Fix passing --basetemp to subprocesses with pytest 5.4

Fixes pytest-dev#510.
Ref: pytest-dev/pytest#6767

Also uses `--basetemp` with `-p no:tmpdir` as a good side effect
(ref: pytest-dev#22).

changelog/510.bugfix.rst

@@ -0,0 +1 @@
+Fix passing `--basetemp` to subprocesses with pytest 5.4.

src/xdist/workermanage.py

@@ -1,12 +1,14 @@
 from __future__ import print_function
+
 import fnmatch
 import os
 import re
 import sys
 
+import execnet
 import py
 import pytest
-import execnet
+from _pytest.tmpdir import TempPathFactory
 
 import xdist.remote
 
@@ -252,9 +254,9 @@ def setup(self):
             args = make_reltoroot(self.nodemanager.roots, args)
         if spec.popen:
             name = "popen-%s" % self.gateway.id
-            if hasattr(self.config, "_tmpdirhandler"):
-                basetemp = self.config._tmpdirhandler.getbasetemp()
-                option_dict["basetemp"] = str(basetemp.join(name))
+            basetemp = TempPathFactory.from_config(self.config).getbasetemp()
+            option_dict["basetemp"] = str(basetemp.joinpath(name))
+
         self.config.hook.pytest_configure_node(node=self)
 
         remote_module = self.config.hook.pytest_xdist_getremotemodule()

testing/acceptance_test.py

@@ -766,9 +766,11 @@ def test_tmpdir_disabled(testdir):
     """
     p1 = testdir.makepyfile(
         """
-        def test_ok():
-            pass
-    """
+        def test_ok(request):
+            assert request.config.option.basetemp == {!r}
+    """.format(
+            str(testdir.tmpdir.dirpath() / "basetemp" / "popen-gw0")
+        )
     )
     result = testdir.runpytest(p1, "-n1", "-p", "no:tmpdir")
     assert result.ret == 0