refactor: enable nullable ref type checking

Directory.Build.props

@@ -32,7 +32,7 @@
     <WarningsNotAsErrors>$(WarningsNotAsErrors);1591</WarningsNotAsErrors>
     <LangVersion>9.0</LangVersion>
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
-    <Nullable>annotations</Nullable>
+    <Nullable>enable</Nullable>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)src\StrongName.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
 

src/CommandLineUtils/Attributes/AllowedValuesAttribute.cs

@@ -66,14 +66,14 @@ or StringComparison.InvariantCultureIgnoreCase
         }
 
         /// <inheritdoc />
-        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+        protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
         {
             if (value is string str && _allowedValues.Any(t => str.Equals(t, Comparer)))
             {
                 return ValidationResult.Success;
             }
 
-            return new ValidationResult(FormatErrorMessage(value as string));
+            return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
         }
     }
 }

src/CommandLineUtils/Attributes/FilePathExistsAttributeBase.cs

@@ -27,11 +27,11 @@ internal FilePathExistsAttributeBase(FilePathType filePathType)
         }
 
         /// <inheritdoc />
-        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+        protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
         {
             if (value is not string path || path.Length == 0 || path.IndexOfAny(Path.GetInvalidPathChars()) >= 0)
             {
-                return new ValidationResult(FormatErrorMessage(value as string));
+                return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
             }
 
             if (!Path.IsPathRooted(path)
@@ -50,7 +50,7 @@ protected override ValidationResult IsValid(object value, ValidationContext vali
                 return ValidationResult.Success;
             }
 
-            return new ValidationResult(FormatErrorMessage(value as string));
+            return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
         }
 
         private static string GetDefaultErrorMessage(FilePathType filePathType)

src/CommandLineUtils/Attributes/FilePathNotExistsAttributeBase.cs

@@ -27,11 +27,11 @@ internal FilePathNotExistsAttributeBase(FilePathType filePathType)
         }
 
         /// <inheritdoc />
-        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+        protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
         {
             if (value is not string path || path.Length == 0 || path.IndexOfAny(Path.GetInvalidPathChars()) >= 0)
             {
-                return new ValidationResult(FormatErrorMessage(value as string));
+                return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
             }
 
             if (!Path.IsPathRooted(path)
@@ -55,7 +55,7 @@ protected override ValidationResult IsValid(object value, ValidationContext vali
                 return ValidationResult.Success;
             }
 
-            return new ValidationResult(FormatErrorMessage(value as string));
+            return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
         }
 
         private static string GetDefaultErrorMessage(FilePathType filePathType)

src/CommandLineUtils/Attributes/LegalFilePathAttribute.cs

@@ -23,7 +23,7 @@ public LegalFilePathAttribute()
         }
 
         /// <inheritdoc />
-        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
+        protected override ValidationResult? IsValid(object? value, ValidationContext validationContext)
         {
             if (value is string path)
             {
@@ -37,7 +37,7 @@ protected override ValidationResult IsValid(object value, ValidationContext vali
                 }
             }
 
-            return new ValidationResult(FormatErrorMessage(value as string));
+            return new ValidationResult(FormatErrorMessage(value?.ToString() ?? string.Empty));
         }
     }
 }

src/CommandLineUtils/CommandArgument.cs

@@ -78,7 +78,7 @@ public IReadOnlyList<string?> Values
         /// <summary>
         /// Defines the underlying type of the argument for the help-text-generator
         /// </summary>
-        internal Type UnderlyingType { get; set; }
+        internal Type? UnderlyingType { get; set; }
 
         /// <summary>
         /// Try to add a value to this argument.

src/CommandLineUtils/CommandArgument{T}.cs

@@ -52,9 +52,9 @@ public IReadOnlyList<T> ParsedValues
                     ((IInternalCommandParamOfT)this).Parse(CultureInfo.CurrentCulture);
                 }
 
-                if (_parsedValues.Count == 0 && _hasDefaultValue)
+                if (_parsedValues.Count == 0 && _hasDefaultValue && DefaultValue != null)
                 {
-                    return new[] { DefaultValue };
+                    return new T[] { DefaultValue };
                 }
 
                 return _parsedValues;
@@ -85,7 +85,7 @@ void IInternalCommandParamOfT.Parse(CultureInfo culture)
             }
         }
 
-        void SetBaseDefaultValue(T value)
+        void SetBaseDefaultValue(T? value)
         {
             if (!ReflectionHelper.IsSpecialValueTupleType(typeof(T), out _))
             {

src/CommandLineUtils/CommandLineApplication.Validation.cs

@@ -32,7 +32,7 @@ public Func<ValidationResult, int> ValidationErrorHandler
         /// Validates arguments and options.
         /// </summary>
         /// <returns>The first validation result that is not <see cref="ValidationResult.Success"/> if there is an error.</returns>
-        public ValidationResult GetValidationResult()
+        public ValidationResult? GetValidationResult()
         {
             if (Parent != null)
             {

src/CommandLineUtils/CommandLineApplication.cs

@@ -863,7 +863,7 @@ public async Task<int> ExecuteAsync(string[] args, CancellationToken cancellatio
             }
 
             var validationResult = command.GetValidationResult();
-            if (validationResult != ValidationResult.Success)
+            if (validationResult != null)
             {
                 return command.ValidationErrorHandler(validationResult);
             }

src/CommandLineUtils/CommandLineApplication{T}.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using McMaster.Extensions.CommandLineUtils.Abstractions;
 using McMaster.Extensions.CommandLineUtils.Conventions;
 using McMaster.Extensions.CommandLineUtils.HelpText;
@@ -15,6 +16,7 @@ namespace McMaster.Extensions.CommandLineUtils
     public class CommandLineApplication<TModel> : CommandLineApplication, IModelAccessor
         where TModel : class
     {
+        [AllowNull] // this is initialized in common method called in all constructors
         private Lazy<TModel> _lazy;
         private Func<TModel> _modelFactory = DefaultModelFactory;
 

src/CommandLineUtils/CommandOption.cs

@@ -137,7 +137,7 @@ public IReadOnlyList<string?> Values
         /// <summary>
         /// Defines the underlying type of the option for the help-text-generator
         /// </summary>
-        internal Type UnderlyingType { get; set; }
+        internal Type? UnderlyingType { get; set; }
 
         /// <summary>
         /// A collection of validators that execute before invoking <see cref="CommandLineApplication.OnExecute(Func{int})"/>.

src/CommandLineUtils/CommandOption{T}.cs

@@ -53,7 +53,7 @@ public IReadOnlyList<T> ParsedValues
                     ((IInternalCommandParamOfT)this).Parse(CultureInfo.CurrentCulture);
                 }
 
-                if (_parsedValues.Count == 0 && _hasDefaultValue)
+                if (_parsedValues.Count == 0 && _hasDefaultValue && DefaultValue != null)
                 {
                     return new[] { DefaultValue };
                 }
@@ -86,7 +86,7 @@ void IInternalCommandParamOfT.Parse(CultureInfo culture)
             }
         }
 
-        private void SetBaseDefaultValue(T value)
+        private void SetBaseDefaultValue(T? value)
         {
             if (!ReflectionHelper.IsSpecialValueTupleType(typeof(T), out _))
             {

src/CommandLineUtils/Conventions/ExecuteMethodConvention.cs

@@ -35,8 +35,8 @@ private async Task<int> OnExecute(ConventionContext context, CancellationToken c
             MethodInfo? asyncMethod;
             try
             {
-                method = context.ModelType.GetMethod("OnExecute", binding);
-                asyncMethod = context.ModelType.GetMethod("OnExecuteAsync", binding);
+                method = context.ModelType?.GetMethod("OnExecute", binding);
+                asyncMethod = context.ModelType?.GetMethod("OnExecuteAsync", binding);
             }
             catch (AmbiguousMatchException ex)
             {
@@ -75,7 +75,7 @@ private async Task<int> OnExecute(ConventionContext context, CancellationToken c
             throw new InvalidOperationException(Strings.InvalidOnExecuteReturnType(method.Name));
         }
 
-        private async Task<int> InvokeAsync(MethodInfo method, object instance, object[] arguments)
+        private async Task<int> InvokeAsync(MethodInfo method, object instance, object?[] arguments)
         {
             try
             {
@@ -95,7 +95,7 @@ private async Task<int> InvokeAsync(MethodInfo method, object instance, object[]
             return 0;
         }
 
-        private int Invoke(MethodInfo method, object instance, object[] arguments)
+        private int Invoke(MethodInfo method, object instance, object?[] arguments)
         {
             try
             {

src/CommandLineUtils/Conventions/SubcommandAttributeConvention.cs

@@ -67,7 +67,7 @@ private static readonly MethodInfo s_addSubcommandMethod
         private void AddSubcommandImpl<TSubCommand>(ConventionContext context)
             where TSubCommand : class
         {
-            context.Application.Command<TSubCommand>(null, null);
+            context.Application.Command<TSubCommand>(null!, null!); // Hmm, should probably rethink this...
         }
     }
 }

src/CommandLineUtils/HelpText/DefaultHelpTextGenerator.cs

@@ -409,7 +409,7 @@ protected virtual string Format(CommandOption option)
             }
         }
 
-        private string[] ExtractNamesFromEnum(Type type)
+        private string[] ExtractNamesFromEnum(Type? type)
         {
             if (type == null)
             {

src/CommandLineUtils/Internal/CommandLineProcessor.cs

@@ -335,7 +335,10 @@ private bool ProcessUnexpectedArg(string argTypeName, string? argValue = null)
 
                 case UnrecognizedArgumentHandling.CollectAndContinue:
                     var arg = _enumerator.Current;
-                    _currentCommand._remainingArguments.Add(arg.Raw);
+                    if (arg != null)
+                    {
+                        _currentCommand._remainingArguments.Add(arg.Raw);
+                    }
                     return true;
 
                 case UnrecognizedArgumentHandling.StopParsingAndCollect:

src/CommandLineUtils/Internal/ReflectionHelper.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using System.Threading;
@@ -78,10 +79,10 @@ public static MemberInfo[] GetMembers(Type type)
             return GetAllMembers(type).ToArray();
         }
 
-        public static object[] BindParameters(MethodInfo method, CommandLineApplication command, CancellationToken cancellationToken)
+        public static object?[] BindParameters(MethodInfo method, CommandLineApplication command, CancellationToken cancellationToken)
         {
             var methodParams = method.GetParameters();
-            var arguments = new object[methodParams.Length];
+            var arguments = new object?[methodParams.Length];
 
             for (var i = 0; i < methodParams.Length; i++)
             {
@@ -117,15 +118,15 @@ public static object[] BindParameters(MethodInfo method, CommandLineApplication
             return arguments;
         }
 
-        public static bool IsNullableType(Type type, out Type? wrappedType)
+        public static bool IsNullableType(Type type, [NotNullWhen(true)] out Type? wrappedType)
         {
             var result = type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
             wrappedType = result ? type.GetGenericArguments().First() : null;
 
             return result;
         }
 
-        public static bool IsSpecialValueTupleType(Type type, out Type? wrappedType)
+        public static bool IsSpecialValueTupleType(Type type, [NotNullWhen(true)] out Type? wrappedType)
         {
             var result = type.IsGenericType &&
                          type.GetGenericTypeDefinition() == typeof(ValueTuple<,>) &&
@@ -135,7 +136,7 @@ public static bool IsSpecialValueTupleType(Type type, out Type? wrappedType)
             return result;
         }
 
-        public static bool IsSpecialTupleType(Type type, out Type? wrappedType)
+        public static bool IsSpecialTupleType(Type type, [NotNullWhen(true)] out Type? wrappedType)
         {
             var result = type.IsGenericType &&
                          type.GetGenericTypeDefinition() == typeof(Tuple<,>) &&

src/CommandLineUtils/Internal/ValueParsers/TypeDescriptorValueParserFactory.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 
 namespace McMaster.Extensions.CommandLineUtils.Abstractions
@@ -13,7 +14,7 @@ namespace McMaster.Extensions.CommandLineUtils.Abstractions
     /// </summary>
     internal class TypeDescriptorValueParserFactory
     {
-        public bool TryGetParser<T>(out IValueParser parser)
+        public bool TryGetParser<T>([NotNullWhen(true)] out IValueParser? parser)
         {
             var targetType = typeof(T);
             var converter = TypeDescriptor.GetConverter(targetType);
@@ -39,7 +40,7 @@ public TypeConverterValueParser(Type targetType, TypeConverter typeConverter)
 
             private TypeConverter TypeConverter { get; }
 
-            public T Parse(string argName, string value, CultureInfo culture)
+            public T Parse(string? argName, string? value, CultureInfo culture)
             {
                 try
                 {
@@ -52,7 +53,7 @@ public T Parse(string argName, string value, CultureInfo culture)
                 }
             }
 
-            object IValueParser.Parse(string argName, string value, CultureInfo culture)
+            object? IValueParser.Parse(string? argName, string? value, CultureInfo culture)
                 => Parse(argName, value, culture);
         }
     }

src/CommandLineUtils/Properties/NullabilityHelpers.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Nate McMaster.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+// Files here are for simplify annotations of nullable code and are not functional in .NET Standard 2.0
+#if NETSTANDARD2_0 || NET45
+namespace System.Diagnostics.CodeAnalysis
+{
+    // https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.codeanalysis.notnullwhenattribute?
+    [AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+    internal sealed class NotNullWhenAttribute : Attribute
+    {
+        public NotNullWhenAttribute(bool returnValue)
+        {
+        }
+    }
+
+    // https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.codeanalysis.allownullattribute
+    [System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Parameter | System.AttributeTargets.Property, Inherited=false)]
+    internal sealed class AllowNullAttribute : Attribute { }
+}
+#endif