Fix #862. Properties with required modifier should be required.

src/CommandLine/CommandLine.csproj

@@ -3,7 +3,7 @@
 	<PropertyGroup>
 		<AssemblyName>CommandLine</AssemblyName>
 		<OutputType>Library</OutputType>
-		<TargetFrameworks>netstandard2.0;net40;net45;net461</TargetFrameworks>
+		<TargetFrameworks>netstandard2.0;net40;net45;net461;net7</TargetFrameworks>
 		<DefineConstants>$(DefineConstants);CSX_EITHER_INTERNAL;CSX_REM_EITHER_BEYOND_2;CSX_ENUM_INTERNAL;ERRH_INTERNAL;CSX_MAYBE_INTERNAL;CSX_REM_EITHER_FUNC;CSX_REM_CRYPTORAND;ERRH_ADD_MAYBE_METHODS</DefineConstants>
 		<DefineConstants Condition="'$(BuildTarget)' != 'fsharp'">$(DefineConstants);SKIP_FSHARP</DefineConstants>
 		<GenerateDocumentationFile>true</GenerateDocumentationFile>

src/CommandLine/Core/Specification.cs

@@ -4,6 +4,8 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using CommandLine.Infrastructure;
 using CSharpx;
 
@@ -54,7 +56,7 @@ protected Specification(SpecificationType tag, bool required, Maybe<int> min, Ma
             this.hidden = hidden;
         }
 
-        public SpecificationType Tag 
+        public SpecificationType Tag
         {
             get { return tag; }
         }
@@ -110,28 +112,40 @@ public bool Hidden
         }
 
         public static Specification FromProperty(PropertyInfo property)
-        {       
+        {
             var attrs = property.GetCustomAttributes(true);
+
+#if NET7_0_OR_GREATER
+            var isRequired = attrs.OfType<RequiredMemberAttribute>().Any();
+#else
+            var isRequired = false;
+#endif
+
             var oa = attrs.OfType<OptionAttribute>();
             if (oa.Count() == 1)
             {
-                var spec = OptionSpecification.FromAttribute(oa.Single(), property.PropertyType,
-                    ReflectionHelper.GetNamesOfEnum(property.PropertyType)); 
+                var optionAttribute = oa.Single();
+                optionAttribute.Required |= isRequired;
+                var spec = OptionSpecification.FromAttribute(optionAttribute, property.PropertyType,
+                                                             ReflectionHelper.GetNamesOfEnum(property.PropertyType));
 
                 if (spec.ShortName.Length == 0 && spec.LongName.Length == 0)
                 {
                     return spec.WithLongName(property.Name.ToLowerInvariant());
                 }
+
                 return spec;
             }
 
             var va = attrs.OfType<ValueAttribute>();
             if (va.Count() == 1)
             {
-                return ValueSpecification.FromAttribute(va.Single(), property.PropertyType,
-                    property.PropertyType.GetTypeInfo().IsEnum
-                        ? Enum.GetNames(property.PropertyType)
-                        : Enumerable.Empty<string>());
+                var valueAttribute = va.Single();
+                valueAttribute.Required |= isRequired;
+                return ValueSpecification.FromAttribute(valueAttribute, property.PropertyType,
+                                                        property.PropertyType.GetTypeInfo().IsEnum
+                                                            ? Enum.GetNames(property.PropertyType)
+                                                            : Enumerable.Empty<string>());
             }
 
             throw new InvalidOperationException();

src/CommandLine/Core/TokenPartitioner.cs

@@ -15,8 +15,6 @@ Tuple<IEnumerable<KeyValuePair<string, IEnumerable<string>>>, IEnumerable<string
                 IEnumerable<Token> tokens,
                 Func<string, Maybe<TypeDescriptor>> typeLookup)
         {
-            IEqualityComparer<Token> tokenComparer = ReferenceEqualityComparer.Default;
-
             var tokenList = tokens.Memoize();
             var partitioned = PartitionTokensByType(tokenList, typeLookup);
             var switches = partitioned.Item1;

tests/CommandLine.Tests/CommandLine.Tests.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>net461;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net461;net7;netcoreapp3.1</TargetFrameworks>
     <DefineConstants Condition="'$(BuildTarget)' != 'fsharp'">$(DefineConstants);SKIP_FSHARP</DefineConstants>
     <AssemblyOriginatorKeyFile>..\..\CommandLine.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>

tests/CommandLine.Tests/Unit/Issue862Tests.cs

@@ -0,0 +1,29 @@
+using System;
+using FluentAssertions;
+using Xunit;
+
+namespace CommandLine.Tests.Unit
+{
+    #if NET7_0_OR_GREATER
+    public class Issue862Tests
+    {
+
+        [Fact]
+        public void Properties_with_required_modifier_are_required()
+        {
+            var arguments = Array.Empty<string>();
+            var result = new Parser().ParseArguments<Options>(arguments);
+
+            result.Errors.Should().ContainSingle(e => e.Tag == ErrorType.MissingRequiredOptionError);
+            result.Tag.Should().Be(ParserResultType.NotParsed);
+        }
+
+        private class Options
+        {
+            [Option("cols")]
+            public required int Cols { get; set; }
+        }
+    }
+
+    #endif
+}