feat(pack): hint in confirmation buffer that plugin is not active

Problem: After `vim.pack.update()` it is not clear if plugin is active
  or not. This can be useful to detect cases when plugin was removed
  from 'init.lua' but there was no `vim.pack.del()`.

Solution: Add ` (not active)` suffix with distinctive highlighting to
  header of plugins that are not active.
  It will also be shown in in-process LSP document symbols to have quick
  reference about which plugins are not active.

runtime/ftplugin/nvim-pack.lua

@@ -25,8 +25,10 @@ for i, l in ipairs(lines) do
     cur_header_hl_group = header_hl_groups[cur_group]
     hi_range(i, 0, l:len(), cur_header_hl_group)
   elseif l:find('^## (.+)$') ~= nil then
-    -- Header 2
+    -- Header 2 with possibly "(not active)" suffix
     hi_range(i, 0, l:len(), cur_header_hl_group)
+    local col = l:match('() %(not active%)$') or l:len()
+    hi_range(i, col, l:len(), 'DiagnosticError', priority + 1)
   elseif cur_info ~= nil then
     -- Plugin info
     local end_col = l:match('(). +%b()$') or l:len()

runtime/lua/vim/pack.lua

@@ -990,11 +990,12 @@ end
 --- @param p vim.pack.Plug
 --- @return string
 local function compute_feedback_lines_single(p)
+  local active_suffix = active_plugins[p.path] ~= nil and '' or ' (not active)'
   if p.info.err ~= '' then
-    return ('## %s\n\n %s'):format(p.spec.name, p.info.err:gsub('\n', '\n  '))
+    return ('## %s%s\n\n %s'):format(p.spec.name, active_suffix, p.info.err:gsub('\n', '\n  '))
   end
 
-  local parts = { '## ' .. p.spec.name .. '\n' }
+  local parts = { ('## %s%s\n'):format(p.spec.name, active_suffix) }
   local version_suffix = p.info.version_str == '' and '' or (' (%s)'):format(p.info.version_str)
 
   if p.info.sha_head == p.info.sha_target then
@@ -1127,7 +1128,7 @@ local function get_update_map(bufnr)
   for _, l in ipairs(lines) do
     local name = l:match('^## (.+)$')
     if name and is_in_update then
-      res[name] = true
+      res[name:gsub(' %(not active%)$', '')] = true
     end
 
     local group = l:match('^# (%S+)')

runtime/lua/vim/pack/_lsp.lua

@@ -59,7 +59,7 @@ local get_plug_data_at_lnum = function(bufnr, lnum)
   if not (from <= lnum and lnum <= to) then
     return {}
   end
-  return { group = group, name = name, from = from, to = to }
+  return { group = group, name = name:gsub(' %(not active%)$', ''), from = from, to = to }
 end
 
 --- @alias vim.pack.lsp.Position { line: integer, character: integer }

test/functional/plugin/pack_spec.lua

@@ -1622,6 +1622,29 @@ describe('vim.pack', function()
         ref_fetch_lock.rev = git_get_hash('main', 'fetch')
         eq(ref_fetch_lock, get_lock_tbl().plugins.fetch)
       end)
+
+      it('hints about not active plugins', function()
+        exec_lua(function()
+          vim.pack.update()
+        end)
+
+        for _, l in ipairs(api.nvim_buf_get_lines(0, 0, -1, false)) do
+          if l:match('^## ') then
+            matches(' %(not active%)$', l)
+          end
+        end
+
+        -- Should also hint in `textDocument/documentSymbol` of in-process LSP,
+        -- yet still work for navigation
+        exec_lua('vim.lsp.buf.document_symbol()')
+        local loclist = fn.getloclist(0)
+        matches(' %(not active%)$', loclist[2].text)
+        matches(' %(not active%)$', loclist[4].text)
+        matches(' %(not active%)$', loclist[5].text)
+
+        n.exec('llast')
+        eq(21, api.nvim_win_get_cursor(0)[1])
+      end)
     end)
 
     it('works with not active plugins', function()