Fix empty description help section

Author: marko1olo

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

@@ -466,7 +466,6 @@ public void Help_default_sections_can_be_wrapped()
             command.Parse("test -h").Invoke(new() { Output = output });
 
             output.ToString().Should().Be(
-                $"Description:{NewLine}{NewLine}" +
                 $"Usage:{NewLine}  test [options]{NewLine}{NewLine}" +
                 $"Options:{NewLine}" +
                 $"  --option   option {NewLine}" +
@@ -534,4 +533,4 @@ private string GetDefaultHelp(Command command, bool trimOneNewline = true)
             return output;
         }
     }
-}
+}

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

@@ -74,6 +74,20 @@ public void Synopsis_section_properly_wraps_description()
             _console.ToString().Should().Contain(expected);
         }
 
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData(" ")]
+        public void Synopsis_section_is_not_rendered_when_description_is_empty(string? description)
+        {
+            var command = new RootCommand(description);
+
+            _helpBuilder.Write(command, _console);
+
+            _console.ToString().Should().NotContain("Description:");
+            _console.ToString().Should().Contain("Usage:");
+        }
+
         [Fact]
         public void Command_name_in_synopsis_can_be_specified()
         {

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

@@ -185,6 +185,11 @@ public static IEnumerable<Func<HelpContext, bool>> GetLayout()
         public static Func<HelpContext, bool> SynopsisSection() =>
             ctx =>
             {
+                if (string.IsNullOrWhiteSpace(ctx.Command.Description))
+                {
+                    return false;
+                }
+
                 ctx.HelpBuilder.WriteHeading(LocalizationResources.HelpDescriptionTitle(), ctx.Command.Description, ctx.Output);
                 return true;
             };