fix: handle more lazy loading issues

## Details

Related issues:

- #309
- #315
- #317

Okay this is getting convoluted to handle the differences in lazy
loading between `lazy.nvim` and `vim-plug`. The issues are as follows:

- `lazy.nvim` & Lazy Loaded: Attempting to attach to current buffer at
  the start will not pickup user configuration (called from plugin
  directory before setup) so may not listen to all needed events. This
  means we should not attach to current buffer and rely on the
  `FileType` auto command.
- `vim-plug` & Lazy Loaded: The initial load swallows the `FileType`
  event for the current buffer (`lazy.nvim` seems to trigger the event)
  so first buffer will be ignored. This means we cannot rely on the
  `FileType` auto command and need to attach to the current buffer.

To fix this we need to be aware of the plugin manager being used so we
can do the right thing, which sucks, but oh well.

The solution expands on our existing logic to hook into `lazy.nvim`
configuration for this plugin. When the user has NOT configured lazy
loading (via filetypes nor commands) we attempt to attach to the current
buffer. This means if they have we will skip attaching and will rely on
the `FileType` event.

This solves the `lazy.nvim` problem of not using the updated user
configuration. This does mean when not lazy loading with `lazy.nvim` we
will attempt to attach to the current buffer. This will initially fail
since the filetype will not be set for the buffer but will succeed for
the buffer later once the `FileType` event is triggered.

For `vim-plug` we don't have any hooks so no matter what it will look
like we are NOT lazy loading. This means we will attempt to attach to
the current buffer fixing the issue of lazy loading with `vim-plug`.

Have also added a check that buffer is valid in the `should_attach`
function. The issue related to this should be fixed from the other
updates but having it in place seems like a good idea in either case.

Author: MeanderingProgrammer

doc/render-markdown.txt

@@ -1,4 +1,4 @@
-*render-markdown.txt*          For 0.10.0         Last change: 2025 January 31
+*render-markdown.txt*         For 0.10.0         Last change: 2025 February 01
 
 ==============================================================================
 Table of Contents                          *render-markdown-table-of-contents*

lua/render-markdown/core/util.lua

@@ -3,9 +3,9 @@ local M = {}
 
 M.has_10 = vim.fn.has('nvim-0.10') == 1
 
----@param name string
+---@param key 'ft'|'cmd'
 ---@return string[]
-function M.lazy_file_types(name)
+function M.lazy(key)
     -- https://github.com/folke/lazydev.nvim/blob/main/lua/lazydev/pkg.lua -> get_plugin_path
     if type(package.loaded.lazy) ~= 'table' then
         return {}
@@ -14,15 +14,16 @@ function M.lazy_file_types(name)
     if not ok then
         return {}
     end
+    local name = 'render-markdown.nvim'
     local plugin = lazy_config.spec.plugins[name]
     if plugin == nil then
         return {}
     end
-    local file_types = plugin.ft
-    if type(file_types) == 'table' then
-        return file_types
-    elseif type(file_types) == 'string' then
-        return { file_types }
+    local values = plugin[key]
+    if type(values) == 'table' then
+        return values
+    elseif type(values) == 'string' then
+        return { values }
     else
         return {}
     end

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '7.8.13'
+M.version = '7.8.14'
 
 function M.check()
     M.start('version')

lua/render-markdown/manager.lua

@@ -15,7 +15,9 @@ M.group = vim.api.nvim_create_augroup('RenderMarkdown', { clear = true })
 ---Should only be called from plugin directory
 function M.setup()
     -- Lazy Loading: ignores current buffer as FileType event already executed
-    M.schedule_attach()
+    if #util.lazy('ft') == 0 and #util.lazy('cmd') == 0 then
+        M.attach_current()
+    end
     -- Attempt to attach to all buffers, cannot use pattern to support plugin directory
     vim.api.nvim_create_autocmd('FileType', {
         group = M.group,
@@ -43,7 +45,9 @@ end
 ---@param enabled boolean
 function M.set_all(enabled)
     -- Lazy Loading: all previously opened buffers have been ignored
-    M.schedule_attach()
+    if #util.lazy('cmd') > 0 then
+        M.attach_current()
+    end
     state.enabled = enabled
     for _, buf in ipairs(buffers) do
         ui.update(buf, vim.fn.bufwinid(buf), 'UserCommand', true)
@@ -57,11 +61,8 @@ function M.is_attached(buf)
 end
 
 ---@private
-function M.schedule_attach()
-    local buf = util.current('buf')
-    vim.schedule(function()
-        M.attach(buf)
-    end)
+function M.attach_current()
+    M.attach(util.current('buf'))
 end
 
 ---@private
@@ -109,6 +110,11 @@ function M.should_attach(buf)
         return false
     end
 
+    if not vim.api.nvim_buf_is_valid(buf) then
+        log.buf('info', 'attach', buf, 'skip', 'invalid')
+        return false
+    end
+
     local file_type, file_types = util.get('buf', buf, 'filetype'), state.file_types
     if not vim.tbl_contains(file_types, file_type) then
         local reason = string.format('%s /∈ %s', file_type, vim.inspect(file_types))

lua/render-markdown/state.lua

@@ -33,7 +33,7 @@ function M.setup(default_config, user_config)
     end
     -- Use lazy.nvim file type configuration if available and no user value is specified
     if user_config.file_types == nil then
-        local lazy_file_types = util.lazy_file_types('render-markdown.nvim')
+        local lazy_file_types = util.lazy('ft')
         if #lazy_file_types > 0 then
             config.file_types = lazy_file_types
         end