Fix warnings transfer between workers and master node with pytest >= 3.8

Fix #341

xdist/dsession.py

@@ -270,6 +270,11 @@ class DSession(object):
         kwargs = dict(message=message, code=code, nodeid=nodeid, fslocation=fslocation)
         self.config.hook.pytest_logwarning.call_historic(kwargs=kwargs)
 
+    def worker_warning_captured(self, warning_message, when, item):
+        """Emitted when a node calls the pytest_logwarning hook."""
+        kwargs = dict(warning_message=warning_message, when=when, item=item)
+        self.config.hook.pytest_warning_captured.call_historic(kwargs=kwargs)
+
     def _clone_node(self, node):
         """Return new node based on an existing one.
 

xdist/remote.py

@@ -123,6 +123,18 @@ class WorkerInteractor(object):
             fslocation=str(fslocation),
         )
 
+    # the pytest_warning_captured hook was introduced in pytest 3.8
+    if hasattr(_pytest.hookspec, "pytest_warning_captured"):
+
+        def pytest_warning_captured(self, warning_message, when, item):
+            self.sendevent(
+                "warning_captured",
+                warning_message_data=serialize_warning_message(warning_message),
+                when=when,
+                # item cannot be serialized and will always be None when used with xdist
+                item=None,
+            )
+
 
 def serialize_report(rep):
     def disassembled_report(rep):
@@ -165,6 +177,40 @@ def serialize_report(rep):
     return d
 
 
+def serialize_warning_message(warning_message):
+    if isinstance(warning_message.message, Warning):
+        message_module = type(warning_message.message).__module__
+        message_class_name = type(warning_message.message).__name__
+        message_args = warning_message.message.args
+        message_str = None
+    else:
+        message_str = warning_message.message
+        message_module = None
+        message_class_name = None
+        message_args = None
+    if warning_message.category:
+        category_module = warning_message.category.__module__
+        category_class_name = warning_message.category.__name__
+    else:
+        category_module = None
+        category_class_name = None
+
+    result = {
+        "message_str": message_str,
+        "message_module": message_module,
+        "message_class_name": message_class_name,
+        "message_args": message_args,
+        "category_module": category_module,
+        "category_class_name": category_class_name,
+    }
+    # access private _WARNING_DETAILS because the attributes vary between Python versions
+    for attr_name in warning_message._WARNING_DETAILS:
+        if attr_name in ("message", "category"):
+            continue
+        result[attr_name] = getattr(warning_message, attr_name)
+    return result
+
+
 def getinfodict():
     import platform
 

xdist/workermanage.py

@@ -327,6 +327,16 @@ class WorkerController(object):
                     nodeid=kwargs["nodeid"],
                     fslocation=kwargs["nodeid"],
                 )
+            elif eventname == "warning_captured":
+                warning_message = unserialize_warning_message(
+                    kwargs["warning_message_data"]
+                )
+                self.notify_inproc(
+                    eventname,
+                    warning_message=warning_message,
+                    when=kwargs["when"],
+                    item=kwargs["item"],
+                )
             else:
                 raise ValueError("unknown event: %s" % (eventname,))
         except KeyboardInterrupt:
@@ -409,6 +419,33 @@ def unserialize_report(name, reportdict):
         return runner.CollectReport(**assembled_report(reportdict))
 
 
+def unserialize_warning_message(data):
+    import warnings
+    import importlib
+
+    if data["message_module"]:
+        mod = importlib.import_module(data["message_module"])
+        cls = getattr(mod, data["message_class_name"])
+        message = cls(*data["message_args"])
+    else:
+        message = data["message_str"]
+
+    if data["category_module"]:
+        mod = importlib.import_module(data["category_module"])
+        category = getattr(mod, data["category_class_name"])
+    else:
+        category = None
+
+    kwargs = {"message": message, "category": category}
+    # access private _WARNING_DETAILS because the attributes vary between Python versions
+    for attr_name in warnings.WarningMessage._WARNING_DETAILS:
+        if attr_name in ("message", "category"):
+            continue
+        kwargs[attr_name] = data[attr_name]
+
+    return warnings.WarningMessage(**kwargs)
+
+
 def report_unserialization_failure(type_name, report_name, reportdict):
     from pprint import pprint