Merge pull request #3798 from jonozzz/fix-3751

Fix #3751

src/_pytest/main.py

@@ -505,8 +505,9 @@ def _collect(self, arg):
                             root = self._node_cache[pkginit]
                         else:
                             col = root._collectfile(pkginit)
-                            if col and isinstance(col, Package):
-                                root = col[0]
+                            if col:
+                                if isinstance(col[0], Package):
+                                    root = col[0]
                                 self._node_cache[root.fspath] = root
 
         # If it's a directory argument, recurse and look for any Subpackages.

testing/test_collection.py

@@ -638,16 +638,23 @@ def test_global_file(self, testdir, tmpdir):
             assert col.config is config
 
     def test_pkgfile(self, testdir):
+        """Verify nesting when a module is within a package.
+        The parent chain should match: Module<x.py> -> Package<subdir> -> Session.
+            Session's parent should always be None.
+        """
         tmpdir = testdir.tmpdir
         subdir = tmpdir.join("subdir")
         x = subdir.ensure("x.py")
         subdir.ensure("__init__.py")
         with subdir.as_cwd():
             config = testdir.parseconfigure(x)
         col = testdir.getnode(config, x)
-        assert isinstance(col, pytest.Module)
         assert col.name == "x.py"
-        assert col.parent.parent is None
+        assert isinstance(col, pytest.Module)
+        assert isinstance(col.parent, pytest.Package)
+        assert isinstance(col.parent.parent, pytest.Session)
+        # session is batman (has no parents)
+        assert col.parent.parent.parent is None
         for col in col.listchain():
             assert col.config is config