clear weak reference list when an extension type is destroyed

lostmsu · lostmsu · commit 7fa3e8e3b5de · 2022-04-09T13:48:17.000-07:00
According to official documentation for defining extension types, if they are to support weak references, they must clear weak reference list associated with the instance in tp_clear. Extension types were missed in pythonnet#1758 ( 50da522 )
diff --git a/src/embed_tests/ExtensionTypes.cs b/src/embed_tests/ExtensionTypes.cs
@@ -0,0 +1,32 @@
+using System;
+
+using NUnit.Framework;
+
+using Python.Runtime;
+
+namespace Python.EmbeddingTest;
+
+public class ExtensionTypes
+{
+    [OneTimeSetUp]
+    public void SetUp()
+    {
+        PythonEngine.Initialize();
+    }
+
+    [OneTimeTearDown]
+    public void Dispose()
+    {
+        PythonEngine.Shutdown();
+    }
+
+    [Test]
+    public void WeakrefIsNone_AfterBoundMethodIsGone()
+    {
+        using var makeref = Py.Import("weakref").GetAttr("ref");
+        var boundMethod = new UriBuilder().ToPython().GetAttr(nameof(UriBuilder.GetHashCode));
+        var weakref = makeref.Invoke(boundMethod);
+        boundMethod.Dispose();
+        Assert.IsTrue(weakref.Invoke().IsNone());
+    }
+}
diff --git a/src/runtime/Types/ExtensionType.cs b/src/runtime/Types/ExtensionType.cs
@@ -86,6 +86,12 @@ public unsafe static void tp_dealloc(NewReference lastRef)
 
         public static int tp_clear(BorrowedReference ob)
         {
+            var weakrefs = Runtime.PyObject_GetWeakRefList(ob);
+            if (weakrefs != null)
+            {
+                Runtime.PyObject_ClearWeakRefs(ob);
+            }
+
             if (TryFreeGCHandle(ob))
             {
                 bool deleted = loadedExtensions.Remove(ob.DangerousGetAddress());
diff --git a/src/runtime/Types/MetaType.cs b/src/runtime/Types/MetaType.cs
@@ -273,6 +273,12 @@ public static NewReference mp_subscript(BorrowedReference tp, BorrowedReference
         /// </summary>
         public static void tp_dealloc(NewReference lastRef)
         {
+            var weakrefs = Runtime.PyObject_GetWeakRefList(lastRef.Borrow());
+            if (weakrefs != null)
+            {
+                Runtime.PyObject_ClearWeakRefs(lastRef.Borrow());
+            }
+
             // Fix this when we dont cheat on the handle for subclasses!
 
             var flags = PyType.GetFlags(lastRef.Borrow());

Original file line number	Diff line number	Diff line change
`@@ -86,6 +86,12 @@ public unsafe static void tp_dealloc(NewReference lastRef)`
`86`	`86`
`87`	`87`	`public static int tp_clear(BorrowedReference ob)`
`88`	`88`	`{`
	`89`	`+ var weakrefs = Runtime.PyObject_GetWeakRefList(ob);`
	`90`	`+ if (weakrefs != null)`
	`91`	`+ {`
	`92`	`+ Runtime.PyObject_ClearWeakRefs(ob);`
	`93`	`+ }`
	`94`	`+`
`89`	`95`	`if (TryFreeGCHandle(ob))`
`90`	`96`	`{`
`91`	`97`	`bool deleted = loadedExtensions.Remove(ob.DangerousGetAddress());`