refactor: enable nullable ref type checking (#425)

Author: natemcmaster

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;