Add option to not trigger update on large files

autoload/tagbar.vim

@@ -1158,6 +1158,20 @@ function! s:ProcessFile(fname, ftype) abort
         return
     endif
 
+    " If the file size limit it set, then check the linecount to see if
+    " this file should be ignored or not.
+    if g:tagbar_file_size_limit > 0
+        let linecount = line('$')
+        if linecount > g:tagbar_file_size_limit && !exists('b:tagbar_force_update')
+            call tagbar#debug#log('[ProcessFile] File size too large (' . linecount . ' lines) - limit set to ' . g:tagbar_file_size_limit)
+            if !exists('b:tagbar_file_exceeds_limit')
+                echom 'File size too large (' . linecount . ' lines) - Not processing file (see help for g:tagbar_file_size_limit).'
+                let b:tagbar_file_exceeds_limit = 1
+            endif
+            return
+        endif
+    endif
+
     let typeinfo = s:known_types[a:ftype]
 
     " If the file has only been updated preserve the fold states, otherwise
@@ -3578,6 +3592,16 @@ function! tagbar#Update() abort
     call s:AutoUpdate(fnamemodify(expand('%'), ':p'), 0)
 endfunction
 
+"  tagbar#ForceUpdate() {{{2
+function! tagbar#ForceUpdate() abort
+    if !exists('b:tagbar_force_update')
+        let b:tagbar_force_update = 1
+        call s:AutoUpdate(fnamemodify(expand('%'), ':p'), 1)
+        unlet b:tagbar_force_update
+        unlet b:tagbar_file_exceeds_limit
+    endif
+endfunction
+
 " tagbar#toggle_pause() {{{2
 function! tagbar#toggle_pause() abort
     let s:paused = !s:paused

doc/tagbar.txt

@@ -337,6 +337,10 @@ FUNCTIONS                                                   *tagbar-functions*
         return tag . ' --- ' . lines . ' lines'
     endfunction
 <
+*tagbar#ForceUpdate()*
+    Forcefully update a file even if it exceeds the |g:tagbar_file_size_limit|
+    value. This also clears the internal flags to the file will be re-examined
+    again.
 
 ------------------------------------------------------------------------------
 KEY MAPPINGS                                                     *tagbar-keys*
@@ -882,6 +886,21 @@ Example:
 >
         let g:tagbar_use_cache = 0
 <
+                                                     *g:tagbar_file_size_limit*
+g:tagbar_file_size_limit~
+Default: 0
+
+By default, all files are processed by tagbar. Setting this value to non-zero
+will disable processing for any file with a line count greater than
+|g:tagbar_file_size_limit|. A message will be displayed once for a given buffer
+if the limit is exceeded. The file can be forcefully updated with the
+|tagbar#ForceUpdate()| function. If the value is set to 0, then the file will
+always be processed.
+
+Example:
+>
+    let g:tagbar_file_size_limit = 10000
+<
 
 ------------------------------------------------------------------------------
 HIGHLIGHT COLOURS                                           *tagbar-highlight*

plugin/tagbar.vim

@@ -91,6 +91,7 @@ function! s:setup_options() abort
         \ ['case_insensitive', 0],
         \ ['compact', 0],
         \ ['expand', 0],
+        \ ['file_size_limit', 0],
         \ ['foldlevel', 99],
         \ ['hide_nonpublic', 0],
         \ ['height', 10],