chore: Enable Nullable on YamlSerialization project

src/Docfx.YamlSerialization/Docfx.YamlSerialization.csproj

@@ -1,4 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
   <ItemGroup>
     <PackageReference Include="YamlDotNet" />
   </ItemGroup>

src/Docfx.YamlSerialization/ExtensibleMemberAttribute.cs

@@ -9,12 +9,12 @@ public sealed class ExtensibleMemberAttribute : Attribute
     public string Prefix { get; }
 
     public ExtensibleMemberAttribute()
-        : this(null)
+        : this(string.Empty)
     {
     }
 
     public ExtensibleMemberAttribute(string prefix)
     {
-        Prefix = prefix ?? string.Empty;
+        Prefix = prefix;
     }
 }

src/Docfx.YamlSerialization/Helpers/ReflectionUtility.cs

@@ -5,7 +5,7 @@ namespace Docfx.YamlSerialization.Helpers;
 
 internal static class ReflectionUtility
 {
-    public static Type GetImplementedGenericInterface(Type type, Type genericInterfaceType)
+    public static Type? GetImplementedGenericInterface(Type type, Type genericInterfaceType)
     {
         foreach (var interfaceType in GetImplementedInterfaces(type))
         {

src/Docfx.YamlSerialization/NodeDeserializers/EmitArrayNodeDeserializer.cs

@@ -13,11 +13,11 @@ namespace Docfx.YamlSerialization.NodeDeserializers;
 public class EmitArrayNodeDeserializer : INodeDeserializer
 {
     private static readonly MethodInfo DeserializeHelperMethod =
-        typeof(EmitArrayNodeDeserializer).GetMethod(nameof(DeserializeHelper));
-    private static readonly ConcurrentDictionary<Type, Func<IParser, Type, Func<IParser, Type, object>, object>> _funcCache =
+        typeof(EmitArrayNodeDeserializer).GetMethod(nameof(DeserializeHelper))!;
+    private static readonly ConcurrentDictionary<Type, Func<IParser, Type, Func<IParser, Type, object?>, object?>> _funcCache =
         new();
 
-    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
+    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, out object? value)
     {
         if (!expectedType.IsArray)
         {
@@ -31,22 +31,22 @@ bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IPars
     }
 
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public static TItem[] DeserializeHelper<TItem>(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer)
+    public static TItem[] DeserializeHelper<TItem>(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer)
     {
         var items = new List<TItem>();
         EmitGenericCollectionNodeDeserializer.DeserializeHelper(reader, expectedType, nestedObjectDeserializer, items);
         return items.ToArray();
     }
 
-    private static Func<IParser, Type, Func<IParser, Type, object>, object> AddItem(Type expectedType)
+    private static Func<IParser, Type, Func<IParser, Type, object?>, object?> AddItem(Type expectedType)
     {
         var dm = new DynamicMethod(string.Empty, typeof(object), [typeof(IParser), typeof(Type), typeof(Func<IParser, Type, object>)]);
         var il = dm.GetILGenerator();
         il.Emit(OpCodes.Ldarg_0);
         il.Emit(OpCodes.Ldarg_1);
         il.Emit(OpCodes.Ldarg_2);
-        il.Emit(OpCodes.Call, DeserializeHelperMethod.MakeGenericMethod(expectedType.GetElementType()));
+        il.Emit(OpCodes.Call, DeserializeHelperMethod.MakeGenericMethod(expectedType.GetElementType()!));
         il.Emit(OpCodes.Ret);
-        return (Func<IParser, Type, Func<IParser, Type, object>, object>)dm.CreateDelegate(typeof(Func<IParser, Type, Func<IParser, Type, object>, object>));
+        return (Func<IParser, Type, Func<IParser, Type, object?>, object?>)dm.CreateDelegate(typeof(Func<IParser, Type, Func<IParser, Type, object?>, object?>));
     }
 }

src/Docfx.YamlSerialization/NodeDeserializers/EmitGenericCollectionNodeDeserializer.cs

@@ -17,21 +17,21 @@ namespace Docfx.YamlSerialization.NodeDeserializers;
 public class EmitGenericCollectionNodeDeserializer : INodeDeserializer
 {
     private static readonly MethodInfo DeserializeHelperMethod =
-        typeof(EmitGenericCollectionNodeDeserializer).GetMethod(nameof(DeserializeHelper));
+        typeof(EmitGenericCollectionNodeDeserializer).GetMethod(nameof(DeserializeHelper))!;
     private readonly IObjectFactory _objectFactory;
-    private readonly Dictionary<Type, Type> _gpCache =
+    private readonly Dictionary<Type, Type?> _gpCache =
         new();
-    private readonly Dictionary<Type, Action<IParser, Type, Func<IParser, Type, object>, object>> _actionCache =
+    private readonly Dictionary<Type, Action<IParser, Type, Func<IParser, Type, object?>, object?>> _actionCache =
         new();
 
     public EmitGenericCollectionNodeDeserializer(IObjectFactory objectFactory)
     {
         _objectFactory = objectFactory;
     }
 
-    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
+    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, out object? value)
     {
-        if (!_gpCache.TryGetValue(expectedType, out Type gp))
+        if (!_gpCache.TryGetValue(expectedType, out var gp))
         {
             var collectionType = ReflectionUtility.GetImplementedGenericInterface(expectedType, typeof(ICollection<>));
             if (collectionType != null)
@@ -66,7 +66,7 @@ bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IPars
             il.Emit(OpCodes.Castclass, typeof(ICollection<>).MakeGenericType(gp));
             il.Emit(OpCodes.Call, DeserializeHelperMethod.MakeGenericMethod(gp));
             il.Emit(OpCodes.Ret);
-            action = (Action<IParser, Type, Func<IParser, Type, object>, object>)dm.CreateDelegate(typeof(Action<IParser, Type, Func<IParser, Type, object>, object>));
+            action = (Action<IParser, Type, Func<IParser, Type, object?>, object?>)dm.CreateDelegate(typeof(Action<IParser, Type, Func<IParser, Type, object?>, object?>));
             _actionCache[gp] = action;
         }
 
@@ -75,13 +75,11 @@ bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IPars
     }
 
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public static void DeserializeHelper<TItem>(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, ICollection<TItem> result)
+    public static void DeserializeHelper<TItem>(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, ICollection<TItem> result)
     {
         reader.Consume<SequenceStart>();
         while (!reader.Accept<SequenceEnd>(out _))
         {
-            var current = reader.Current;
-
             var value = nestedObjectDeserializer(reader, typeof(TItem));
             if (value is not IValuePromise promise)
             {
@@ -90,11 +88,12 @@ public static void DeserializeHelper<TItem>(IParser reader, Type expectedType, F
             else if (result is IList<TItem> list)
             {
                 var index = list.Count;
-                result.Add(default);
+                result.Add(default!);
                 promise.ValueAvailable += v => list[index] = TypeConverter.ChangeType<TItem>(v, NullNamingConvention.Instance);
             }
             else
             {
+                var current = reader.Current!;
                 throw new ForwardAnchorNotSupportedException(
                     current.Start,
                     current.End,

src/Docfx.YamlSerialization/NodeDeserializers/EmitGenericDictionaryNodeDeserializer.cs

@@ -14,21 +14,21 @@ namespace Docfx.YamlSerialization.NodeDeserializers;
 public class EmitGenericDictionaryNodeDeserializer : INodeDeserializer
 {
     private static readonly MethodInfo DeserializeHelperMethod =
-        typeof(EmitGenericDictionaryNodeDeserializer).GetMethod(nameof(DeserializeHelper));
+        typeof(EmitGenericDictionaryNodeDeserializer).GetMethod(nameof(DeserializeHelper))!;
     private readonly IObjectFactory _objectFactory;
-    private readonly Dictionary<Type, Type[]> _gpCache =
+    private readonly Dictionary<Type, Type[]?> _gpCache =
         new();
-    private readonly Dictionary<Tuple<Type, Type>, Action<IParser, Type, Func<IParser, Type, object>, object>> _actionCache =
+    private readonly Dictionary<Tuple<Type, Type>, Action<IParser, Type, Func<IParser, Type, object?>, object?>> _actionCache =
         new();
 
     public EmitGenericDictionaryNodeDeserializer(IObjectFactory objectFactory)
     {
         _objectFactory = objectFactory;
     }
 
-    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
+    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, out object? value)
     {
-        if (!_gpCache.TryGetValue(expectedType, out Type[] gp))
+        if (!_gpCache.TryGetValue(expectedType, out var gp))
         {
             var dictionaryType = ReflectionUtility.GetImplementedGenericInterface(expectedType, typeof(IDictionary<,>));
             if (dictionaryType != null)
@@ -67,7 +67,7 @@ bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IPars
             il.Emit(OpCodes.Castclass, typeof(IDictionary<,>).MakeGenericType(gp));
             il.Emit(OpCodes.Call, DeserializeHelperMethod.MakeGenericMethod(gp));
             il.Emit(OpCodes.Ret);
-            action = (Action<IParser, Type, Func<IParser, Type, object>, object>)dm.CreateDelegate(typeof(Action<IParser, Type, Func<IParser, Type, object>, object>));
+            action = (Action<IParser, Type, Func<IParser, Type, object?>, object?>)dm.CreateDelegate(typeof(Action<IParser, Type, Func<IParser, Type, object?>, object?>));
             _actionCache[cacheKey] = action;
         }
         action(reader, expectedType, nestedObjectDeserializer, value);
@@ -78,7 +78,7 @@ bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IPars
     }
 
     [EditorBrowsable(EditorBrowsableState.Never)]
-    public static void DeserializeHelper<TKey, TValue>(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, IDictionary<TKey, TValue> result)
+    public static void DeserializeHelper<TKey, TValue>(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, IDictionary<TKey, TValue> result)
     {
         while (!reader.Accept<MappingEnd>(out _))
         {
@@ -92,20 +92,20 @@ public static void DeserializeHelper<TKey, TValue>(IParser reader, Type expected
                 if (valuePromise == null)
                 {
                     // Happy path: both key and value are known
-                    result[(TKey)key] = (TValue)value;
+                    result[(TKey)key!] = (TValue)value!;
                 }
                 else
                 {
                     // Key is known, value is pending
-                    valuePromise.ValueAvailable += v => result[(TKey)key] = (TValue)v;
+                    valuePromise.ValueAvailable += v => result[(TKey)key!] = (TValue)v!;
                 }
             }
             else
             {
                 if (valuePromise == null)
                 {
                     // Key is pending, value is known
-                    keyPromise.ValueAvailable += v => result[(TKey)v] = (TValue)value;
+                    keyPromise.ValueAvailable += v => result[(TKey)v!] = (TValue)value!;
                 }
                 else
                 {
@@ -116,7 +116,7 @@ public static void DeserializeHelper<TKey, TValue>(IParser reader, Type expected
                     {
                         if (hasFirstPart)
                         {
-                            result[(TKey)v] = (TValue)value;
+                            result[(TKey)v!] = (TValue)value!;
                         }
                         else
                         {
@@ -129,7 +129,7 @@ public static void DeserializeHelper<TKey, TValue>(IParser reader, Type expected
                     {
                         if (hasFirstPart)
                         {
-                            result[(TKey)key] = (TValue)v;
+                            result[(TKey)key] = (TValue)v!;
                         }
                         else
                         {

src/Docfx.YamlSerialization/NodeDeserializers/ExtensibleObjectNodeDeserializer.cs

@@ -22,7 +22,7 @@ public ExtensibleObjectNodeDeserializer(IObjectFactory objectFactory, ITypeInspe
         _ignoreUnmatched = ignoreUnmatched;
     }
 
-    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object> nestedObjectDeserializer, out object value)
+    bool INodeDeserializer.Deserialize(IParser reader, Type expectedType, Func<IParser, Type, object?> nestedObjectDeserializer, out object? value)
     {
         if (!reader.TryConsume<MappingStart>(out _))
         {

src/Docfx.YamlSerialization/NodeTypeResolvers/ScalarYamlNodeTypeResolver.cs

@@ -9,7 +9,7 @@ namespace Docfx.YamlSerialization.NodeTypeResolvers;
 
 internal sealed class ScalarYamlNodeTypeResolver : INodeTypeResolver
 {
-    bool INodeTypeResolver.Resolve(NodeEvent nodeEvent, ref Type currentType)
+    bool INodeTypeResolver.Resolve(NodeEvent? nodeEvent, ref Type currentType)
     {
         if (currentType == typeof(string) || currentType == typeof(object))
         {

src/Docfx.YamlSerialization/ObjectDescriptors/BetterObjectDescriptor.cs

@@ -9,21 +9,21 @@ namespace Docfx.YamlSerialization.ObjectDescriptors;
 
 public class BetterObjectDescriptor : IObjectDescriptor
 {
-    public BetterObjectDescriptor(object value, Type type, Type staticType)
+    public BetterObjectDescriptor(object? value, Type type, Type staticType)
         : this(value, type, staticType, ScalarStyle.Any)
     {
     }
 
-    public BetterObjectDescriptor(object value, Type type, Type staticType, ScalarStyle scalarStyle)
+    public BetterObjectDescriptor(object? value, Type type, Type staticType, ScalarStyle scalarStyle)
     {
         Value = value;
         Type = type;
         StaticType = staticType;
         ScalarStyle = scalarStyle == ScalarStyle.Any && NeedQuote(value) ? ScalarStyle.DoubleQuoted : scalarStyle;
 
-        static bool NeedQuote(object val)
+        static bool NeedQuote(object? val)
         {
-            if (val is not string s)
+            if (val is not string s || s == null)
                 return false;
 
             return Regexes.BooleanLike().IsMatch(s)
@@ -42,5 +42,5 @@ static bool NeedQuote(object val)
 
     public Type Type { get; }
 
-    public object Value { get; }
+    public object? Value { get; }
 }

src/Docfx.YamlSerialization/ObjectFactories/DefaultEmitObjectFactory.cs

@@ -15,10 +15,10 @@ public class DefaultEmitObjectFactory : ObjectFactoryBase
 
     public override object Create(Type type)
     {
-        if (!_cache.TryGetValue(type, out Func<object> func))
+        if (!_cache.TryGetValue(type, out var func))
         {
             var realType = type;
-            if (type is {IsInterface: true, IsGenericType: true})
+            if (type is { IsInterface: true, IsGenericType: true })
             {
                 var def = type.GetGenericTypeDefinition();
                 var args = type.GetGenericArguments();
@@ -46,7 +46,12 @@ public override object Create(Type type)
             {
                 func = CreateValueTypeFactory(type);
             }
-            _cache[type] = func;
+            else
+            {
+                throw new InvalidOperationException($"Failed to gets type instance create func for type: {type.FullName}.");
+            }
+
+            _cache[type] = func!;
         }
         return func();
     }
@@ -56,7 +61,7 @@ private static Func<object> CreateReferenceTypeFactory(ConstructorInfo ctor)
         var dm = new DynamicMethod(string.Empty, typeof(object), EmptyTypes);
         var il = dm.GetILGenerator();
         il.Emit(OpCodes.Newobj, ctor);
-        if (ctor.DeclaringType.IsValueType)
+        if (ctor.DeclaringType!.IsValueType)
         {
             il.Emit(OpCodes.Box, ctor.DeclaringType);
         }