Create new dist option 'loadgroup'

src/xdist/scheduler/__init__.py

@@ -2,3 +2,4 @@ from xdist.scheduler.each import EachScheduling  # noqa
 from xdist.scheduler.load import LoadScheduling  # noqa
 from xdist.scheduler.loadfile import LoadFileScheduling  # noqa
 from xdist.scheduler.loadscope import LoadScopeScheduling  # noqa
+from xdist.scheduler.loadgroup import LoadGroupScheduling  # noqa

src/xdist/scheduler/loadgroup.py

@@ -0,0 +1,67 @@
+from .loadscope import LoadScopeScheduling
+from py.log import Producer
+
+
+class LoadGroupScheduling(LoadScopeScheduling):
+    """Implement load scheduling across nodes, but grouping test only has group mark.
+
+    This distributes the tests collected across all nodes so each test is run
+    just once.  All nodes collect and submit the list of tests and when all
+    collections are received it is verified they are identical collections.
+    Then the collection gets divided up in work units, grouped by group mark
+    (If there is no group mark, it is itself a group.), and those work units
+    et submitted to nodes. Whenever a node finishes an item, it calls
+    ``.mark_test_complete()`` which will trigger the scheduler to assign more
+    work units if the number of pending tests for the node falls below a low-watermark.
+
+    When created, ``numnodes`` defines how many nodes are expected to submit a
+    collection. This is used to know when all nodes have finished collection.
+
+    This class behaves very much like LoadScopeScheduling,
+    but with a itself or group(by marked) scope.
+    """
+
+    def __init__(self, config, log=None):
+        super().__init__(config, log)
+        if log is None:
+            self.log = Producer("loadgroupsched")
+        else:
+            self.log = log.loadgroupsched
+
+    def _split_scope(self, nodeid):
+        """Determine the scope (grouping) of a nodeid.
+
+        There are usually 3 cases for a nodeid::
+
+            example/loadsuite/test/test_beta.py::test_beta0
+            example/loadsuite/test/test_delta.py::Delta1::test_delta0
+            example/loadsuite/epsilon/__init__.py::epsilon.epsilon
+
+        #. Function in a test module.
+        #. Method of a class in a test module.
+        #. Doctest in a function in a package.
+
+        With loadgroup, two cases are added::
+
+            example/loadsuite/test/test_beta.py::test_beta0
+            example/loadsuite/test/test_delta.py::Delta1::test_delta0
+            example/loadsuite/epsilon/__init__.py::epsilon.epsilon
+            example/loadsuite/test/test_gamma.py::test_beta0@gname
+            example/loadsuite/test/test_delta.py::Gamma1::test_gamma0@gname
+
+        This function will group tests with the scope determined by splitting
+        the first ``@`` from the right. That is, test will be grouped in a
+        single work unit when they have same group name.
+         In the above example, scopes will be::
+
+            example/loadsuite/test/test_beta.py::test_beta0
+            example/loadsuite/test/test_delta.py::Delta1::test_delta0
+            example/loadsuite/epsilon/__init__.py::epsilon.epsilon
+            gname
+            gname
+        """
+        if nodeid.rfind("@") > nodeid.rfind("]"):
+            # check the index of ']' to avoid the case: parametrize mark value has '@'
+            return nodeid.split("@")[-1]
+        else:
+            return nodeid