Update a Vim Session file's loaded plugins without losing window positioning

Question

I have a Vim Session file I created by doing:

:mksession

Then I quit Vim. I then downloaded a plugin to:

${HOME}/.vim/pack/vendor/start/vim-markdown-folding

and then I fired up Vim with the session file by doing

vim -S Session.vim

Then I attempted to open the help docs for the vim-markdown-folding plugin by doing:

:helptags ALL
:help markdown-folding

Which Vim told me that it didn't exist. So I opened a new terminal tab, and tried it in a different vim session without loading the Session file. The help command worked. So I tried then to :source $MYVIMRC in the Vim that loaded the Session.vim and it still didn't update the loaded plugins. The only other way I can think of to do this is to delete the Session.vim file and reposition all my open splits and windows, which I DO NOT want to do.

How do I make Vim update the Session.vim file and the list of plugins that should be loaded when editing certain files without deleting the existing Session.vim and losing all those settings?

Why would the Session.vim file detail the plugins loaded or not update them when I tell it to :packadd or to :mksession! again or reload my $MYVIMRC?

Comment Chat is here

Answer 1

With the help of @Matt, we were able to get my new plugins loaded, and markdown folds working.

1. Open vim with the session file

   vim -S Session.vim

2. Modify sessionoptions by removing options and folds from the sesion options

-- :set sessionoptions=blank,buffers,curdir,folds,help,options,tabpages,winsize,terminal
++ :set sessionoptions=blank,buffers,curdir,help,tabpages,winsize,terminal

3. Save the session

   :mksession

4. Quit and restart Vim with the session file again.

   • This should load up all the new plugins that were added after the initial plugins were saved in the session file. This will also allow any folding plugins to perform their function.

5. With all the new plugins loaded, folds set, check the sessionoptions again. It should have the original options set.

6. Save the session again.

   :mksession!

7. Quit and start Vim again with the Session file.

This should have all the relevant packages loaded, folds set, and windows in their position. To help make this easier and quicker to run the following

vim -S Session.vim \
    -c "set sessionoptions=blank,buffers,curdir,help,tabpages,winsize,terminal" \
    -c "mksession!" \
    -c "q"

vim -S Session.vim \
    -c "mksession!" \
    -c "q"