Use Config.invocation_params for consistent worker initialization

Decided to keep the old way still working for now.

Fix #6
Fix #445

changelog/448.feature.rst

@@ -0,0 +1,9 @@
+Initialization between workers and master nodes is now more consistent, which fixes a number of
+long-standing issues related to startup with the ``-c`` option.
+
+Issues:
+
+* `#6 <https://github.com/pytest-dev/pytest-xdist/issues/6>`__: Poor interaction between ``-n#`` and ``-c X.cfg``
+* `#445 <https://github.com/pytest-dev/pytest-xdist/issues/445>`__: pytest-xdist is not reporting the same nodeid as pytest does
+
+This however only works with **pytest 5.1 or later**, as it required changes in pytest itself.

src/xdist/remote.py

@@ -15,6 +15,8 @@ import _pytest.hookspec
 import pytest
 from execnet.gateway_base import dumps, DumpError
 
+from _pytest.config import _prepareconfig, Config
+
 
 class WorkerInteractor(object):
     def __init__(self, config, channel):
@@ -211,18 +213,18 @@ def getinfodict():
 
 
 def remote_initconfig(option_dict, args):
-    from _pytest.config import Config
-
     option_dict["plugins"].append("no:terminal")
-    config = Config.fromdictargs(option_dict, args)
+    return Config.fromdictargs(option_dict, args)
+
+
+def setup_config(config, basetemp):
     config.option.looponfail = False
     config.option.usepdb = False
     config.option.dist = "no"
     config.option.distload = False
     config.option.numprocesses = None
     config.option.maxprocesses = None
-    config.args = args
-    return config
+    config.option.basetemp = basetemp
 
 
 if __name__ == "__channelexec__":
@@ -239,7 +241,13 @@ if __name__ == "__channelexec__":
     os.environ["PYTEST_XDIST_WORKER"] = workerinput["workerid"]
     os.environ["PYTEST_XDIST_WORKER_COUNT"] = str(workerinput["workercount"])
 
-    config = remote_initconfig(option_dict, args)
+    if hasattr(Config, "InvocationParams"):
+        config = _prepareconfig(args, None)
+    else:
+        config = remote_initconfig(option_dict, args)
+        config.args = args
+
+    setup_config(config, option_dict.get("basetemp"))
     config._parser.prog = os.path.basename(workerinput["mainargv"][0])
     config.workerinput = workerinput
     config.workeroutput = {}

src/xdist/workermanage.py

@@ -186,6 +186,8 @@ def make_reltoroot(roots, args):
     for arg in args:
         parts = arg.split(splitcode)
         fspath = py.path.local(parts[0])
+        if not fspath.exists():
+            continue
         for root in roots:
             x = fspath.relto(root)
             if x or fspath == root:
@@ -236,10 +238,14 @@ class WorkerController(object):
     def setup(self):
         self.log("setting up worker session")
         spec = self.gateway.spec
-        args = self.config.args
+        if hasattr(self.config, "invocation_params"):
+            args = [str(x) for x in self.config.invocation_params.args or ()]
+            option_dict = {}
+        else:
+            args = self.config.args
+            option_dict = vars(self.config.option)
         if not spec.popen or spec.chdir:
             args = make_reltoroot(self.nodemanager.roots, args)
-        option_dict = vars(self.config.option)
         if spec.popen:
             name = "popen-%s" % self.gateway.id
             if hasattr(self.config, "_tmpdirhandler"):

testing/acceptance_test.py

@@ -559,6 +559,30 @@ def test_fixture_teardown_failure(testdir):
     assert result.ret
 
 
+def test_config_initialization(testdir, pytestconfig):
+    """Ensure workers and master are initialized consistently. Integration test for #445"""
+    if not hasattr(pytestconfig, "invocation_params"):
+        pytest.skip(
+            "requires pytest >=5.1 (config has no attribute 'invocation_params')"
+        )
+    testdir.makepyfile(
+        **{
+            "dir_a/test_foo.py": """
+                def test_1(): pass
+        """
+        }
+    )
+    testdir.makefile(
+        ".ini",
+        myconfig="""
+        [pytest]
+        testpaths=dir_a
+    """,
+    )
+    result = testdir.runpytest("-n2", "-c", "myconfig.ini", "-v")
+    result.stdout.fnmatch_lines(["dir_a/test_foo.py::test_1*"])
+
+
 @pytest.mark.parametrize("when", ["setup", "call", "teardown"])
 def test_crashing_item(testdir, when):
     """Ensure crashing item is correctly reported during all testing stages"""