[PyROOT] Take ownership of objects returned by TDirectoryFile.Get that are not owned by the directory

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_tdirectoryfile.py

@@ -69,7 +69,12 @@ def _TDirectoryFile_Get(self, namecycle):
     if key:
         class_name = key.GetClassName()
         address = self.GetObjectChecked(namecycle, class_name)
-        return ROOT._cppyy.bind_object(address, class_name)
+        obj = ROOT._cppyy.bind_object(address, class_name)
+        # Objects that are not registered in the directory (e.g. TGraph or
+        # non-TObjects like ROOT::RNTuple) are owned by the caller
+        if address and not (isinstance(obj, ROOT.TObject) and self.GetList().FindObject(obj)):
+            ROOT.SetOwnership(obj, True)
+        return obj
     # no key? for better or worse, call normal Get()
     return self._Get(namecycle)
 

bindings/pyroot/pythonizations/test/tdirectory_tfile.py

@@ -210,6 +210,53 @@ def test_keys_title(self):
         finput.Close()
 
 
+class TFileGetOwnership(unittest.TestCase):
+    """
+    Test that the objects returned by Get are owned by Python unless they are
+    owned by the directory (#16178)
+    """
+
+    filename = "tfilegetownership.root"
+
+    @classmethod
+    def setUpClass(cls):
+        with TFile(cls.filename, "recreate") as f:
+            ROOT.TH1F("h", "h", 10, 0, 1).Write()
+            ROOT.TTree("t", "t").Write()
+            f.mkdir("dir")
+            ROOT.TGraph(10).Write("g")
+            ROOT.TObjString("s").Write("s")
+            f.WriteObject(ROOT.std.vector["double"](10), "v")
+
+    @classmethod
+    def tearDownClass(cls):
+        os.remove(cls.filename)
+
+    def test_owned_by_directory(self):
+        with TFile(self.filename) as f:
+            for name in ["h", "t", "dir"]:
+                obj = f.Get(name)
+                # Whether these objects are registered in the directory may
+                # depend on ROOT::Experimental::ObjectAutoRegistrationEnabled()
+                # in the future, so check the ownership against the actual
+                # registration
+                registered = bool(f.GetList().FindObject(name))
+                self.assertEqual(obj.__python_owns__, not registered, msg=name)
+                # The object is still alive
+                self.assertEqual(f.Get(name).GetName(), name)
+
+    def test_owned_by_python(self):
+        with TFile(self.filename) as f:
+            objs = {name: f.Get(name) for name in ["g", "s", "v"]}
+            for name, obj in objs.items():
+                self.assertTrue(obj.__python_owns__, msg=name)
+                self.assertFalse(f.GetList().FindObject(name), msg=name)
+        # The objects are still usable after the file is closed
+        self.assertEqual(objs["g"].GetN(), 10)
+        self.assertEqual(objs["s"].GetString(), "s")
+        self.assertEqual(objs["v"].size(), 10)
+
+
 class TFileConstructor(unittest.TestCase):
     """
     Test for the TFile constructor