Show [default: true] in help for bool options/arguments with explicit default factories

src/System.CommandLine.Tests/Help/HelpBuilderTests.cs

@@ -1350,6 +1350,27 @@ public void Help_describes_default_value_for_option_with_argument_having_default
             help.Should().Contain($"[default: the-arg-value]");
         }
 
+        [Fact]
+        public void Help_describes_default_value_for_boolean_option_when_default_value_is_true()
+        {
+            var command = new Command("the-command", "command help")
+            {
+                new Option<bool>("--bool-default")
+                {
+                    Description = "Bool value with default",
+                    DefaultValueFactory = _ => true
+                }
+            };
+
+            HelpBuilder helpBuilder = GetHelpBuilder(SmallMaxWidth);
+
+            helpBuilder.Write(command, _console);
+
+            var help = _console.ToString();
+
+            help.Should().Contain("--bool-default").And.Contain("[default: true]");
+        }
+
         [Fact]
         public void Option_arguments_with_default_values_that_are_enumerable_display_pipe_delimited_list()
         {

src/System.CommandLine/Help/HelpBuilder.Default.cs

@@ -24,16 +24,18 @@ public static string GetArgumentDefaultValue(Symbol symbol)
             return symbol switch
             {
                 Argument argument => ShouldShowDefaultValue(argument) 
-                                         ? ToString(argument.GetDefaultValue()) 
+                                         ? ToString(argument.GetDefaultValue(), argument.ValueType) 
                                          : "",
                 Option option => ShouldShowDefaultValue(option) 
-                                     ? ToString(option.GetDefaultValue()) 
+                                     ? ToString(option.GetDefaultValue(), option.ValueType) 
                                      : "",
                 _ => throw new InvalidOperationException("Symbol must be an Argument or Option.")
             };
 
-            static string ToString(object? value) => value switch
+            static string ToString(object? value, Type valueType) => value switch
             {
+                _ when (valueType == typeof(bool) || valueType == typeof(bool?)) && value is not true => string.Empty,
+                bool boolValue => boolValue ? "true" : "false",
                 null => string.Empty,
                 string str => str,
                 IEnumerable enumerable => string.Join("|", enumerable.Cast<object>()),
@@ -50,12 +52,10 @@ public static bool ShouldShowDefaultValue(Symbol symbol) =>
             };
 
         public static bool ShouldShowDefaultValue(Option option) =>
-            option.HasDefaultValue && 
-            !(option.ValueType == typeof(bool) || option.ValueType == typeof(bool?));
+            option.HasDefaultValue;
 
         public static bool ShouldShowDefaultValue(Argument argument) =>
-            argument.HasDefaultValue && 
-            !(argument.ValueType == typeof(bool) || argument.ValueType == typeof(bool?));
+            argument.HasDefaultValue;
 
         /// <summary>
         /// Gets the description for an argument (typically used in the second column text in the arguments section).
@@ -289,4 +289,4 @@ public static Func<HelpContext, bool> OptionsSection() =>
         public static Func<HelpContext, bool> AdditionalArgumentsSection() =>
             ctx => ctx.HelpBuilder.WriteAdditionalArguments(ctx);
     }
-}
+}

src/System.CommandLine/Help/HelpBuilder.cs

@@ -475,10 +475,9 @@ string GetOptionOrCommandDefaultValue()
                 }
 
                 var isSingleArgument = defaultArguments.Length == 1;
-                var argumentDefaultValues = string.Join(
-                    ", ",
-                    defaultArguments
-                        .Select(argument => GetArgumentDefaultValue(symbol, argument, isSingleArgument, context)));
+                var argumentDefaultValues = string.Join(", ", defaultArguments
+                    .Select(argument => GetArgumentDefaultValue(symbol, argument, isSingleArgument, context))
+                    .Where(defaultValue => !string.IsNullOrEmpty(defaultValue)));
 
                 return string.IsNullOrEmpty(argumentDefaultValues)
                            ? ""