fix: pass opts.name to serpent to correct reference deserialize

Before, obj/func ref is sometimes deserialized as nil since:
1. serpent don't know who fn1 before the full table is returned since
   the serialized data is a compact version to ensure func/obj ref is
   consistant
2. lua table is random, so it's also possible to deserialize fn2
   correctly, but fn1=nil
```
return { fn1 = my_func, fn2 = fn1 }
```

Apply opts.name="_" for serpent, it would be like:
```
  local _ = { fn1 = my_func }
  _.fn2 = _.fn1
  return _
```

Author: phanen

lua/fzf-lua/libuv.lua

@@ -376,7 +376,7 @@ M.async_spawn = coroutinify(M.spawn)
 ---@param b64? boolean
 ---@return string, boolean -- boolean used for ./scripts/headless_fd.sh
 M.serialize = function(obj, b64)
-  local str = serpent.line(obj, { comment = false, sortkeys = false })
+  local str = serpent.line(obj, { name = "_", comment = false, sortkeys = false })
   str = b64 ~= false and base64.encode(str) or str
   return "return [==[" .. str .. "]==]", (b64 ~= false and true or false)
 end

lua/fzf-lua/previewer/builtin.lua

@@ -1565,13 +1565,12 @@ end
 
 ---@diagnostic disable-next-line: unused
 function Previewer.highlights:parse_entry(entry_str)
-  local serpent = require "fzf-lua.lib.serpent"
   local hl = entry_str:match("^[^%s]+")
   local hlgroup = hl
   local lines = {}
   repeat
     local hl_def = api.nvim_get_hl(0, { name = hl, link = true })
-    local block = utils.strsplit(serpent.block(hl_def, { comment = false, sortkeys = false }), "\n")
+    local block = utils.strsplit(vim.inspect(hl_def, { indent = (" "):rep(fn.shiftwidth()) }), "\n")
     block[1] = string.format("%s = %s", hl, block[1])
     vim.tbl_map(function(l) table.insert(lines, l) end, block)
     hl = hl_def.link

lua/fzf-lua/test/exec_lua.lua

@@ -197,7 +197,7 @@ M.serialize = function(...)
   for _, v in ipairs(args) do
     save_upvalues(v, args)
   end
-  return require("fzf-lua.lib.serpent").block(args, { comment = false, sortkeys = false })
+  return require("fzf-lua.lib.serpent").block(args, { name = "_", comment = false, sortkeys = false })
 end
 
 return M

tests/headless_spec.lua

@@ -38,10 +38,9 @@ local exec_term = function(c, cmd, args)
   cmd = cmd or {}
   args = args or {}
   args.term = true
-  local serpent = require "fzf-lua.lib.serpent"
-  cmd = serpent.block(cmd, { comment = false, sortkeys = false })
-  args = serpent.block(args, { comment = false, sortkeys = false })
-  local id = c.lua_get(string.format("vim.fn.jobstart(%s, %s)", cmd, args))
+  local id = c.lua(function()
+    return vim.fn.jobstart(cmd, args)
+  end)
   eq(tonumber(id) > 0, true)
   c.lua(string.format("vim.fn.jobwait({%s})", tostring(id)))
   c.wait_until(function()

tests/libuv_spec.lua

@@ -198,4 +198,16 @@ describe("Testing libuv module", function()
     vim.api.nvim_win_close(splitwin, true)
     FzfLua.utils.send_ctrl_c()
   end)
+
+  it("serialize/deserialize with shared function reference", function()
+    local func = function() return "test" end
+    local obj = { fn1 = func, fn2 = func }
+    local serialized = libuv.serialize(obj, false)
+    local deserialized = libuv.deserialize(serialized, false)
+    eq(type(deserialized.fn1), "function")
+    eq(type(deserialized.fn2), "function")
+    -- also verify both return the same value as original
+    eq(deserialized.fn1(), "test")
+    eq(deserialized.fn2(), "test")
+  end)
 end)