tags: auto-detect line numbers in tags file

lua/fzf-lua/make_entry.lua

@@ -323,11 +323,13 @@ M.tag = function(opts, x)
   if not file or not name or not text then return x end
   text = text:match('(.*);"') or text   -- remove ctag comments
   local line, tag = text:gsub("\\/", "/"):match("(%d-);?(/.*/)")
+  line = line and #line>0 and tonumber(line)
   return ("%s%s: %s %s"):format(
     M.file(opts, file),
-    (not line or #line==0) and "" or ":"..utils.ansi_codes.green(tostring(line)),
+    not line and "" or ":"..utils.ansi_codes.green(tostring(line)),
     utils.ansi_codes.magenta(name),
     utils.ansi_codes.green(tag))
+    , line
 end
 
 return M

lua/fzf-lua/providers/tags.lua

@@ -6,7 +6,7 @@ local make_entry = require "fzf-lua.make_entry"
 
 local M = {}
 
-local function get_tags_cmd(opts)
+local function get_tags_cmd(opts, flags)
   local query = nil
   local cmd = "grep"
   if vim.fn.executable("rg") == 1 then
@@ -20,7 +20,7 @@ local function get_tags_cmd(opts)
   else
     query = "-v '^!_TAG_'"
   end
-  return ("%s %s %s"):format(cmd, query,
+  return ("%s %s %s %s"):format(cmd, flags or '', query,
     vim.fn.shellescape(opts._ctags_file))
 end
 
@@ -40,6 +40,21 @@ local function tags(opts)
     return
   end
 
+  if opts.line_field_index == nil then
+    -- if caller did not specify the line field index
+    -- grep the first tag with '-m 1' and test for line presence
+    local cmd = get_tags_cmd({ _ctags_file = opts._ctags_file }, "-m 1")
+    local ok, lines, err = pcall(utils.io_systemlist, cmd)
+    if ok and err == 0 and lines and not vim.tbl_isempty(lines) then
+      local tag, line = make_entry.tag(opts, lines[1])
+      if tag and not line then
+        -- tags file does not contain lines
+        -- remove preview offset field index
+        opts.line_field_index = 0
+      end
+    end
+  end
+
   -- prevents 'file|git_icons=false' from overriding processing
   opts.requires_processing = true
   opts._fn_transform = make_entry.tag                            -- multiprocess=false