Cache files locally for parsing

Files are now cached locally in a temporary file, and the parsing
happens on that file. This allows displaying tags for remote (Netrw)
files, and it will also make access to files on remote filesystems like
NFS and sshfs faster.

Additionally, tags are now always updated when the files are saved,
deprecating the tagbar_updateonsave_maxlines option. Otherwise checking
for changes in remote files would not have been possible.

autoload/tagbar.vim

@@ -890,7 +890,7 @@ function! s:RestoreSession() abort
 
     call s:InitWindow(g:tagbar_autoclose)
 
-    call s:AutoUpdate(curfile)
+    call s:AutoUpdate(curfile, 0)
 
     if !in_tagbar
         call s:winexec('wincmd p')
@@ -951,12 +951,10 @@ function! s:CreateAutocommands() abort
         autocmd BufEnter   __Tagbar__ nested call s:QuitIfOnlyWindow()
         autocmd CursorHold __Tagbar__ call s:ShowPrototype()
 
-        autocmd BufWritePost *
-            \ if line('$') < g:tagbar_updateonsave_maxlines |
-                \ call s:AutoUpdate(fnamemodify(expand('<afile>'), ':p')) |
-            \ endif
+        autocmd BufWritePost * call
+                    \ s:AutoUpdate(fnamemodify(expand('<afile>'), ':p'), 1)
         autocmd BufEnter,CursorHold,FileType * call
-                    \ s:AutoUpdate(fnamemodify(expand('<afile>'), ':p'))
+                    \ s:AutoUpdate(fnamemodify(expand('<afile>'), ':p'), 0)
         autocmd BufDelete,BufUnload,BufWipeout * call
                     \ s:known_files.rm(fnamemodify(expand('<afile>'), ':p'))
 
@@ -1431,6 +1429,8 @@ function! s:FileInfo.New(fname, ftype) abort dict
     " The complete file path
     let newobj.fpath = a:fname
 
+    let newobj.bufnr = bufnr(a:fname)
+
     " File modification time
     let newobj.mtime = getftime(a:fname)
 
@@ -1629,7 +1629,7 @@ function! s:OpenWindow(flags) abort
 
     call s:InitWindow(autoclose)
 
-    call s:AutoUpdate(curfile)
+    call s:AutoUpdate(curfile, 0)
     call s:HighlightTag(1, curline)
 
     if !(g:tagbar_autoclose || autofocus || g:tagbar_autofocus)
@@ -1809,22 +1809,6 @@ function! s:ProcessFile(fname, ftype) abort
         return
     endif
 
-    let ctags_output = s:ExecuteCtagsOnFile(a:fname, a:ftype)
-
-    if ctags_output == -1
-        call s:LogDebugMessage('Ctags error when processing file')
-        " put an empty entry into known_files so the error message is only
-        " shown once
-        call s:known_files.put({}, a:fname)
-        return
-    elseif ctags_output == ''
-        call s:LogDebugMessage('Ctags output empty')
-        " No need to go through the tag processing if there are no tags, and
-        " preserving the old fold state also isn't necessary
-        call s:known_files.put(s:FileInfo.New(a:fname, a:ftype), a:fname)
-        return
-    endif
-
     " If the file has only been updated preserve the fold states, otherwise
     " create a new entry
     if s:known_files.has(a:fname)
@@ -1834,6 +1818,29 @@ function! s:ProcessFile(fname, ftype) abort
         let fileinfo = s:FileInfo.New(a:fname, a:ftype)
     endif
 
+    let tempfile = tempname()
+
+    call writefile(getbufline(fileinfo.bufnr, 1, '$'), tempfile)
+    let fileinfo.mtime = getftime(tempfile)
+
+    let ctags_output = s:ExecuteCtagsOnFile(tempfile, a:ftype)
+
+    call delete(tempfile)
+
+    if ctags_output == -1
+        call s:LogDebugMessage('Ctags error when processing file')
+        " Put an empty entry into known_files so the error message is only
+        " shown once
+        call s:known_files.put({}, a:fname)
+        return
+    elseif ctags_output == ''
+        call s:LogDebugMessage('Ctags output empty')
+        " No need to go through the tag processing if there are no tags, and
+        " preserving the old fold state isn't necessary either
+        call s:known_files.put(s:FileInfo.New(a:fname, a:ftype), a:fname)
+        return
+    endif
+
     let typeinfo = fileinfo.typeinfo
 
     " Parse the ctags output lines
@@ -2948,7 +2955,7 @@ endfunction
 
 " Helper functions {{{1
 " s:AutoUpdate() {{{2
-function! s:AutoUpdate(fname) abort
+function! s:AutoUpdate(fname, force) abort
     call s:LogDebugMessage('AutoUpdate called on ' . a:fname)
 
     " Get the filetype of the file we're about to process
@@ -2974,14 +2981,22 @@ function! s:AutoUpdate(fname) abort
 
     let updated = 0
 
-    " Process the file if it's unknown or the information is outdated
+    " Process the file if it's unknown or the information is outdated.
     " Also test for entries that exist but are empty, which will be the case
-    " if there was an error during the ctags execution
+    " if there was an error during the ctags execution.
+    " Testing the mtime of the file is necessary in case it got changed
+    " outside of Vim, for example by checking out a different version from a
+    " VCS.
     if s:known_files.has(a:fname) && !empty(s:known_files.get(a:fname))
-        if s:known_files.get(a:fname).mtime != getftime(a:fname)
+        let curfile = s:known_files.get(a:fname)
+        " if a:force || getbufvar(curfile.bufnr, '&modified') ||
+        if a:force ||
+         \ (filereadable(a:fname) && getftime(a:fname) > curfile.mtime)
             call s:LogDebugMessage('File data outdated, updating ' . a:fname)
             call s:ProcessFile(a:fname, sftype)
             let updated = 1
+        else
+            call s:LogDebugMessage('File data seems up to date: ' . a:fname)
         endif
     elseif !s:known_files.has(a:fname)
         call s:LogDebugMessage('New file, processing ' . a:fname)
@@ -3006,7 +3021,7 @@ function! s:AutoUpdate(fname) abort
     endif
 
     " Call setCurrent after rendering so RenderContent can check whether the
-    " same file is redisplayed
+    " same file is being redisplayed
     if !empty(fileinfo)
         call s:LogDebugMessage('Setting current file to ' . a:fname)
         call s:known_files.setCurrent(fileinfo)
@@ -3219,7 +3234,7 @@ function! s:IsValidFile(fname, ftype) abort
         return 0
     endif
 
-    if !filereadable(a:fname)
+    if !filereadable(a:fname) && getbufvar(a:fname, 'netrw_tmpfile') == ''
         call s:LogDebugMessage('File not readable')
         return 0
     endif

doc/tagbar.txt

@@ -473,19 +473,9 @@ Example:
 
                                               *g:tagbar_updateonsave_maxlines*
 g:tagbar_updateonsave_maxlines~
-Default: 5000
 
-If the current file has fewer lines than the value of this variable, Tagbar
-will update immediately after saving the file. If it is longer then the update
-will only happen on the |CursorHold| event and when switching buffers (or
-windows). This is to prevent the time it takes to save a large file from
-becoming annoying in case you have a slow computer. If you have a fast
-computer you can set it to a higher value.
+Deprecated. Tagbar will now always get updated when the file is being saved.
 
-Example:
->
-        let g:tagbar_updateonsave_maxlines = 10000
-<
 
                                                           *g:tagbar_systemenc*
 g:tagbar_systemenc~

plugin/tagbar.vim

@@ -91,10 +91,6 @@ if !exists('g:tagbar_autoshowtag')
     let g:tagbar_autoshowtag = 0
 endif
 
-if !exists('g:tagbar_updateonsave_maxlines')
-    let g:tagbar_updateonsave_maxlines = 5000
-endif
-
 if !exists('g:tagbar_systemenc')
     let g:tagbar_systemenc = &encoding
 endif