Fix potential crash when deserializing Dictionary<T, U> where T is an enum

Tomlet.Tests/DeliberatelyIncorrectTestResources.resx

@@ -81,6 +81,15 @@ apple = "red"
 
 [fruit.apple]
 texture = "smooth"</value>
+    </data>
+    <data name="EnumKeyRedefinitionViaTableTestInput" xml:space="preserve">
+        <value>[Subnames]
+[Subnames.Value1]
+a = 'A'
+b = 'B'
+[Subnames.Value1]
+a = 'A'
+b = 'B'</value>
     </data>
     <data name="ReDefiningSubTableAsSubTableArrayTestInput" xml:space="preserve">
         <value># INVALID TOML DOC

Tomlet.Tests/EnumTests.cs

@@ -64,7 +64,16 @@ public void CanDeserializeEnumDictionary()
         var expected = new Dictionary<TestEnum, int> {{TestEnum.Value1, 1}, {TestEnum.Value2, 2}, {TestEnum.Value3, 3}};
         Assert.Equal(expected, result);
     }
-
+
+    [Fact]
+    public void CanIgnoreInvalidEnumDictionaryKeys()
+    {
+        var toml = "Value1 = 1\nValue2 = 2\nValue3 = 3\nValue4 = 4\nValue5 = 5\nValue6 = 6\n";
+        var result = TomletMain.To<Dictionary<TestEnum, int>>(toml, new TomlSerializerOptions { IgnoreInvalidEnumValues = true });
+        var expected = new Dictionary<TestEnum, int> {{TestEnum.Value1, 1}, {TestEnum.Value2, 2}, {TestEnum.Value3, 3}};
+        Assert.Equal(expected, result);
+    }
+
     [Fact]
     public void CanDeserializeEnumDictionaryWithFields()
     {

Tomlet.Tests/ExceptionTests.cs

@@ -109,6 +109,10 @@ public void ReDefiningASubTableAsASubTableArrayThrowsAnException() =>
     public void RedefiningAKeyAsATableNameThrowsAnException() => 
         AssertThrows<TomlKeyRedefinitionException>(() => GetDocument(DeliberatelyIncorrectTestResources.KeyRedefinitionViaTableTestInput));
 
+    [Fact]
+    public void RedefiningAnEnumKeyAsATableEntryThrowsAnException() => 
+        AssertThrows<TomlTableRedefinitionException>(() => GetDocument(DeliberatelyIncorrectTestResources.EnumKeyRedefinitionViaTableTestInput));
+
     [Fact]
     public void DefiningATableArrayWithTheSameNameAsATableThrowsAnException() => 
         AssertThrows<TomlTableArrayAlreadyExistsAsNonArrayException>(() => GetDocument(DeliberatelyIncorrectTestResources.DefiningAsArrayWhenAlreadyTableTestInput));

Tomlet/TomlSerializationMethods.cs

@@ -388,28 +388,32 @@ private static Deserialize<Dictionary<TKey, TValue>> PrimitiveKeyedDictionaryDes
             if (value is not TomlTable table)
                 throw new TomlTypeMismatchException(typeof(TomlTable), value.GetType(), typeof(Dictionary<TKey, TValue>));
 
-            return table.Entries.ToDictionary(
-                entry =>
+            return table.Entries
+                .Where(entry =>
                 {
-                    if (!type.IsEnum)
-                    {
-                        return (TKey)(entry.Key as IConvertible).ToType(typeof(TKey), CultureInfo.InvariantCulture);
-                    }
+                    if (!type.IsEnum || !options.IgnoreInvalidEnumValues)
+                        return true;
 
                     try
                     {
-                        return (TKey)Enum.Parse(type, entry.Key, true);
+                        _ = Enum.Parse(type, entry.Key, true);
+                        return true;
                     }
                     catch (ArgumentException)
                     {
-                        if (options.IgnoreInvalidEnumValues)
-                            return (TKey)Enum.GetValues(type).GetValue(0)!;
-
-                        throw new TomlEnumParseException(entry.Key, typeof(TKey));
+                        return false;
                     }
+                })
+                .ToDictionary(entry =>
+                {
+                    if (!type.IsEnum)
+                    {
+                        return (TKey)(entry.Key as IConvertible).ToType(typeof(TKey), CultureInfo.InvariantCulture);
+                    }
+
+                    return (TKey)Enum.Parse(type, entry.Key, true);
                 },
-                entry => (TValue)valueDeserializer(entry.Value)
-            );
+                entry => (TValue)valueDeserializer(entry.Value));
         };
     }
 

Tomlet/TomlSerializerOptions.cs

@@ -17,5 +17,8 @@ public class TomlSerializerOptions
     /// <summary>
     /// When set to true, the deserializer will ignore invalid enum values (and they will be implicitly left at their default value). When set to false, an exception will be thrown if the enum value is not found.
     /// </summary>
+    /// <remarks>
+    /// When deserializing dictionaries with enums as keys, invalid enum values will be skipped.
+    /// </remarks>
     public bool IgnoreInvalidEnumValues { get; set; } = false;
 }