect([[
+                                                           |
+      {1:~                                                    }|*9
+      {3:─────────────────────────────────────────────────────}|
+      ^foofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofoofo|
+      {1:                                                     }|
+                                                           |
+    ]])
+    t.eq({ filetype = 4 }, n.eval('g:set')) -- still fires for 'filetype'
+  end)
 end)