man.vim: fixes to argument handling and parsing

- Define a collection of legal characters when parsing page and section
  in `s:parse_page_and_section()` instead of relying on 'iskeyword',
  which is unreliable.
- Allow non-numeric section names (e.g., `3c`).
- Simplify argument handling in `man#get_page()` to accommodate
  non-numeric section names.

Fixes #4165.

runtime/autoload/man.vim

@@ -11,6 +11,8 @@ catch /E145:/
   " Ignore the error in restricted mode
 endtry
 
+" Load man page {page} from {section}
+"   call man#get_page([{section}, ]{page})
 function man#get_page(...) abort
   let invoked_from_man = (&filetype ==# 'man')
 
@@ -20,21 +22,14 @@ function man#get_page(...) abort
   elseif a:0 > 2
     echoerr 'too many arguments'
     return
-  elseif a:0 == 2
-    let [page, sect] = [a:2, 0 + a:1]
-  elseif type(1) == type(a:1)
-    let [page, sect] = ['<cword>', a:1]
-  else
-    let [page, sect] = [a:1, '']
   endif
 
-  if page == '<cword>'
-    let page = expand('<cword>')
-  endif
+  let sect = get(a:000, 0)
+  let page = get(a:000, 1, sect)
 
   let [page, sect] = s:parse_page_and_section(sect, page)
 
-  if 0 + sect > 0 && s:find_page(sect, page) == 0
+  if !empty(sect) && s:find_page(sect, page) == 0
     let sect = ''
   endif
 
@@ -118,15 +113,11 @@ endfunction
 " Expects a string like 'access' or 'access(2)'.
 function s:parse_page_and_section(sect, str) abort
   try
-    let save_isk = &iskeyword
-    setlocal iskeyword-=(,)
-    let page = substitute(a:str, '(*\(\k\+\).*', '\1', '')
-    let sect = substitute(a:str, '\(\k\+\)(\([^()]*\)).*', '\2', '')
-    if sect == page || -1 == match(sect, '^[0-9 ]\+$')
+    let [page, sect] = matchlist(a:str, '\v\C([-.[:alnum:]_]+)%(\(([-.[:alnum:]_]+)\))?')[1:2]
+    if empty(sect)
       let sect = a:sect
     endif
   catch
-    let &l:iskeyword = save_isk
     echoerr 'man.vim: failed to parse: "'.a:str.'"'
   endtry
 
@@ -134,7 +125,7 @@ function s:parse_page_and_section(sect, str) abort
 endfunction
 
 function s:cmd(sect, page) abort
-  if 0 + a:sect > 0
+  if !empty(a:sect)
     return s:man_sect_arg.' '.a:sect.' '.a:page
   endif
   return a:page

runtime/ftplugin/man.vim

@@ -24,11 +24,11 @@ setlocal buftype=nofile noswapfile
 setlocal nomodifiable readonly bufhidden=hide nobuflisted tabstop=8
 
 if !exists("g:no_plugin_maps") && !exists("g:no_man_maps")
-  nnoremap <silent> <buffer> <C-]>    :call man#get_page(v:count)<CR>
+  nnoremap <silent> <buffer> <C-]>    :call man#get_page(v:count, expand('<cword>'))<CR>
   nnoremap <silent> <buffer> <C-T>    :call man#pop_page()<CR>
   nnoremap <silent> <nowait><buffer>  q <C-W>c
   if &keywordprg !=# ':Man'
-    nnoremap <silent> <buffer> K      :call man#get_page(v:count)<CR>
+    nnoremap <silent> <buffer> K      :call man#get_page(v:count, expand('<cword>'))<CR>
   endif
 endif