fix(multithreading): support new lane:join() API

Author: Aire-One

src/luacheck/multithreading.lua

@@ -1,3 +1,7 @@
+-- luacheck: push compat
+local unpack = table.unpack or unpack
+-- luacheck: pop
+
 local utils = require "luacheck.utils"
 
 local multithreading = {}
@@ -12,6 +16,8 @@ if not lanes_ok then
    return multithreading
 end
 
+local lanes_major = tonumber(lanes.ABOUT.version:match("^(%d+)"))
+
 local cpu_number_detection_commands = {}
 
 if utils.is_windows then
@@ -90,7 +96,18 @@ function multithreading.pmap(func, array, jobs)
    local results = {}
 
    for _, worker in ipairs(workers) do
-      local _, ok, worker_results = assert(worker:join())
+      local join_results = {worker:join()}
+
+      -- Manage both new and old lane:join() API formats.
+      -- See https://github.com/LuaLanes/lanes/commit/bfdc7a92c4e3e99522abb6d90ef2cbb021f36fc8
+      local ok, worker_results, _
+      if  lanes_major >= 4 then
+         -- New API: {true, _, ok, worker_results}
+         _, _, ok, worker_results = unpack(join_results)
+      else
+         -- Old API: {true, ok, worker_results}
+         _, ok, worker_results = unpack(join_results)
+      end
 
       if ok then
          utils.update(results, worker_results)