feat: register individual plugin specs for lazy loading

by passing a single spec to `load()`

lua/lz/n/init.lua

@@ -16,26 +16,40 @@ end)
 
 ---@param spec string | lz.n.Spec
 function M.load(spec)
-    if vim.g.lz_n_did_load then
-        return vim.notify("lz.n has already loaded your plugins.", vim.log.levels.WARN, { title = "lz.n" })
-    end
-    vim.g.lz_n_did_load = true
-
     if type(spec) == "string" then
         spec = { import = spec }
     end
-    ---@cast spec lz.n.Spec
-    local plugins = require("lz.n.spec").parse(spec)
+    --- @cast spec lz.n.Spec
+    local spec_mod = require("lz.n.spec")
+    local is_single_plugin_spec = spec_mod.is_single_plugin_spec(spec)
+    if not is_single_plugin_spec then
+        if vim.g.lz_n_did_load then
+            return vim.notify(
+                "lz.n.load() should only be called on a list of plugin specs once.",
+                vim.log.levels.WARN,
+                { title = "lz.n" }
+            )
+        end
+        vim.g.lz_n_did_load = true
+    end
+    local plugins = spec_mod.parse(spec)
     require("lz.n.loader").load_startup_plugins(plugins)
-    require("lz.n.state").plugins = plugins
+
+    local state = require("lz.n.state")
+    if is_single_plugin_spec then
+        state.plugins = vim.tbl_deep_extend("force", state.plugins, plugins)
+    else
+        state.plugins = plugins
+    end
     require("lz.n.handler").init(plugins)
     if vim.v.vim_did_enter == 1 then
         deferred_ui_enter()
-    else
+    elseif not vim.g.lz_n_did_create_deferred_ui_enter_autocmd then
         vim.api.nvim_create_autocmd("UIEnter", {
             once = true,
             callback = deferred_ui_enter,
         })
+        vim.g.lz_n_did_create_deferred_ui_enter_autocmd = true
     end
 end
 

lua/lz/n/loader.lua

@@ -16,7 +16,7 @@ function M._load(plugin)
     end
     require("lz.n.handler").disable(plugin)
     ---@type fun(name: string) | nil
-    local load_impl = vim.tbl_get(vim.g, "lz_n", "load")
+    local load_impl = plugin.load or vim.tbl_get(vim.g, "lz_n", "load")
     if type(load_impl) == "function" then
         load_impl(plugin.name)
     else

lua/lz/n/meta.lua

@@ -9,6 +9,10 @@ error("Cannot import a meta module")
 --- Only useful for lazy=false plugins to force loading certain plugins first.
 --- Default priority is 50
 --- @field priority? number
+---
+--- Set this to override the `load` function for an individual plugin.
+--- Defaults to `vim.g.lz_n.load()`, see |lz.n.Config|.
+--- @field load? fun(name: string)
 
 --- @alias lz.n.Event {id:string, event:string[]|string, pattern?:string[]|string}
 --- @alias lz.n.EventSpec string|{event?:string|string[], pattern?:string|string[]}|string[]

lua/lz/n/spec.lua

@@ -123,16 +123,28 @@ local function parse(spec)
     return result
 end
 
+---@param spec lz.n.Spec
+---@return boolean
+function M.is_spec_list(spec)
+    return #spec > 1 or vim.islist(spec) and #spec > 1
+end
+
+---@param spec lz.n.Spec
+---@return boolean
+function M.is_single_plugin_spec(spec)
+    return type(spec[1]) == "string"
+end
+
 ---@private
 ---@param spec lz.n.Spec
 ---@param result table<string, lz.n.Plugin>
 function M._normalize(spec, result)
-    if #spec > 1 or vim.islist(spec) and #spec > 1 then
+    if M.is_spec_list(spec) then
         ---@cast spec lz.n.Spec[]
         for _, sp in ipairs(spec) do
             M._normalize(sp, result)
         end
-    elseif spec[1] then
+    elseif M.is_single_plugin_spec(spec) then
         ---@cast spec lz.n.PluginSpec
         result[spec[1]] = parse(spec)
     elseif spec.import then