project-based config: how to load plugins/colors from custom subdir of $PWD when doing `vim -u local/vimrc ...`?

Question

The Need, the Goal...

By "project-based config" I mean a project contained in a git repo that contains all the vim configuration -- vimrc and plugins and colorschemes -- right there in the repo. In my case this is in the repo's .config directory.

So: cd path/to/project && vi -u .config/vimrc some-script.py should... somehow ...load all the plugins/colorschemes contained in that .config directory, ignoring the standard ~/.vimrc and ~/.vim/* config files.

Possible Strategies

1. Plugin manager:
   • vundle
   • pathogen
   • vim-plug
2. a plugin made for this
   • like https://github.com/LucHermitte/local_vimrc as a possibility
3. manual configuration
   • perhaps has multiple ways it could be achieved?
4. magic:
   • vim considers ~/.vimrc and ~/.vim/ to always be siblings so if you do vi -u path/to/config/vimrc since vim is smart it will automatically look for plugins inside path/to/config/vim
5. something else?

Problems

Well...

• #4 doesn't seem to exist.
• #2 doesn't match my criteria, as "an automatic way of sourcing vimrc from current directory" is a different use-case, I don't want automatic, it should require explicit intention by invoking -u or something comparable.
• #1: I've used pathogen for years, but I'm not sure if it's even capable of this. I tried using vim-plug and could get that working in the same way pathogen works (with standard location of config files) but couldn't get it working for this use case.
• #3 I've spent hours reading :h packages, :h packpath, :h runtimepath, and trying to derive a solution from them but nothing yet works. The trouble here is that :h packages is not clear about the distinction between foo and foobar in the context of a plugin that we find off Github (it describes unzipping individually zipped files). Not a single plugin has I've seen has a start or opt directory, but it says to manually create that, though it's not explicitly clear about "where"... so just guess, and try every option! I did this to no avail. Additionally, :h packpath is not helpful and :h packages has no mention of it... but these two things might need to be used in tandem(?).

Answer 1

There are two related options: packpath and runtimepath.

If you set packpath then all plugins sub-trees must reside under pack/<bundle>/{start,opt} to comply with :h packages.

If you set runtimepath directly then you must add every separate plugin subtree to runtimepath (and then also runtime! plugin/**/*.vim manually in case you have any). Also, you'll probably want to have --noplugin or set noloadplugins to disable auto expansion.

And last but not least, use valid VimScript only: only some commands accept arbitrary expressions. set is not one of them (consider that we write set xyz=foobar and NOT set xyz="foobar").

Answer 2

For a manual method, packpath can provide a solution (using only a single line of code in the vimrc file) with the following constraints:

set packpath=.config/vim will allow you to put plugins inside .config/vim/pack/*/start/ (as well as .config/vim/pack/*/opt/) and this will work when invoked like vi -u .config/vimrc scriptname.py.

But when in a subdirectory of the project that packpath value won't work; if you're doing vi -u ../.config/vimrc data.json then the plugins will not load. So you either need to:

• know the full path and hardcode the location like set packpath=~/path/to/project/.config/vim
• write some vimscript/etc to trace through parent directories to somehow identify the location (based on your project's unique structure) of the vim config, and then do executure ':set packpath=' . yourVariable since set can't take variables on its own.
• or, if you can accept this limitation, just always invoke vim from that project root

Once you've done set packpath in your project-specific vimrc, then you can add as many plugins you'd like...

:h packages says

"When Vim starts up, after processing your .vimrc, it scans all directories in packpath for plugins under the "pack/*/start" directory."

So if packpath=~/path/to/project/.config/vim then you can:

• place plugins inside one big ...pack/bundle/start directory like:
  • ~/path/to/project/.config/vim/pack/all-plugins/start/plugin-1-dir
  • ~/path/to/project/.config/vim/pack/all-plugins/start/plugin-2-dir
  • ~/path/to/project/.config/vim/pack/all-plugins/start/plugin-3-dir
• or you can be more specific and do:
  • ~/path/to/project/.config/vim/pack/plugin1/start/plugin-1-dir
  • ~/path/to/project/.config/vim/pack/plugin2/start/plugin-2-dir
  • ~/path/to/project/.config/vim/pack/plugin3/start/plugin-3-dir
• and if you don't want the plugin loaded right when Vim starts then you can use opt directory instead of start like ...pack/anything/opt/plugin-4-dir.

plugin-1-dir, plugin-2-dir etc is just the name of the plugin from when you git clone it (or however you get it), and the file/directory structure that the module comes with can be used as-is without modification.