Avoid crash for sybil doctests

src/pytest_run_parallel/plugin.py

@@ -254,7 +254,13 @@ def pytest_collection_finish(self, session):
             self._handle_collected_item(item)
 
     def _handle_collected_item(self, item):
-        if not hasattr(item, "obj"):
+        if isinstance(item, _pytest.doctest.DoctestItem):
+            self._mark_test_thread_unsafe(
+                item, "is a doctest (pytest-run-parallel does not support doctests)"
+            )
+            return
+
+        if getattr(item, "obj", None) is None:
             if not hasattr(item, "_parallel_custom_item"):
                 warnings.warn(
                     f"Encountered pytest item with type {type(item)} with no 'obj' "
@@ -273,12 +279,6 @@ def _handle_collected_item(self, item):
             )
             return
 
-        if isinstance(item, _pytest.doctest.DoctestItem):
-            self._mark_test_thread_unsafe(
-                item, "is a doctest (pytest-run-parallel does not support doctests)"
-            )
-            return
-
         n_workers, parallel_threads_marker_used = get_num_workers(item)
         if n_workers < 0:
             raise ValueError("parallel-threads cannot be negative")

tests/test_run_parallel.py

@@ -579,7 +579,10 @@ def test_should_skip():
     )
 
 
-def test_incompatible_test_item(pytester):
+def test_incompatible_test_item_no_obj_item(pytester):
+    """Doctests and other doctest-like custom pytest.Item subclasses are incompatible
+    without an obj attribute on the Item. This shouldn't crash pytest-run-parallel
+    and the test should only run on one thread"""
     pytester.makeconftest("""
     import inspect
     import pytest
@@ -615,7 +618,50 @@ def test_incompatible_item():
     assert result.parseoutcomes()["warnings"] == 1
 
 
+def test_incompatible_test_item_obj_is_none(pytester):
+    """Doctests and other doctest-like custom pytest.Item subclasses are incompatible
+    if the obj attribute is None. This shouldn't crash pytest-run-parallel
+    and the test should only run on one thread"""
+    pytester.makeconftest("""
+    import inspect
+    import pytest
+
+    class CustomItem(pytest.Item):
+        def __init__(self, name, parent=None, config=None, session=None, nodeid=None, function=None, **kwargs):
+            super().__init__(name, parent, config, session, nodeid, **kwargs)
+            self.function = function
+            self.obj = None
+
+        def runtest(self):
+            self.function()
+
+    @pytest.hookimpl(wrapper=True, trylast=True)
+    def pytest_pycollect_makeitem(collector, name: str, obj: object):
+        result = yield
+        if not inspect.isfunction(obj):
+            return result
+        return CustomItem.from_parent(name=name, parent=collector, function=obj)
+    """)
+
+    pytester.makepyfile("""
+    import pytest
+
+    def test_incompatible_item():
+        assert True
+    """)
+    result = pytester.runpytest("--parallel-threads=10", "-v", "-W", "default")
+    result.stdout.fnmatch_lines(
+        [
+            "*::test_incompatible_item PASSED*",
+        ]
+    )
+    assert result.parseoutcomes()["warnings"] == 1
+    result.stdout.fnmatch_lines(["*Encountered pytest item * with no 'obj' attribute*"])
+
+
 def test_known_incompatible_test_item_doesnt_warn(pytester):
+    """If the Item has a _parallel_custom_item attribute, pytest-run-parallel
+    shouldn't warn about the incompatibility"""
     pytester.makeconftest("""
     import inspect
     import pytest