New methods is_xdist_worker, is_xdist_master, get_xdist_worker_id. Fixes pytest-dev#504

Author: Sylvain MARIE

src/xdist/__init__.py

@@ -1,3 +1,5 @@
+from xdist.plugin import is_xdist_worker, is_xdist_master, get_xdist_worker_id
 from xdist._version import version as __version__
 
-__all__ = ["__version__"]
+__all__ = ['__version__',
+           'is_xdist_worker', 'is_xdist_master', 'get_xdist_worker_id']

src/xdist/plugin.py

@@ -201,16 +201,49 @@ def pytest_cmdline_main(config):
 
 
 # -------------------------------------------------------------------------
-# fixtures
+# fixtures and API to easily know the role of current node
 # -------------------------------------------------------------------------
 
+def is_xdist_worker(request_or_session):
+    """Return `True` if this is an xdist worker, `False` otherwise
 
-@pytest.fixture(scope="session")
-def worker_id(request):
+    :param request_or_session: the `pytest` `request` or `session` object
+    :return:
+    """
+    return hasattr(request_or_session.config, "workerinput")
+
+
+def is_xdist_master(request_or_session):
+    """Return `True` if this is the xdist master, `False` otherwise
+
+    Note: this method also returns `False` when distribution has not been
+    activated at all.
+
+    :param request_or_session: the `pytest` `request` or `session` object
+    :return:
+    """
+    return (not is_xdist_worker(request_or_session)
+            and request_or_session.config.option.dist != "no")
+
+
+def get_xdist_worker_id(request_or_session):
     """Return the id of the current worker ('gw0', 'gw1', etc) or 'master'
     if running on the master node.
+
+    :param request_or_session: the `pytest` `request` or `session` object
+    :return:
     """
-    if hasattr(request.config, "workerinput"):
-        return request.config.workerinput["workerid"]
+    if hasattr(request_or_session.config, "workerinput"):
+        return request_or_session.config.workerinput["workerid"]
     else:
+        # TODO shall we raise an exception if dist is not enabled ?
+        #  i.e. `not is_xdist_master(request_or_session)` ?
         return "master"
+
+
+@pytest.fixture(scope="session")
+def worker_id(request):
+    """Return the id of the current worker ('gw0', 'gw1', etc) or 'master'
+    if running on the master node.
+    """
+    return get_xdist_worker_id(request)