From b82369a27533b04c2b9ce7e2e7d1821d5b278d8b Mon Sep 17 00:00:00 2001
From: Tom Minka <8955276+tminka@users.noreply.github.com>
Date: Mon, 4 Jan 2021 23:17:13 +0000
Subject: [PATCH] PyObject.AsManagedObject gives a better error message
 DelegateManager.TrueDispatch gives a better error message

---
 src/embed_tests/TestPyObject.cs | 10 +++++++++-
 src/runtime/delegatemanager.cs  | 24 +++++-------------------
 src/runtime/pyobject.cs         | 11 +++--------
 src/tests/test_delegate.py      | 21 ++++++++++++++++++++-
 4 files changed, 37 insertions(+), 29 deletions(-)

diff --git a/src/embed_tests/TestPyObject.cs b/src/embed_tests/TestPyObject.cs
index d4952d4a3..d0d8eab45 100644
--- a/src/embed_tests/TestPyObject.cs
+++ b/src/embed_tests/TestPyObject.cs
@@ -59,9 +59,17 @@ def add(self, x, y):
         }
 
         [Test]
-        public void InvokeNull() {
+        public void InvokeNull()
+        {
             var list = PythonEngine.Eval("list");
             Assert.Throws<ArgumentNullException>(() => list.Invoke(new PyObject[] {null}));
         }
+
+        [Test]
+        public void AsManagedObjectInvalidCast()
+        {
+            var list = PythonEngine.Eval("list");
+            Assert.Throws<InvalidCastException>(() => list.AsManagedObject(typeof(int)));
+        }
     }
 }
diff --git a/src/runtime/delegatemanager.cs b/src/runtime/delegatemanager.cs
index a8ab6d2b5..3e6541c44 100644
--- a/src/runtime/delegatemanager.cs
+++ b/src/runtime/delegatemanager.cs
@@ -221,19 +221,17 @@ public void Dispose()
         public object Dispatch(ArrayList args)
         {
             IntPtr gs = PythonEngine.AcquireLock();
-            object ob = null;
+            object ob;
 
             try
             {
                 ob = TrueDispatch(args);
             }
-            catch (Exception e)
+            finally
             {
                 PythonEngine.ReleaseLock(gs);
-                throw e;
             }
 
-            PythonEngine.ReleaseLock(gs);
             return ob;
         }
 
@@ -266,27 +264,15 @@ public object TrueDispatch(ArrayList args)
                 return null;
             }
 
-            object result = null;
-            if (!Converter.ToManaged(op, rtype, out result, false))
+            object result;
+            if (!Converter.ToManaged(op, rtype, out result, true))
             {
                 Runtime.XDecref(op);
-                throw new ConversionException($"could not convert Python result to {rtype}");
+                throw new PythonException();
             }
 
             Runtime.XDecref(op);
             return result;
         }
     }
-
-
-    public class ConversionException : Exception
-    {
-        public ConversionException()
-        {
-        }
-
-        public ConversionException(string msg) : base(msg)
-        {
-        }
-    }
 }
diff --git a/src/runtime/pyobject.cs b/src/runtime/pyobject.cs
index 524d6e4b6..d68a9905b 100644
--- a/src/runtime/pyobject.cs
+++ b/src/runtime/pyobject.cs
@@ -134,9 +134,9 @@ public static PyObject FromManagedObject(object ob)
         public object AsManagedObject(Type t)
         {
             object result;
-            if (!Converter.ToManaged(obj, t, out result, false))
+            if (!Converter.ToManaged(obj, t, out result, true))
             {
-                throw new InvalidCastException("cannot convert object to target type");
+                throw new InvalidCastException("cannot convert object to target type", new PythonException());
             }
             return result;
         }
@@ -154,12 +154,7 @@ public T As<T>()
             {
                 return (T)(this as object);
             }
-            object result;
-            if (!Converter.ToManaged(obj, typeof(T), out result, false))
-            {
-                throw new InvalidCastException("cannot convert object to target type");
-            }
-            return (T)result;
+            return (T)AsManagedObject(typeof(T));
         }
 
 
diff --git a/src/tests/test_delegate.py b/src/tests/test_delegate.py
index 1bfc4e903..909fd0f05 100644
--- a/src/tests/test_delegate.py
+++ b/src/tests/test_delegate.py
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-# TODO: Add test for ObjectDelegate
 
 """Test CLR delegate support."""
 
@@ -257,6 +256,26 @@ def always_so_negative():
     assert not d()
     assert not ob.CallBoolDelegate(d)
 
+def test_object_delegate():
+    """Test object delegate."""
+    from Python.Test import ObjectDelegate
+
+    def create_object():
+        return DelegateTest()
+
+    d = ObjectDelegate(create_object)
+    ob = DelegateTest()
+    ob.CallObjectDelegate(d)
+
+def test_invalid_object_delegate():
+    """Test invalid object delegate with mismatched return type."""
+    from Python.Test import ObjectDelegate
+
+    d = ObjectDelegate(hello_func)
+    ob = DelegateTest()
+    with pytest.raises(TypeError):
+        ob.CallObjectDelegate(d)
+
     # test async delegates
 
     # test multicast delegates

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