fix: show allowed values in help text for Nullable/ValueTuple<bool,T> option/argument (#390)

Author: scott-xu

src/CommandLineUtils/HelpText/DefaultHelpTextGenerator.cs

@@ -402,12 +402,27 @@ protected virtual string Format(CommandOption option)
 
         private string[] ExtractNamesFromEnum(Type type)
         {
-            if (type == null || !type.IsEnum)
+            if (type == null)
             {
                 return Util.EmptyArray<string>();
             }
 
-            return Enum.GetNames(type);
+            if (ReflectionHelper.IsNullableType(type, out Type wrappedType))
+            {
+                return ExtractNamesFromEnum(wrappedType);
+            }
+
+            if (ReflectionHelper.IsSpecialValueTupleType(type, out var fieldInfo))
+            {
+                return ExtractNamesFromEnum(fieldInfo.FieldType);
+            }
+
+            if (type.IsEnum)
+            {
+                return Enum.GetNames(type);
+            }
+
+            return Util.EmptyArray<string>();
         }
     }
 }

src/CommandLineUtils/Internal/ReflectionHelper.cs

@@ -105,6 +105,16 @@ public static bool IsNullableType(Type type, out Type? wrappedType)
             return result;
         }
 
+        public static bool IsSpecialValueTupleType(Type type, out FieldInfo fieldInfo)
+        {
+            var result = type.IsGenericType &&
+                         type.GetGenericTypeDefinition() == typeof(ValueTuple<,>) &&
+                         type.GenericTypeArguments[0] == typeof(bool);
+            fieldInfo = result ? type.GetFields()[1] : null;
+
+            return result;
+        }
+
         private static IEnumerable<MemberInfo> GetAllMembers(Type type)
         {
             while (type != null)

test/CommandLineUtils.Tests/DefaultHelpTextGeneratorTests.cs

@@ -112,14 +112,17 @@ public void ShowHelp()
             app.Option("--rStrOpt <E>", "restricted str option desc.", CommandOptionType.SingleValue, o => o.IsRequired().Accepts().Values("Foo", "Bar"));
             app.Option<int>("--intOpt <E>", "int option desc.", CommandOptionType.SingleValue);
             app.Option<SomeEnum>("--enumOpt <E>", "enum option desc.", CommandOptionType.SingleValue);
-            app.Option<SomeEnum>("--rEnumOpt <E>", "restricted enum option desc.", CommandOptionType.SingleValue, o => o.Accepts().Values("None", "Normal"));
+            app.Option<SomeEnum>("--enumOpt2 <E>", "restricted enum option desc.", CommandOptionType.SingleValue, o => o.Accepts().Values("None", "Normal"));
+            app.Option<(bool, SomeEnum)>("--enumOpt3 <E>", "nullable enum option desc.", CommandOptionType.SingleOrNoValue);
+            app.Option<SomeEnum?>("--enumOpt4 <E>", "nullable enum option desc.", CommandOptionType.SingleOrNoValue);
             app.Argument("SomeStringArgument", "string arg desc.");
             app.Argument("RestrictedStringArgument", "restricted string arg desc.", a => a.IsRequired().Accepts().Values("Foo", "Bar"));
             app.Argument<SomeEnum>("SomeEnumArgument", "enum arg desc.");
             app.Argument<SomeEnum>("RestrictedEnumArgument", "restricted enum arg desc.", a => a.Accepts().Values("None", "Normal"));
+            app.Argument<(bool, SomeEnum)>("SomeNullableEnumArgument", "nullable enum arg desc.");
             var helpText = GetHelpText(app);
 
-            Assert.Equal(@"Usage:  [options] <SomeStringArgument> <RestrictedStringArgument> <SomeEnumArgument> <RestrictedEnumArgument>
+            Assert.Equal(@"Usage:  [options] <SomeStringArgument> <RestrictedStringArgument> <SomeEnumArgument> <RestrictedEnumArgument> <SomeNullableEnumArgument>
 
 Arguments:
   SomeStringArgument        string arg desc.
@@ -129,6 +132,8 @@ SomeEnumArgument          enum arg desc.
                             Allowed values are: None, Normal, Extreme.
   RestrictedEnumArgument    restricted enum arg desc.
                             Allowed values are: None, Normal.
+  SomeNullableEnumArgument  nullable enum arg desc.
+                            Allowed values are: None, Normal, Extreme.
 
 Options:
   -?|-h|--help              Show help information.
@@ -138,8 +143,12 @@ RestrictedEnumArgument    restricted enum arg desc.
   --intOpt <E>              int option desc.
   --enumOpt <E>             enum option desc.
                             Allowed values are: None, Normal, Extreme.
-  --rEnumOpt <E>            restricted enum option desc.
+  --enumOpt2 <E>            restricted enum option desc.
                             Allowed values are: None, Normal.
+  --enumOpt3[:<E>]          nullable enum option desc.
+                            Allowed values are: None, Normal, Extreme.
+  --enumOpt4[:<E>]          nullable enum option desc.
+                            Allowed values are: None, Normal, Extreme.
 
 ",
             helpText,
@@ -154,7 +163,7 @@ public void ShowHelpFromAttributes()
             app.Conventions.UseDefaultConventions();
             var helpText = GetHelpText(app);
 
-            Assert.Equal(@"Usage: test [options] <SomeStringArgument> <RestrictedStringArgument> <SomeEnumArgument> <RestrictedEnumArgument>
+            Assert.Equal(@"Usage: test [options] <SomeStringArgument> <RestrictedStringArgument> <SomeEnumArgument> <RestrictedEnumArgument> <SomeNullableEnumArgument>
 
 Arguments:
   SomeStringArgument                string arg desc.
@@ -164,6 +173,8 @@ SomeEnumArgument                  enum arg desc.
                                     Allowed values are: None, Normal, Extreme.
   RestrictedEnumArgument            restricted enum arg desc.
                                     Allowed values are: None, Normal.
+  SomeNullableEnumArgument          nullable enum arg desc.
+                                    Allowed values are: None, Normal, Extreme.
 
 Options:
   -strOpt|--str-opt <STR_OPT>       str option desc.
@@ -172,8 +183,12 @@ RestrictedEnumArgument            restricted enum arg desc.
   -intOpt|--int-opt <INT_OPT>       int option desc.
   -enumOpt|--verbosity <VERBOSITY>  enum option desc.
                                     Allowed values are: None, Normal, Extreme.
-  -rEnumOpt|--verb2 <VERB2>         restricted enum option desc.
+  -enumOpt2|--verb2 <VERB2>         restricted enum option desc.
                                     Allowed values are: None, Normal.
+  -enumOpt3|--verb3[:<VERB3>]       nullable enum option desc.
+                                    Allowed values are: None, Normal, Extreme.
+  -enumOpt4|--verb4[:<VERB4>]       nullable enum option desc.
+                                    Allowed values are: None, Normal, Extreme.
   -?|-h|--help                      Show help information.
 
 ",
@@ -197,10 +212,16 @@ public class MyApp
             [Option(ShortName = "enumOpt", Description = "enum option desc.")]
             public SomeEnum Verbosity { get; set; }
 
-            [Option(ShortName = "rEnumOpt", Description = "restricted enum option desc.")]
+            [Option(ShortName = "enumOpt2", Description = "restricted enum option desc.")]
             [AllowedValues("None", "Normal")]
             public SomeEnum Verb2 { get; set; }
 
+            [Option(ShortName = "enumOpt3", Description = "nullable enum option desc.")]
+            public (bool HasValue, SomeEnum Value) Verb3 { get; set; }
+
+            [Option(CommandOptionType.SingleOrNoValue, ShortName = "enumOpt4", Description = "nullable enum option desc.")]
+            public SomeEnum? Verb4 { get; set; }
+
             [Argument(0, Description = "string arg desc.")]
             public string SomeStringArgument { get; set; }
 
@@ -215,6 +236,9 @@ public class MyApp
             [Argument(3, Description = "restricted enum arg desc.")]
             [AllowedValues("None", "Normal")]
             public SomeEnum RestrictedEnumArgument { get; set; }
+
+            [Argument(4, Description = "nullable enum arg desc.")]
+            public (bool HasValue, SomeEnum Value) SomeNullableEnumArgument { get; set; }
         }
 
         [Theory]