Problem on generating GRTAGS for vim scripts

[John Rama]

Hi,

I keep using global/gtags for reading c/python/javascripts and it
works greatly. Thank you for that !!                                         
                                                                     
But when trying to create tags files for vim script,                 
GTAGS files are generated correctly, but GRTAGS files are not        
complete.                                                            
                                                                     
- Environement                                                       
    $gtags --version                                                   
    gtags (GNU GLOBAL) 6.6                                             
    $python3 -m pip list |grep Pygments                                
    Pygments   2.9.0                                                   
                                                                     
- How to duplicate the problem                                       
    $git clone  https://github.com/itchyny/lightline.vim               
    $gtags --gtagslabel=pygments -v                                    
                                                                       
- Problem                                                            
    For example, symbol for lightline#highlight() is generated in GTAGS
    file, but it's not in GRTAGS.                                      
    So, it looks lightline#highlight symbol becomes "highlight".       
                                                                     
    $gtags -d GTAGS |grep high                                         
    lightline#highlight     42 @n 263 function! @n(...) abort          
    s:suite 51 @n 1 let @n = themis#suite('highlight')                 
    suite.highlight 51 @n 21 function! s:@n()                          
                                                                     
    $gtags -d GRTAGS |grep high                                        
    highlight       51 @n 21,19,17,16                                  
    highlight       42 @n 54,2,146-1,21-1,38,7,40-1,121-1              
    highlight       3 @n 22,2
                                          
- Questions                                                                     
Is this expected behavior ?                                          
Is there any workaround on this ?                         

Thanks for your help.
John