Make generation functions compatible with older vims.

PR #634, PR #635, and PR #636 introduced new features that broke
compatibility with older version of Vim. This modifies those changes to
ensure compatibility. Closes #781.

Removes usage of funcref(), closure. Fixes filter() call.
Made globpath calls not use the list argument.
Unlet a variable that is reused (sticky type checking)

v7.4.1989 modified filter() to accept a Funcref
v7.4.2120 Added function "closure" argument
v7.4.2137 add funcref()

autoload/vimwiki/base.vim

@@ -380,7 +380,8 @@ endfunction
 
 function! vimwiki#base#generate_links(create)
 
-  function! Generator() closure
+  let GeneratorLinks = copy(l:)
+  function! GeneratorLinks.f()
     let lines = []
 
     let links = vimwiki#base#get_wikilinks(vimwiki#vars#get_bufferlocal('wiki_nr'), 0)
@@ -413,7 +414,7 @@ function! vimwiki#base#generate_links(create)
   let links_rx = '\%(^\s*$\)\|\%('.vimwiki#vars#get_syntaxlocal('rxListBullet').'\)'
 
   call vimwiki#base#update_listing_in_buffer(
-        \ funcref('Generator'),
+        \ GeneratorLinks,
         \ vimwiki#vars#get_global('links_header'),
         \ links_rx,
         \ line('$')+1,
@@ -489,17 +490,15 @@ function! vimwiki#base#find_files(wiki_nr, directories_only)
   else
     let pattern = '**/*'.ext
   endif
-  let files = globpath(root_directory, pattern, 0, 1)
+  let files = split(globpath(root_directory, pattern))
+
   " filter excluded files before returning
-  function! ExcludeFiles(idx, val) closure
   for pattern in vimwiki#vars#get_wikilocal('exclude_files')
-      if index(globpath(root_directory, pattern, 0, 1), a:val) != -1
-        return 0
-      endif
+    let efiles = split(globpath(root_directory, pattern))
+    let files = filter(files, 'index(efiles, v:val) == -1')
   endfor
-    return 1
-  endfunction
-  return filter(files, funcref('ExcludeFiles'))
+
+  return files
 endfunction
 
 
@@ -1209,7 +1208,7 @@ function! vimwiki#base#update_listing_in_buffer(Generator, start_header,
       let lines_diff += 1
     endfor
   endif
-  for string in a:Generator()
+  for string in a:Generator.f()
     keepjumps call append(start_lnum - 1, string)
     let start_lnum += 1
     let lines_diff += 1
@@ -1999,15 +1998,18 @@ function! vimwiki#base#table_of_contents(create)
     endif
   endif
 
-  function! Generator() closure
+  " use a dictionary function for closure like capability
+  " copy all local variables into dict (add a: if arguments are needed)
+  let GeneratorTOC = copy(l:)
+  function! GeneratorTOC.f()
     let numbering = vimwiki#vars#get_global('html_header_numbering')
     let headers_levels = [['', 0], ['', 0], ['', 0], ['', 0], ['', 0], ['', 0]]
     let complete_header_infos = []
-    for header in headers
+    for header in self.headers
       let h_text = header[2]
       let h_level = header[1]
       " don't include the TOC's header itself
-      if h_text ==# toc_header_text
+      if h_text ==# self.toc_header_text
         continue
       endif
       let headers_levels[h_level-1] = [h_text, headers_levels[h_level-1][1]+1]
@@ -2050,7 +2052,7 @@ function! vimwiki#base#table_of_contents(create)
   let links_rx = '\%(^\s*$\)\|\%('.vimwiki#vars#get_syntaxlocal('rxListBullet').'\)'
 
   call vimwiki#base#update_listing_in_buffer(
-        \ funcref('Generator'),
+        \ GeneratorTOC,
         \ toc_header_text,
         \ links_rx,
         \ 1,

autoload/vimwiki/diary.vim

@@ -312,7 +312,8 @@ endfunction
 
 function! vimwiki#diary#generate_diary_section()
 
-  function! Generator() closure
+  let GeneratorDiary = copy(l:)
+  function! GeneratorDiary.f()
     let lines = []
 
     let links_with_captions = s:read_captions(s:get_diary_files())
@@ -392,7 +393,7 @@ function! vimwiki#diary#generate_diary_section()
           \ '\%(^\s*$\)\|\%('.vimwiki#vars#get_syntaxlocal('rxListBullet').'\)'
 
     call vimwiki#base#update_listing_in_buffer(
-          \ funcref('Generator'),
+          \ GeneratorDiary,
           \ vimwiki#vars#get_wikilocal('diary_header'),
           \ content_rx,
           \ 1,

autoload/vimwiki/tags.vim

@@ -303,8 +303,11 @@ function! vimwiki#tags#generate_tags(create, ...) abort
   let specific_tags = a:000
   let header_level = vimwiki#vars#get_global('tags_header_level')
 
-  function! Generator() closure
-    let need_all_tags = empty(specific_tags)
+  " use a dictionary function for closure like capability
+  " copy all local variables into dict (add a: if arguments are needed)
+  let GeneratorTags = copy(l:)
+  function! GeneratorTags.f()
+    let need_all_tags = empty(self.specific_tags)
     let metadata = s:load_tags_metadata()
 
     " make a dictionary { tag_name: [tag_links, ...] }
@@ -317,17 +320,18 @@ function! vimwiki#tags#generate_tags(create, ...) abort
           let tags_entries[entry.tagname] = [entry.link]
         endif
       endfor
+      unlet entry " needed for older vims with sticky type checking since name is reused
     endfor
 
     let lines = []
     let bullet = repeat(' ', vimwiki#lst#get_list_margin()).vimwiki#lst#default_symbol().' '
     for tagname in sort(keys(tags_entries))
-      if need_all_tags || index(specific_tags, tagname) != -1
+      if need_all_tags || index(self.specific_tags, tagname) != -1
         if len(lines) > 0
           call add(lines, '')
         endif
 
-        let tag_tpl = printf('rxH%d_Template', header_level + 1)
+        let tag_tpl = printf('rxH%d_Template', self.header_level + 1)
         call add(lines, s:safesubstitute(vimwiki#vars#get_syntaxlocal(tag_tpl), '__Header__', tagname, ''))
 
         if vimwiki#vars#get_wikilocal('syntax') == 'markdown'
@@ -363,7 +367,7 @@ function! vimwiki#tags#generate_tags(create, ...) abort
         \ '\%(^\s*$\)\|\%('.vimwiki#vars#get_syntaxlocal('rxListBullet').'\)'
 
   call vimwiki#base#update_listing_in_buffer(
-        \ funcref('Generator'),
+        \ GeneratorTags,
         \ vimwiki#vars#get_global('tags_header'),
         \ links_rx,
         \ line('$')+1,