Use pytest_xdist_make_scheduler hook to set up scheduller instance

xdist/dsession.py

@@ -485,17 +485,6 @@ class DSession:
             self.trdist = TerminalDistReporter(config)
             config.pluginmanager.register(self.trdist, "terminaldistreporter")
 
-        self.sched = None
-        dist = self.config.getvalue("dist")
-        if dist == "load":
-            self.ScheduleCls = LoadScheduling
-        elif dist == "each":
-            self.ScheduleCls = EachScheduling
-        else:
-            mod_name, cls_name = dist.rsplit('.', 1)
-            mod = __import__(mod_name)
-            self.ScheduleCls = getattr(mod, cls_name)
-
     @property
     def session_finished(self):
         """Return True if the distributed session has finished
@@ -532,11 +521,22 @@ class DSession:
         # prohibit collection of test items in master process
         return True
 
+    @pytest.hookimpl(trylast=True)
+    def pytest_xdist_make_scheduler(self, numnodes, log, config):
+        dist = config.getvalue("dist")
+        if dist == "load":
+            return LoadScheduling(numnodes, log=log, config=config)
+        elif dist == "each":
+            return EachScheduling(numnodes, log=log, config=config)
+
     def pytest_runtestloop(self):
         numnodes = len(self.nodemanager.specs)
+        self.sched = self.config.hook.pytest_xdist_make_scheduler(numnodes=numnodes,
+                                                                  log=self.log,
+                                                                  config=self.config)
+        assert self.sched is not None
+
         self.shouldstop = False
-        self.sched = self.ScheduleCls(numnodes, log=self.log,
-                                      config=self.config)
         while not self.session_finished:
             self.loop_once()
             if self.shouldstop:

xdist/newhooks.py

@@ -11,6 +11,7 @@ must be taken in plugins in case ``xdist`` is not installed. Please see:
 
     http://pytest.org/latest/writing_plugins.html#optionally-using-hooks-from-3rd-party-plugins
 """
+import pytest
 
 
 def pytest_xdist_setupnodes(config, specs):
@@ -44,3 +45,9 @@ def pytest_testnodedown(node, error):
 def pytest_xdist_node_collection_finished(node, ids):
     """called by the master node when a node finishes collecting.
     """
+
+
+@pytest.hookspec(firstresult=True)
+def pytest_xdist_make_scheduler(numnodes, log, config):
+    """Return a node scheduler implementation, or None.
+    """

xdist/plugin.py

@@ -37,8 +37,6 @@ def pytest_addoption(parser):
               "each: send each test to each available environment.\n\n"
               "load: send each test to available environment.\n\n"
               "(default) no: run tests inprocess, don't distribute."))
-    group._addoption('--dc', dest='distcustom',
-                     help="Custom scheduler implementation")
     group._addoption(
         '--tx', dest="tx", action="append", default=[],
         metavar="xspec",
@@ -101,8 +99,6 @@ def pytest_cmdline_main(config):
         config.option.tx = ['popen'] * config.option.numprocesses
     if config.option.distload:
         config.option.dist = "load"
-    if config.option.distcustom:
-        config.option.dist = config.option.distcustom
     val = config.getvalue
     if not val("collectonly"):
         usepdb = config.getoption('usepdb')  # a core option

xdist/remote.py

@@ -131,7 +131,6 @@ def remote_initconfig(option_dict, args):
     config.option.usepdb = False
     config.option.dist = "no"
     config.option.distload = False
-    config.option.distcustom = None
     config.option.numprocesses = None
     config.args = args
     return config