Optional plugins

[horseinthesky]

Hello.
I've just started the transition from VIM script to lua and decided to start with plugin manage. The first two questions come to mind:

1. As fas as I understood there are optional plugins and start plugins. But I could find the difference between them. Why should I install packer as opt plugin? Or in general, should I? The same is about start plugins.
2. I have some install options in VIm Plug:

Plug 'junegunn/fzf', { 'dir': '~/.fzf', 'do': './install --all' }
Plug 'junegunn/fzf.vim'
Plug 'kkoomen/vim-doge', { 'do': { -> doge#install() } }

How can I achieve the same in packer?
3) While doing the transition I want to my lua setup be loaded only for NVIM 0.5 so I added this to my init.vim

if has('nvim-0.5')
  :lua require'setup'
endif                

and then in my setup.lua I have

local fn = vim.fn
local execute = vim.api.nvim_command

-- Sensible defaults
require('settings')

-- Auto install packer.nvim if not exists
local install_path = fn.stdpath('data')..'/site/pack/packer/opt/packer.nvim'
if fn.empty(fn.glob(install_path)) > 0 then
  execute('!git clone https://github.com/wbthomason/packer.nvim '..install_path)
end
vim.cmd [[packadd packer.nvim]]
vim.cmd 'autocmd BufWritePost plugins.lua PackerCompile' -- Auto compile when there are changes in plugins.lua

-- Install plugins
require('plugins')

-- Setup Lua language server using submodule
require('lsp')

But whathever NVIM 0.4.3 or 0.5 I run it always loads packer (which in turn loads lsp etc.)

Invalid Neovim version for packer.nvim!
Error detected while processing /home/horseinthesky/.local/share/nvim/site/pack/packer/start/nvim-lspconfig/plugin/ls
pconfig.vim:
line   11:
E5105: Error while calling lua chunk: .../pack/packer/start/nvim-lspconfig/lua/lspconfig/util.lua:11: attempt to inde
x local 'lsp' (a nil value)

Is there a way to achieve what I want - packer only for NVIM 0.5?

Thank you.

[wbthomason]

But I could find the difference between them. Why should I install packer as opt plugin? Or in general, should I? The same is about start plugins.

If you haven't read :help packages, I'd suggest starting there. The short version is that start plugins are eagerly loaded, whereas opt plugins must be loaded with packadd. A large part of packer's job is handling the latter for you. In general, default to start, and use opt when you have some reason to lazy-load a plugin (e.g. it's only relevant for some filetypes, or imposes a high startup cost, etc.)

How can I achieve the same in packer?

The equivalent is packer's run key: https://github.com/wbthomason/packer.nvim#updateinstall-hooks

Is there a way to achieve what I want - packer only for NVIM 0.5?

Hmm, not super easily. The problem is that start packages always get eagerly loaded, so you'd need to uninstall them between version switches. You could maybe do some trickery with setting packpath differently based on whether you're in 0.5 or not, but I haven't tried this myself and am not sure if it would work.

I hope this helps!

[horseinthesky]

Thank you.
I've opened #237 and @nanotee and @akinsho helped me to find a more or less simple way to achieve what I wanted:

1. To use a custom path for packer_compiled.vim
2. To use a simple cond to make plugins optional but still have lazy-loading for them.

There are two more related issues though I cannot figure out how to handle
#244
#245

Could you pls take a look at them?

[wbthomason]

Yep, I'm getting there. Sorry for the delay; I had to take a while fully away from packer for real work, so I'm working through the backlog of issues now.

[horseinthesky]

There is no hurry. I'm just investigating Lua's possibilities for my NVIM environment.
And want to say thank you help and such an interesting plugin manager =)