my-nvim-setup/lua/core/lazy_load.lua

local M = {}
local autocmd = vim.api.nvim_create_autocmd

-- require("packer").loader(tb.plugins)
-- This must be used for plugins that need to be loaded just after a file
-- ex : treesitter, lspconfig etc
M.lazy_load = function(tb)
  autocmd(tb.events, {
    group = vim.api.nvim_create_augroup(tb.augroup_name, {}),
    callback = function()
      if tb.condition() then
        vim.api.nvim_del_augroup_by_name(tb.augroup_name)

        -- dont defer for treesitter as it will show slow highlighting
        -- This deferring only happens only when we do "nvim filename"
        if tb.plugin ~= "nvim-treesitter" then
          vim.defer_fn(function()
            require("packer").loader(tb.plugin)
            if tb.plugin == "nvim-lspconfig" then
              vim.cmd "silent! e %"
            end
          end, 0)
        else
          require("packer").loader(tb.plugin)
        end
      end
    end,
  })
end

-- load certain plugins only when there's a file opened in the buffer
-- if "nvim filename" is executed -> load the plugin after nvim gui loads
-- This gives an instant preview of nvim with the file opened

M.on_file_open = function(plugin_name)
  M.lazy_load {
    events = { "BufRead", "BufWinEnter", "BufNewFile" },
    augroup_name = "BeLazyOnFileOpen" .. plugin_name,
    plugin = plugin_name,
    condition = function()
      local file = vim.fn.expand "%"
      return file ~= "NvimTree_1" and file ~= "[packer]" and file ~= ""
    end,
  }
end

M.treesitter_cmds = {
  "TSInstall",
  "TSBufEnable",
  "TSBufDisable",
  "TSEnable",
  "TSDisable",
  "TSModuleInfo",
}

M.mason_cmds = {
  "Mason",
  "MasonInstall",
  "MasonInstallAll",
  "MasonUninstall",
  "MasonUninstallAll",
  "MasonLog",
}

M.gitsigns = function()
  -- taken from https://github.com/max397574
  autocmd({ "BufRead" }, {
    callback = function()
      local function onexit(code, _)
        if code == 0 then
          vim.schedule(function()
            require("packer").loader "gitsigns.nvim"
          end)
        end
      end
      local lines = vim.api.nvim_buf_get_lines(0, 0, -1, false)
      if lines ~= { "" } then
        vim.loop.spawn("git", {
          args = {
            "ls-files",
            "--error-unmatch",
            vim.fn.expand "%:p:h",
          },
        }, onexit)
      end
    end,
  })
end

return M