man.vim: do not assume ftplugin is sourced before syntax

Fixes #5574

runtime/autoload/man.vim

@@ -50,11 +50,11 @@ function! man#open_page(count, count1, mods, ...) abort
     return
   endtry
   call s:push_tag()
-  let bufname = fnameescape('man://'.name.(empty(sect)?'':'('.sect.')'))
+  let bufname = 'man://'.name.(empty(sect)?'':'('.sect.')')
   if a:mods !~# 'tab' && s:find_man()
-    noautocmd execute 'silent edit' bufname
+    noautocmd execute 'silent edit' fnameescape(bufname)
   else
-    noautocmd execute 'silent' a:mods 'split' bufname
+    noautocmd execute 'silent' a:mods 'split' fnameescape(bufname)
   endif
   let b:man_sect = sect
   call s:read_page(path)
@@ -81,7 +81,7 @@ function! s:read_page(path) abort
   let cmd  = 'env MANPAGER=cat'.(empty($MANWIDTH) ? ' MANWIDTH='.winwidth(0) : '')
   let cmd .= ' '.s:man_cmd.' '.shellescape(a:path)
   silent put =system(cmd)
-  " remove all the backspaced text
+  " Remove all backspaced characters.
   execute 'silent keeppatterns keepjumps %substitute,.\b,,e'.(&gdefault?'':'g')
   while getline(1) =~# '^\s*$'
     silent keepjumps 1delete _
@@ -259,3 +259,22 @@ function! s:format_candidate(path, sect) abort
     return name.'('.sect.')'
   endif
 endfunction
+
+function! man#init_pager() abort
+  " Remove all backspaced characters.
+  execute 'silent keeppatterns keepjumps %substitute,.\b,,e'.(&gdefault?'':'g')
+  if getline(1) =~# '^\s*$'
+    silent keepjumps 1delete _
+  else
+    keepjumps 1
+  endif
+  " This is not perfect. See `man glDrawArraysInstanced`. Since the title is
+  " all caps it is impossible to tell what the original capitilization was.
+  let ref = tolower(matchstr(getline(1), '^\S\+'))
+  try
+    let b:man_sect = man#extract_sect_and_name_ref(ref)[0]
+  catch
+    let b:man_sect = ''
+  endtry
+  execute 'silent file man://'.fnameescape(ref)
+endfunction

runtime/ftplugin/man.vim

@@ -1,31 +1,15 @@
 " Maintainer:          Anmol Sethi <anmol@aubble.com>
 " Previous Maintainer: SungHyun Nam <goweol@gmail.com>
 
-if exists('b:did_ftplugin') || &filetype !=# 'man'
+if exists('b:did_ftplugin')
   finish
 endif
 let b:did_ftplugin = 1
 
-let s:pager = 0
+let s:pager = !exists('b:man_sect')
 
-if has('vim_starting')
-  let s:pager = 1
-  " remove all those backspaces
-  execute 'silent keeppatterns keepjumps %substitute,.\b,,e'.(&gdefault?'':'g')
-  if getline(1) =~# '^\s*$'
-    silent keepjumps 1delete _
-  else
-    keepjumps 1
-  endif
-  " This is not perfect. See `man glDrawArraysInstanced`. Since the title is
-  " all caps it is impossible to tell what the original capitilization was.
-  let ref = tolower(matchstr(getline(1), '^\S\+'))
-  try
-    let b:man_sect = man#extract_sect_and_name_ref(ref)[0]
-  catch
-    let b:man_sect = ''
-  endtry
-  execute 'silent file man://'.fnameescape(ref)
+if s:pager
+  call man#init_pager()
 endif
 
 setlocal buftype=nofile

runtime/syntax/man.vim

@@ -18,6 +18,9 @@ highlight default link manOptionDesc     Constant
 highlight default link manReference      PreProc
 highlight default link manSubHeading     Function
 
+if !exists('b:man_sect')
+  call man#init_pager()
+endif
 if b:man_sect =~# '^[23]'
   syntax include @c $VIMRUNTIME/syntax/c.vim
   syntax match manCFuncDefinition display '\<\h\w*\>\ze\(\s\|\n\)*(' contained