Remove redundant flags enum values.

Author: AndriySvyryd

src/CSharpScriptSerializer/EnumCSScriptSerializer.cs

@@ -21,25 +21,24 @@ public override ExpressionSyntax GetCreation(object obj)
                 : GetSimpleValue(name);
         }
 
-        protected virtual ExpressionSyntax GetCompositeValue(Enum obj)
+        protected virtual ExpressionSyntax GetCompositeValue(Enum flags)
         {
-            var simpleValues = new List<ExpressionSyntax>();
-            var defaultValue = Enum.ToObject(Type, value: 0);
-            foreach (Enum currValue in Enum.GetValues(Type))
+            var simpleValues = new HashSet<Enum>(flags.GetFlags());
+            foreach (var currentValue in simpleValues.ToList())
             {
-                if (currValue.Equals(defaultValue))
+                var decomposedValues = currentValue.GetFlags();
+                if (decomposedValues.Count > 1)
                 {
-                    continue;
-                }
-
-                if (obj.HasFlag(currValue))
-                {
-                    simpleValues.Add(GetSimpleValue(Enum.GetName(Type, currValue)));
+                    simpleValues.ExceptWith(decomposedValues.Where(v => !Equals(v, currentValue)));
                 }
             }
 
-            return simpleValues.Aggregate((previous, current) =>
-                SyntaxFactory.BinaryExpression(SyntaxKind.BitwiseOrExpression, previous, current));
+            return simpleValues.Aggregate((ExpressionSyntax) null,
+                (previous, current) =>
+                    previous == null
+                        ? GetSimpleValue(Enum.GetName(Type, current))
+                        : SyntaxFactory.BinaryExpression(
+                            SyntaxKind.BitwiseOrExpression, previous, GetSimpleValue(Enum.GetName(Type, current))));
         }
 
         protected virtual ExpressionSyntax GetSimpleValue(string name)

src/CSharpScriptSerializer/Extensions.cs

@@ -5,20 +5,21 @@ namespace CSharpScriptSerialization
 {
     internal static class Extensions
     {
-        internal static IEnumerable<T> GetFlags<T>(this T flags)
+        internal static IReadOnlyCollection<Enum> GetFlags(this Enum flags)
         {
-            var values = new List<T>();
-            var defaultValue = Enum.ToObject(typeof(T), value: 0);
-            foreach (Enum currValue in Enum.GetValues(typeof(T)))
+            var values = new List<Enum>();
+            var type = flags.GetType();
+            var defaultValue = Enum.ToObject(type, value: 0);
+            foreach (Enum currValue in Enum.GetValues(type))
             {
                 if (currValue.Equals(defaultValue))
                 {
                     continue;
                 }
 
-                if (((Enum)(object)flags).HasFlag(currValue))
+                if (flags.HasFlag(currValue))
                 {
-                    values.Add((T)(object)currValue);
+                    values.Add(currValue);
                 }
             }
 

test/CSharpScriptSerializer.Tests/RoundTrippingTest.cs

@@ -148,7 +148,21 @@ public enum FlagsEnum
             Default = 0,
             FirstFlag = 1 << 0,
             SecondFlag = 1 << 1,
-            ThirdFlag = 1 << 2
+            ThirdFlag = 1 << 2,
+            SecondAndThird = SecondFlag | ThirdFlag,
+            FourthFlag = 1 << 3
+        }
+
+        [Fact]
+        public void Combined_flag_enum()
+        {
+            var input = FlagsEnum.FirstFlag| FlagsEnum.SecondAndThird;
+            var script = CSScriptSerializer.Serialize(input);
+            var output = CSScriptSerializer.Deserialize<FlagsEnum>(script);
+
+            Assert.Equal(input, output);
+            Assert.Equal(typeof(RoundtrippingTest).Name + "." + typeof(FlagsEnum).Name + "." + FlagsEnum.FirstFlag + " | "
+                + typeof(RoundtrippingTest).Name + "." + typeof(FlagsEnum).Name + "." + FlagsEnum.SecondAndThird, script);
         }
 
         [Fact]