provide `__int__` instance method on .NET enum types to support int(Enum.Member) (#1661)

implements https://github.com/pythonnet/pythonnet/issues/1585

src/runtime/classmanager.cs

@@ -346,8 +346,7 @@ namespace Python.Runtime
                 }
             }
 
-            // only [Flags] enums support bitwise operations
-            if (type.IsEnum && type.IsFlagsEnum())
+            if (type.IsEnum)
             {
                 var opsImpl = typeof(EnumOps<>).MakeGenericType(type);
                 foreach (var op in opsImpl.GetMethods(OpsHelper.BindingFlags))
@@ -355,6 +354,17 @@ namespace Python.Runtime
                     local.Add(op.Name);
                 }
                 info = info.Concat(opsImpl.GetMethods(OpsHelper.BindingFlags)).ToArray();
+
+                // only [Flags] enums support bitwise operations
+                if (type.IsFlagsEnum())
+                {
+                    opsImpl = typeof(FlagEnumOps<>).MakeGenericType(type);
+                    foreach (var op in opsImpl.GetMethods(OpsHelper.BindingFlags))
+                    {
+                        local.Add(op.Name);
+                    }
+                    info = info.Concat(opsImpl.GetMethods(OpsHelper.BindingFlags)).ToArray();
+                }
             }
 
             // Now again to filter w/o losing overloaded member info

src/runtime/native/ITypeOffsets.cs

@@ -21,6 +21,7 @@ namespace Python.Runtime.Native
         int nb_multiply { get; }
         int nb_true_divide { get; }
         int nb_and { get; }
+        int nb_int { get; }
         int nb_or { get; }
         int nb_xor { get; }
         int nb_lshift { get; }

src/runtime/native/TypeOffset.cs

@@ -30,6 +30,7 @@ namespace Python.Runtime
         internal static int nb_and { get; private set; }
         internal static int nb_or { get; private set; }
         internal static int nb_xor { get; private set; }
+        internal static int nb_int { get; private set; }
         internal static int nb_lshift { get; private set; }
         internal static int nb_rshift { get; private set; }
         internal static int nb_remainder { get; private set; }

src/runtime/operatormethod.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using System.Reflection;
-using System.Runtime.InteropServices;
 using System.Text;
 
 namespace Python.Runtime
@@ -51,6 +51,8 @@ namespace Python.Runtime
                 ["op_OnesComplement"] = new SlotDefinition("__invert__", TypeOffset.nb_invert),
                 ["op_UnaryNegation"] = new SlotDefinition("__neg__", TypeOffset.nb_negative),
                 ["op_UnaryPlus"] = new SlotDefinition("__pos__", TypeOffset.nb_positive),
+
+                ["__int__"] = new SlotDefinition("__int__", TypeOffset.nb_int),
             };
             ComparisonOpMap = new Dictionary<string, string>
             {
@@ -97,14 +99,11 @@ namespace Python.Runtime
         /// </summary>
         public static void FixupSlots(BorrowedReference pyType, Type clrType)
         {
-            const BindingFlags flags = BindingFlags.Public | BindingFlags.Static;
             Debug.Assert(_opType != null);
 
-            var staticMethods =
-                clrType.IsEnum ? typeof(EnumOps<>).MakeGenericType(clrType).GetMethods(flags)
-                : clrType.GetMethods(flags);
+            var operatorCandidates = GetOperatorCandidates(clrType);
 
-            foreach (var method in staticMethods)
+            foreach (var method in operatorCandidates)
             {
                 // We only want to override slots for operators excluding
                 // comparison operators, which are handled by ClassBase.tp_richcompare.
@@ -124,6 +123,18 @@ namespace Python.Runtime
             }
         }
 
+        static IEnumerable<MethodInfo> GetOperatorCandidates(Type clrType)
+        {
+            const BindingFlags flags = BindingFlags.Public | BindingFlags.Static;
+            if (clrType.IsEnum)
+            {
+                return typeof(EnumOps<>).MakeGenericType(clrType).GetMethods(flags)
+                    .Concat(typeof(FlagEnumOps<>).MakeGenericType(clrType).GetMethods(flags));
+            }
+
+            return clrType.GetMethods(flags);
+        }
+
         public static string GetPyMethodName(string clrName)
         {
             if (OpMethodMap.ContainsKey(clrName))

src/runtime/opshelper.cs

@@ -38,7 +38,7 @@ namespace Python.Runtime
     internal class OpsAttribute: Attribute { }
 
     [Ops]
-    internal static class EnumOps<T> where T : Enum
+    internal static class FlagEnumOps<T> where T : Enum
     {
         static readonly Func<T, T, T> and = BinaryOp(Expression.And);
         static readonly Func<T, T, T> or = BinaryOp(Expression.Or);
@@ -74,4 +74,16 @@ namespace Python.Runtime
             });
         }
     }
+
+    [Ops]
+    internal static class EnumOps<T> where T : Enum
+    {
+        [ForbidPythonThreads]
+#pragma warning disable IDE1006 // Naming Styles - must match Python
+        public static PyInt __int__(T value)
+#pragma warning restore IDE1006 // Naming Styles
+            => typeof(T).GetEnumUnderlyingType() == typeof(UInt64)
+            ? new PyInt(Convert.ToUInt64(value))
+            : new PyInt(Convert.ToInt64(value));
+    }
 }

src/testing/enumtest.cs

@@ -72,7 +72,9 @@ namespace Python.Test
         Two,
         Three,
         Four,
-        Five
+        Five,
+        Max = long.MaxValue,
+        Min = long.MinValue,
     }
 
     public enum ULongEnum : ulong
@@ -82,7 +84,8 @@ namespace Python.Test
         Two,
         Three,
         Four,
-        Five
+        Five,
+        Max = ulong.MaxValue,
     }
 
     [Flags]

tests/test_enum.py

@@ -87,6 +87,15 @@ def test_ulong_enum():
     assert Test.ULongEnum.Two == Test.ULongEnum(2)
 
 
+def test_long_enum_to_int():
+    assert int(Test.LongEnum.Max) == 9223372036854775807
+    assert int(Test.LongEnum.Min) == -9223372036854775808
+
+
+def test_ulong_enum_to_int():
+    assert int(Test.ULongEnum.Max) == 18446744073709551615
+
+
 def test_instantiate_enum_fails():
     """Test that instantiation of an enum class fails."""
     from System import DayOfWeek