Add better constructor support for deserialization

Tomlet.Tests/ClassDeserializationTests.cs

@@ -54,6 +54,14 @@ public void SimpleRecordDeserializationWorks()
             Assert.Equal(new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc), type.MyDateTime);
         }
 
+        [Fact]
+        public void ClassWithParameterlessConstructorDeserializationWorks()
+        {
+            var type = TomletMain.To<ClassWithParameterlessConstructor>(TestResources.SimplePrimitiveDeserializationTestInput);
+
+            Assert.Equal("Hello, world!", type.MyString);
+        }
+
         [Fact]
         public void AnArrayOfEmptyStringsCanBeDeserialized()
         {
@@ -75,5 +83,23 @@ public void AttemptingToDeserializeADocumentWithAnIncorrectlyTypedFieldThrows()
             var msg = $"While deserializing an object of type {typeof(SimplePrimitiveTestClass).FullName}, found field MyFloat expecting a type of Double, but value in TOML was of type String";
             Assert.Equal(msg, ex.Message);
         }
+
+        [Fact]
+        public void ShouldOverrideDefaultConstructorsValues()
+        {
+            var options = new TomlSerializerOptions { OverrideConstructorValues = true };
+            var type = TomletMain.To<ClassWithValuesSetOnConstructor>(TestResources.SimplePrimitiveDeserializationTestInput, options);
+
+            Assert.Equal("Hello, world!", type.MyString);
+        }
+
+        [Fact]
+        public void ShouldNotOverrideDefaultConstructorsValues()
+        {
+            var options = new TomlSerializerOptions { OverrideConstructorValues = false };
+            var type = TomletMain.To<ClassWithValuesSetOnConstructor>(TestResources.SimplePrimitiveDeserializationTestInput, options);
+
+            Assert.Equal("Modified on constructor!", type.MyString);
+        }
     }
 }

Tomlet.Tests/ClassWithValuesSetOnConstructor.cs

@@ -0,0 +1,11 @@
+namespace Tomlet.Tests;
+
+public class ClassWithValuesSetOnConstructor
+{
+    public ClassWithValuesSetOnConstructor(string myString)
+    {
+        MyString = "Modified on constructor!";
+    }
+
+    public string MyString { get; set; }
+}

Tomlet.Tests/ExceptionTests.cs

@@ -190,6 +190,14 @@ public void UnicodeControlCharsThrowAnException() =>
     [Fact]
     public void UnInstantiableObjectsThrow() => 
         AssertThrows<TomlInstantiationException>(() => TomletMain.To<IConvertible>(""));
+
+    [Fact]
+    public void MultipleParameterizedConstructorsThrow() =>
+        AssertThrows<TomlInstantiationException>(() => TomletMain.To<ClassWithMultipleParameterizedConstructors>(""));
+
+    [Fact]
+    public void AbstractClassDeserializationThrows() =>
+        AssertThrows<TomlInstantiationException>(() => TomletMain.To<AbstractClass>(""));
 
     [Fact]
     public void MismatchingTypesInPrimitiveMappingThrows() => 

Tomlet.Tests/ObjectToStringTests.cs

@@ -77,34 +77,23 @@ public void SerializingSimplePropertyClassAndDeserializingAgainGivesEquivalentOb
         [Fact]
         public void SerializingSimpleTestRecordToTomlStringWorks()
         {
-            var testObject = new SimpleTestRecord
-            {
-                MyBool = true,
-                MyFloat = 420.69f,
-                MyString = "Hello, world!",
-                MyDateTime = new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc)
-            };
-
+            var testObject = new SimpleTestRecord("Hello, world!", 420.69f, true,
+                new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc));
             var serializedForm = TomletMain.TomlStringFrom(testObject);
-
+        
             Assert.Equal("MyString = \"Hello, world!\"\nMyFloat = 420.69000244140625\nMyBool = true\nMyDateTime = 1970-01-01T07:00:00", serializedForm.Trim());
         }
 
         [Fact]
         public void SerializingSimpleTestRecordAndDeserializingAgainGivesEquivalentObject()
         {
-            var testObject = new SimpleTestRecord
-            {
-                MyBool = true,
-                MyFloat = 420.69f,
-                MyString = "Hello, world!",
-                MyDateTime = new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc)
-            };
+            var testObject = new SimpleTestRecord("Hello, world!", 420.69f, true,
+                new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc));
 
             var serializedForm = TomletMain.TomlStringFrom(testObject);
-
+        
             var deserializedAgain = TomletMain.To<SimpleTestRecord>(serializedForm);
-
+        
             Assert.Equal(testObject, deserializedAgain);
         }
 
@@ -120,7 +109,7 @@ public void SerializingAnEmptyObjectGivesAnEmptyString()
         public void AttemptingToDirectlySerializeNullThrows()
         {
             //We need to use a type of T that actually has something to serialize
-            Assert.Throws<ArgumentNullException>(() => TomletMain.DocumentFrom(typeof(SimplePrimitiveTestClass), null!));
+            Assert.Throws<ArgumentNullException>(() => TomletMain.DocumentFrom(typeof(SimplePrimitiveTestClass), null!, null));
         }
     }
 }

Tomlet.Tests/ObjectToTomlDocTests.cs

@@ -66,20 +66,15 @@ public void SimplePropertyClassToTomlDocWorks()
             Assert.Equal("Hello, world!", tomlDoc.GetString("MyString"));
             Assert.Equal("1970-01-01T07:00:00", tomlDoc.GetValue("MyDateTime").StringValue);
         }
-
+        
         [Fact]
         public void SimpleTestRecordToTomlDocWorks()
         {
-            var testObject = new SimpleTestRecord
-            {
-                MyBool = true,
-                MyFloat = 420.69f,
-                MyString = "Hello, world!",
-                MyDateTime = new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc)
-            };
+            var testObject = new SimpleTestRecord("Hello, world!", 420.69f, true,
+                new DateTime(1970, 1, 1, 7, 0, 0, DateTimeKind.Utc));
 
             var tomlDoc = TomletMain.DocumentFrom(testObject);
-
+        
             Assert.Equal(4, tomlDoc.Entries.Count);
             Assert.True(tomlDoc.GetBoolean("MyBool"));
             Assert.True(Math.Abs(tomlDoc.GetFloat("MyFloat") - 420.69) < 0.01);

Tomlet.Tests/TestModelClasses/AbstractClass.cs

@@ -0,0 +1,6 @@
+namespace Tomlet.Tests.TestModelClasses;
+
+public abstract class AbstractClass
+{
+
+}

Tomlet.Tests/TestModelClasses/ClassWithMultipleParameterizedConstructors.cs

@@ -0,0 +1,16 @@
+namespace Tomlet.Tests.TestModelClasses;
+
+public class ClassWithMultipleParameterizedConstructors
+{
+    public ClassWithMultipleParameterizedConstructors(string myString)
+    {
+        MyString = myString;
+    }
+
+    public ClassWithMultipleParameterizedConstructors(string myString, int age)
+    {
+        MyString = myString;
+    }
+
+    public string MyString { get; set; }
+}

Tomlet.Tests/TestModelClasses/ClassWithParameterlessConstructor.cs

@@ -0,0 +1,9 @@
+namespace Tomlet.Tests.TestModelClasses;
+
+public class ClassWithParameterlessConstructor : ClassWithMultipleParameterizedConstructors
+{
+    public ClassWithParameterlessConstructor() : base(string.Empty, int.MinValue)
+    {
+
+    }
+}

Tomlet.Tests/TestModelClasses/SimpleTestRecord.cs

@@ -1,12 +1,5 @@
 using System;
 
-namespace Tomlet.Tests.TestModelClasses
-{
-    public record SimpleTestRecord
-    {
-        public string MyString { get; init; }
-        public float MyFloat { get; init; }
-        public bool MyBool { get; init; }
-        public DateTime MyDateTime { get; init; }
-    }
-}
+namespace Tomlet.Tests.TestModelClasses;
+
+public record SimpleTestRecord(string MyString, float MyFloat, bool MyBool, DateTime MyDateTime);

Tomlet/Exceptions/TomlInstantiationException.cs

@@ -1,16 +1,8 @@
-using System;
-
-namespace Tomlet.Exceptions
+namespace Tomlet.Exceptions
 {
     public class TomlInstantiationException : TomlException
     {
-        private readonly Type _type;
-
-        public TomlInstantiationException(Type type)
-        {
-            _type = type;
-        }
-
-        public override string Message => $"Could not find a no-argument constructor for type {_type.FullName}";
+        public override string Message =>
+            "Deserialization of types without a parameterless constructor or a singular parameterized constructor is not supported.";
     }
 }

Tomlet/Exceptions/TomlParameterTypeMismatchException.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Reflection;
+
+namespace Tomlet.Exceptions
+{
+    public class TomlParameterTypeMismatchException : TomlTypeMismatchException
+    {
+        private readonly Type _typeBeingInstantiated;
+        private readonly ParameterInfo _paramBeingDeserialized;
+
+        public TomlParameterTypeMismatchException(Type typeBeingInstantiated, ParameterInfo paramBeingDeserialized, TomlTypeMismatchException cause) : base(cause.ExpectedType, cause.ActualType, paramBeingDeserialized.ParameterType)
+        {
+            _typeBeingInstantiated = typeBeingInstantiated;
+            _paramBeingDeserialized = paramBeingDeserialized;
+        }
+
+        public override string Message => $"While deserializing an object of type {_typeBeingInstantiated}, found parameter {_paramBeingDeserialized.Name} expecting a type of {ExpectedTypeName}, but value in TOML was of type {ActualTypeName}";
+    }
+}

Tomlet/Extensions.cs → Tomlet/Extensions/GenericExtensions.cs

@@ -6,9 +6,9 @@
 using System.Text;
 using Tomlet.Exceptions;
 
-namespace Tomlet
+namespace Tomlet.Extensions
 {
-    internal static class Extensions
+    internal static class GenericExtensions
     {
         private static readonly HashSet<int> IllegalChars = new()
         {

Tomlet/Extensions/ReflectionExtensions.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Linq;
+using System.Reflection;
+
+namespace Tomlet.Extensions
+{
+    internal static class ReflectionExtensions
+    {
+        internal static bool TryGetBestMatchConstructor(this Type type, out ConstructorInfo? bestMatchConstructor)
+        {
+            var constructors = type.GetConstructors(BindingFlags.Public | BindingFlags.Instance);
+            if (constructors.Length == 0)
+            {
+                bestMatchConstructor = null;
+                return false;
+            }
+
+            var parameterlessConstructor = constructors.FirstOrDefault(c => c.GetParameters().Length == 0);
+            if (parameterlessConstructor != null)
+            {
+                bestMatchConstructor = parameterlessConstructor;
+                return true;
+            }
+
+            var parameterizedConstructors = constructors.Where(c => c.GetParameters().Length > 0).ToArray();
+            if (parameterizedConstructors.Length > 1)
+            {
+                bestMatchConstructor = null;
+                return false;
+            }
+
+            bestMatchConstructor = parameterizedConstructors.Single();
+            return true;
+        }
+    }
+}

Tomlet/Extensions/StringExtensions.cs

@@ -0,0 +1,24 @@
+using System.Text;
+
+namespace Tomlet.Extensions
+{
+    internal static class StringExtensions
+    {
+        internal static string ToPascalCase(this string str)
+        {
+            var sb = new StringBuilder(str.Length);
+
+            if (str.Length > 0)
+            {
+                sb.Append(char.ToUpper(str[0]));
+            }
+
+            for (var i = 1; i < str.Length; i++)
+            {
+                sb.Append(char.IsWhiteSpace(str[i - 1]) ? char.ToUpper(str[i]) : str[i]);
+            }
+
+            return sb.ToString();
+        }
+    }
+}

Tomlet/Models/TomlString.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Tomlet.Extensions;
 
 namespace Tomlet.Models
 {

Tomlet/Models/TomlTable.cs

@@ -1,10 +1,11 @@
-using System;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text;
 using Tomlet.Exceptions;
+using Tomlet.Extensions;
 
 namespace Tomlet.Models
 {