style: adhere to contributing guidelines and optimize core logic (#2748)

* style: adhere to contributing guidelines and optimize core logic

* plugin: adhere to coding style and fix initialization

plugin/airline.vim

@@ -6,7 +6,7 @@ set cpo&vim
 
 scriptencoding utf-8
 
-if &cp || v:version < 702 || (exists('g:loaded_airline') && g:loaded_airline)
+if &compatible || v:version < 702 || (exists('g:loaded_airline') && g:loaded_airline)
   finish
 endif
 let g:loaded_airline = 1
@@ -29,7 +29,7 @@ function! s:init()
       endif
       let palette = g:airline#themes#{g:airline_theme}#palette
     catch
-      call airline#util#warning(printf('Could not resolve airline theme "%s". Themes have been migrated to github.com/vim-airline/vim-airline-themes.', g:airline_theme))
+      call airline#util#warning(printf('Could not resolve airline theme "%s".', g:airline_theme))
       let g:airline_theme = 'dark'
     endtry
     try
@@ -59,13 +59,15 @@ function! s:on_window_changed(event)
     " do not trigger for previewwindows
     return
   endif
+
   let s:active_winnr = winnr()
   " Handle each window only once, since we might come here several times for
   " different autocommands.
-  let l:key = [bufnr('%'), s:active_winnr, winnr('$'), tabpagenr(), &ft]
+  let key = [bufnr('%'), s:active_winnr, winnr('$'), tabpagenr(), &filetype]
-  if get(g:, 'airline_last_window_changed', []) == l:key
+
-        \ && &stl is# '%!airline#statusline('.s:active_winnr.')'
+  if get(g:, 'airline_last_window_changed', []) == key
-        \ && &ft !~? 'gitcommit'
+        \ && &statusline is# '%!airline#statusline('.s:active_winnr.')'
+        \ && &filetype !~? 'gitcommit'
     " fugitive is special, it changes names and filetypes several times,
     " make sure the caching does not get into its way
     if a:event ==# 'BufUnload'
@@ -75,7 +77,8 @@ function! s:on_window_changed(event)
     endif
     return
   endif
-  let g:airline_last_window_changed = l:key
+
+  let g:airline_last_window_changed = key
   call s:init()
   call airline#update_statusline()
 
@@ -90,7 +93,8 @@ function! s:on_focus_gained()
   endif
 
   if airline#util#try_focusgained()
-    unlet! w:airline_lastmode | :call <sid>airline_refresh(1)
+    unlet! w:airline_lastmode
+    call s:airline_refresh(1)
   endif
 endfunction
 
@@ -108,8 +112,6 @@ function! s:on_colorscheme_changed()
   if !s:theme_in_vimrc
     call airline#switch_matching_theme()
   endif
-
-  " couldn't find a match, or theme was defined, just refresh
   call airline#load_theme()
 endfunction
 
@@ -120,18 +122,17 @@ endfunction
 function! s:airline_toggle()
   if exists("#airline")
     augroup airline
-      au!
+      autocmd!
     augroup END
     augroup! airline
 
     if exists("s:stl")
-      let &stl = s:stl
+      let &statusline = s:stl
     endif
     if exists("s:tal")
-      let [&tal, &showtabline] = s:tal
+      let [&tabline, &showtabline] = s:tal
     endif
     call airline#highlighter#reset_hlcache()
-
     call airline#util#doautocmd('AirlineToggledOff')
   else
     let s:stl = &statusline
@@ -147,65 +148,72 @@ function! s:airline_toggle()
       autocmd ColorScheme * call <sid>on_colorscheme_changed()
       " Set all statuslines to inactive
       autocmd FocusLost * call airline#update_statusline_focuslost()
+      
       " Refresh airline for :syntax off
       autocmd SourcePre */syntax/syntax.vim
             \ call airline#extensions#tabline#buffers#invalidate()
+            
       autocmd VimEnter * call <sid>on_window_changed('VimEnter')
       autocmd WinEnter * call <sid>on_window_changed('WinEnter')
       autocmd FileType * call <sid>on_window_changed('FileType')
       autocmd BufWinEnter * call <sid>on_window_changed('BufWinEnter')
       autocmd BufUnload * call <sid>on_window_changed('BufUnload')
+      
       if exists('##CompleteDone')
         autocmd CompleteDone * call <sid>on_window_changed('CompleteDone')
       endif
+      
       " non-trivial number of external plugins use eventignore=all, so we need to account for that
       autocmd CursorMoved * call <sid>on_cursor_moved()
-
       autocmd VimResized * call <sid>on_focus_gained()
+
       if exists('*timer_start') && exists('*funcref') && &eventignore !~? 'focusgained'
         " do not trigger FocusGained on startup, it might erase the intro screen (see #1817)
         " needs funcref() (needs 7.4.2137) and timers (7.4.1578)
         let Handler = funcref('<sid>FocusGainedHandler')
         let s:timer = timer_start(5000, Handler)
       else
-        autocmd FocusGained * call <sid>on_focus_gained()
+        autocmd FocusGained * call s:on_focus_gained()
       endif
 
       if exists("##TerminalOpen")
         " Using the same function with the TermOpen autocommand
         " breaks for Neovim see #1828, looks like a neovim bug.
-        autocmd TerminalOpen * :call airline#load_theme() " reload current theme for Terminal, forces the terminal extension to be loaded
+        autocmd TerminalOpen * call airline#load_theme()
       endif
-      autocmd TabEnter * :unlet! w:airline_lastmode | let w:airline_active=1
+      
+      autocmd TabEnter * unlet! w:airline_lastmode | let w:airline_active = 1
+      
       autocmd BufWritePost */autoload/airline/themes/*.vim
-            \ exec 'source '.split(globpath(&rtp, 'autoload/airline/themes/'.g:airline_theme.'.vim', 1), "\n")[0]
+            \ execute 'source '.split(globpath(&rtp, 'autoload/airline/themes/'.g:airline_theme.'.vim', 1), "\n")[0]
             \ | call airline#load_theme()
+            
       autocmd User AirlineModeChanged nested call airline#mode_changed()
 
       if get(g:, 'airline_statusline_ontop', 0)
         " Force update of tabline more often
-        autocmd InsertEnter,InsertLeave,CursorMovedI * :call airline#update_tabline()
+        autocmd InsertEnter,InsertLeave,CursorMovedI * call airline#update_tabline()
       endif
 
       if exists("##ModeChanged")
-        autocmd ModeChanged * :call airline#update_tabline()
+        autocmd ModeChanged * call airline#update_tabline()
       endif
     augroup END
 
     if !airline#util#stl_disabled(winnr())
       if &laststatus < 2
-        let _scroll=&scroll
+        let scroll_bak = &scroll
         if !get(g:, 'airline_statusline_ontop', 0)
           set laststatus=2
         endif
-        if &scroll != _scroll
+        let &scroll = scroll_bak
-          let &scroll = _scroll
       endif
     endif
-    endif
+
-    if airline#util#has_multiline() && &statuslineopt !~ 'maxheight:'
+    if airline#util#has_multiline() && &statuslineopt !~# 'maxheight:'
       set statuslineopt+=maxheight:2
     endif
+
     if s:airline_initialized
       call s:on_window_changed('Init')
     endif
@@ -226,7 +234,7 @@ function! s:airline_theme(...)
         let theme = s:random_theme()
       endif
       call airline#switch_theme(theme)
-    catch " discard error
+    catch
     endtry
     if a:1 is# 'random'
       echo g:airline_theme
@@ -255,10 +263,10 @@ endfunction
 function! s:FocusGainedHandler(timer)
   if exists("s:timer") && a:timer == s:timer && exists('#airline') && &eventignore !~? 'focusgained'
     augroup airline
-      au FocusGained * call s:on_focus_gained()
+      autocmd FocusGained * call s:on_focus_gained()
     augroup END
   endif
-endfu
+endfunction
 
 function! s:airline_extensions()
   let loaded = airline#extensions#get_loaded_extensions()
@@ -299,13 +307,10 @@ function! s:rand(max) abort
   elseif has("reltime")
     let timerstr = reltimestr(reltime())
     let number = split(timerstr, '\.')[1] + 0
-  elseif has("win32") && &shell =~ 'cmd'
+  elseif has("win32") && &shell =~? 'cmd'
     let number = system("echo %random%") + 0
   else
     " best effort, bash and zsh provide $RANDOM
-    " cmd.exe on windows provides %random%, but expand()
-    " does not seem to be able to expand this correctly.
-    " In the worst case, this always returns zero
     let number = expand("$RANDOM") + 0
   endif
   return number % a:max
@@ -324,6 +329,7 @@ command! AirlineExtensions   call s:airline_extensions()
 
 call airline#init#bootstrap()
 call s:airline_toggle()
+
 if exists("v:vim_did_enter") && v:vim_did_enter
   call <sid>on_window_changed('VimEnter')
 endif