From e83a77591ebcd882e22ea15b49eab7c489ed3ee3 Mon Sep 17 00:00:00 2001
From: Victor Nova <lost@losttech.software>
Date: Wed, 28 Jul 2021 14:48:16 -0700
Subject: [PATCH] fixed custom decoders not working for DateTime and Decimal

---
 src/embed_tests/Codecs.cs | 44 +++++++++++++++++++++++++++++++++++++++
 src/runtime/converter.cs  | 24 ++++++++++++++-------
 2 files changed, 61 insertions(+), 7 deletions(-)

diff --git a/src/embed_tests/Codecs.cs b/src/embed_tests/Codecs.cs
index f0c00a6d8..e7303a8e4 100644
--- a/src/embed_tests/Codecs.cs
+++ b/src/embed_tests/Codecs.cs
@@ -355,6 +355,24 @@ public void ExceptionDecoded()
             Assert.AreEqual(TestExceptionMessage, error.Message);
         }
 
+        [Test]
+        public void DateTimeDecoded()
+        {
+            using var scope = Py.CreateScope();
+            scope.Exec(@"
+import clr
+from datetime import datetime
+
+
+from Python.EmbeddingTest import Codecs, DateTimeDecoder
+
+DateTimeDecoder.Setup()
+");
+            scope.Exec("Codecs.AcceptsDateTime(datetime(2021, 1, 22))");
+        }
+
+        public static void AcceptsDateTime(DateTime v) {}
+
         class ValueErrorWrapper : Exception
         {
             public ValueErrorWrapper(string message) : base(message) { }
@@ -419,4 +437,30 @@ public bool TryDecode<T>(PyObject pyObj, out T value)
             return true;
         }
     }
+
+    public class DateTimeDecoder : IPyObjectDecoder
+    {
+        public static void Setup()
+        {
+            PyObjectConversions.RegisterDecoder(new DateTimeDecoder());
+        }
+
+        public bool CanDecode(PyObject objectType, Type targetType)
+        {
+            return targetType == typeof(DateTime);
+        }
+
+        public bool TryDecode<T>(PyObject pyObj, out T value)
+        {
+            var dt = new DateTime(
+                pyObj.GetAttr("year").As<int>(),
+                pyObj.GetAttr("month").As<int>(),
+                pyObj.GetAttr("day").As<int>(),
+                pyObj.GetAttr("hour").As<int>(),
+                pyObj.GetAttr("minute").As<int>(),
+                pyObj.GetAttr("second").As<int>());
+            value = (T)(object)dt;
+            return true;
+        }
+    }
 }
diff --git a/src/runtime/converter.cs b/src/runtime/converter.cs
index 936f8b248..420fc9435 100644
--- a/src/runtime/converter.cs
+++ b/src/runtime/converter.cs
@@ -149,11 +149,8 @@ internal static IntPtr ToPython(object value, Type type)
                 return result;
             }
 
-            if (Type.GetTypeCode(type) == TypeCode.Object
-                && value.GetType() != typeof(object)
-                && value is not Type
-                || type.IsEnum
-            ) {
+            if (EncodableByUser(type, value))
+            {
                 var encoded = PyObjectConversions.TryEncode(value, type);
                 if (encoded != null) {
                     result = encoded.Handle;
@@ -301,6 +298,13 @@ internal static IntPtr ToPython(object value, Type type)
             }
         }
 
+        static bool EncodableByUser(Type type, object value)
+        {
+            TypeCode typeCode = Type.GetTypeCode(type);
+            return type.IsEnum
+                   || typeCode is TypeCode.DateTime or TypeCode.Decimal
+                   || typeCode == TypeCode.Object && value.GetType() != typeof(object) && value is not Type;
+        }
 
         /// <summary>
         /// In a few situations, we don't have any advisory type information
@@ -523,8 +527,7 @@ internal static bool ToManagedValue(IntPtr value, Type obType,
                 return false;
             }
 
-            TypeCode typeCode = Type.GetTypeCode(obType);
-            if (typeCode == TypeCode.Object || obType.IsEnum)
+            if (DecodableByUser(obType))
             {
                 IntPtr pyType = Runtime.PyObject_TYPE(value);
                 if (PyObjectConversions.TryDecode(value, pyType, obType, out result))
@@ -536,6 +539,13 @@ internal static bool ToManagedValue(IntPtr value, Type obType,
             return ToPrimitive(value, obType, out result, setError);
         }
 
+        static bool DecodableByUser(Type type)
+        {
+            TypeCode typeCode = Type.GetTypeCode(type);
+            return type.IsEnum
+                   || typeCode is TypeCode.Object or TypeCode.Decimal or TypeCode.DateTime;
+        }
+
         internal delegate bool TryConvertFromPythonDelegate(IntPtr pyObj, out object result);
 
         internal static int ToInt32(BorrowedReference value)