Vim, NERDtree not recovered in session restore

Question

When I have a NERDtree panel and I save a Vim session (mksession [filename]), then open the session (vim -S filename), the panel is opened and tagged \"NERDtree\" but is not pop

Answer 1

Another solution based on stevelove's:

fun! Mksession(name)
    let need_tree = g:NERDTree.IsOpen()
    NERDTreeClose
    execute "mksession! " . a:name
    if need_tree
        call writefile(readfile(a:name)+['NERDTree'], a:name)
        NERDTree
    endif
endfun

command! -nargs=1 Mksession call Mksession()