Automatically display default values of options in the help page (#1032)

Fixes #973

src/Spectre.Console.Cli/ConfiguratorExtensions.cs

@@ -40,6 +40,23 @@ public static class ConfiguratorExtensions
         return configurator;
     }
 
+    /// <summary>
+    /// Hides the <c>DEFAULT</c> column that lists default values coming from the
+    /// <see cref="DefaultValueAttribute"/> in the options help text.
+    /// </summary>
+    /// <param name="configurator">The configurator.</param>
+    /// <returns>A configurator that can be used to configure the application further.</returns>
+    public static IConfigurator HideOptionDefaultValues(this IConfigurator configurator)
+    {
+        if (configurator == null)
+        {
+            throw new ArgumentNullException(nameof(configurator));
+        }
+
+        configurator.Settings.ShowOptionDefaultValues = false;
+        return configurator;
+    }
+
     /// <summary>
     /// Configures the console.
     /// </summary>

src/Spectre.Console.Cli/ICommandAppSettings.cs

@@ -15,6 +15,11 @@ public interface ICommandAppSettings
     /// </summary>
     string? ApplicationVersion { get; set; }
 
+    /// <summary>
+    /// Gets or sets a value indicating whether any default values for command options are shown in the help text.
+    /// </summary>
+    bool ShowOptionDefaultValues { get; set; }
+
     /// <summary>
     /// Gets or sets the <see cref="IAnsiConsole"/>.
     /// </summary>

src/Spectre.Console.Cli/Internal/CommandExecutor.cs

@@ -53,7 +53,7 @@ internal sealed class CommandExecutor
         if (parsedResult.Tree == null)
         {
             // Display help.
-            configuration.Settings.Console.SafeRender(HelpWriter.Write(model));
+            configuration.Settings.Console.SafeRender(HelpWriter.Write(model, configuration.Settings.ShowOptionDefaultValues));
             return 0;
         }
 
@@ -62,7 +62,7 @@ internal sealed class CommandExecutor
         if (leaf.Command.IsBranch || leaf.ShowHelp)
         {
             // Branches can't be executed. Show help.
-            configuration.Settings.Console.SafeRender(HelpWriter.WriteCommand(model, leaf.Command));
+            configuration.Settings.Console.SafeRender(HelpWriter.WriteCommand(model, leaf.Command, configuration.Settings.ShowOptionDefaultValues));
             return leaf.ShowHelp ? 0 : 1;
         }
 
@@ -70,7 +70,7 @@ internal sealed class CommandExecutor
         if (leaf.Command.IsDefaultCommand && args.Count() == 0 && leaf.Command.Parameters.Any(p => p.Required))
         {
             // Display help for default command.
-            configuration.Settings.Console.SafeRender(HelpWriter.WriteCommand(model, leaf.Command));
+            configuration.Settings.Console.SafeRender(HelpWriter.WriteCommand(model, leaf.Command, configuration.Settings.ShowOptionDefaultValues));
             return 1;
         }
 

src/Spectre.Console.Cli/Internal/Configuration/CommandAppSettings.cs

@@ -4,6 +4,7 @@ internal sealed class CommandAppSettings : ICommandAppSettings
 {
     public string? ApplicationName { get; set; }
     public string? ApplicationVersion { get; set; }
+    public bool ShowOptionDefaultValues { get; set; }
     public IAnsiConsole? Console { get; set; }
     public ICommandInterceptor? Interceptor { get; set; }
     public ITypeRegistrarFrontend Registrar { get; set; }
@@ -22,6 +23,7 @@ internal sealed class CommandAppSettings : ICommandAppSettings
     {
         Registrar = new TypeRegistrar(registrar);
         CaseSensitivity = CaseSensitivity.All;
+        ShowOptionDefaultValues = true;
     }
 
     public bool IsTrue(Func<CommandAppSettings, bool> func, string environmentVariableName)

src/Spectre.Console.Cli/Internal/HelpWriter.cs

@@ -34,42 +34,45 @@ internal static class HelpWriter
         public string? Value { get; }
         public bool? ValueIsOptional { get; }
         public string? Description { get; }
+        public object? DefaultValue { get; }
 
-        public HelpOption(string? @short, string? @long, string? @value, bool? valueIsOptional, string? description)
+        public HelpOption(string? @short, string? @long, string? @value, bool? valueIsOptional, string? description, object? defaultValue)
         {
             Short = @short;
             Long = @long;
             Value = value;
             ValueIsOptional = valueIsOptional;
             Description = description;
+            DefaultValue = defaultValue;
         }
 
         public static IReadOnlyList<HelpOption> Get(CommandModel model, CommandInfo? command)
         {
             var parameters = new List<HelpOption>();
-            parameters.Add(new HelpOption("h", "help", null, null, "Prints help information"));
+            parameters.Add(new HelpOption("h", "help", null, null, "Prints help information", null));
 
             // At the root and no default command?
             if (command == null && model?.DefaultCommand == null)
             {
-                parameters.Add(new HelpOption("v", "version", null, null, "Prints version information"));
+                parameters.Add(new HelpOption("v", "version", null, null, "Prints version information", null));
             }
 
             parameters.AddRange(command?.Parameters.OfType<CommandOption>().Where(o => !o.IsHidden).Select(o =>
                 new HelpOption(
                     o.ShortNames.FirstOrDefault(), o.LongNames.FirstOrDefault(),
-                    o.ValueName, o.ValueIsOptional, o.Description))
+                    o.ValueName, o.ValueIsOptional, o.Description,
+                    o.ParameterKind == ParameterKind.Flag && o.DefaultValue?.Value is false ? null : o.DefaultValue?.Value))
                 ?? Array.Empty<HelpOption>());
             return parameters;
         }
     }
 
-    public static IEnumerable<IRenderable> Write(CommandModel model)
+    public static IEnumerable<IRenderable> Write(CommandModel model, bool writeOptionsDefaultValues)
     {
-        return WriteCommand(model, null);
+        return WriteCommand(model, null, writeOptionsDefaultValues);
     }
 
-    public static IEnumerable<IRenderable> WriteCommand(CommandModel model, CommandInfo? command)
+    public static IEnumerable<IRenderable> WriteCommand(CommandModel model, CommandInfo? command, bool writeOptionsDefaultValues)
     {
         var container = command as ICommandContainer ?? model;
         var isDefaultCommand = command?.IsDefaultCommand ?? false;
@@ -79,7 +82,7 @@ internal static class HelpWriter
         result.AddRange(GetUsage(model, command));
         result.AddRange(GetExamples(model, command));
         result.AddRange(GetArguments(command));
-        result.AddRange(GetOptions(model, command));
+        result.AddRange(GetOptions(model, command, writeOptionsDefaultValues));
         result.AddRange(GetCommands(model, container, isDefaultCommand));
 
         return result;
@@ -266,7 +269,7 @@ internal static class HelpWriter
         return result;
     }
 
-    private static IEnumerable<IRenderable> GetOptions(CommandModel model, CommandInfo? command)
+    private static IEnumerable<IRenderable> GetOptions(CommandModel model, CommandInfo? command, bool writeDefaultValues)
     {
         // Collect all options into a single structure.
         var parameters = HelpOption.Get(model, command);
@@ -282,8 +285,16 @@ internal static class HelpWriter
                 new Markup(Environment.NewLine),
             };
 
+        var helpOptions = parameters.ToArray();
+        var defaultValueColumn = writeDefaultValues && helpOptions.Any(e => e.DefaultValue != null);
+
         var grid = new Grid();
         grid.AddColumn(new GridColumn { Padding = new Padding(4, 4), NoWrap = true });
+        if (defaultValueColumn)
+        {
+            grid.AddColumn(new GridColumn { Padding = new Padding(0, 0, 4, 0) });
+        }
+
         grid.AddColumn(new GridColumn { Padding = new Padding(0, 0) });
 
         static string GetOptionParts(HelpOption option)
@@ -327,11 +338,22 @@ internal static class HelpWriter
             return builder.ToString();
         }
 
-        foreach (var option in parameters.ToArray())
+        if (defaultValueColumn)
         {
-            grid.AddRow(
+            grid.AddRow(" ", "[lime]DEFAULT[/]", " ");
-                GetOptionParts(option),
+        }
-                option.Description?.TrimEnd('.') ?? " ");
+
+        foreach (var option in helpOptions)
+        {
+            var columns = new List<string> { GetOptionParts(option) };
+            if (defaultValueColumn)
+            {
+                columns.Add(option.DefaultValue == null ? " " : $"[bold]{option.DefaultValue.ToString().EscapeMarkup()}[/]");
+            }
+
+            columns.Add(option.Description?.TrimEnd('.') ?? " ");
+
+            grid.AddRow(columns.ToArray());
         }
 
         result.Add(grid);

test/Spectre.Console.Cli.Tests/Expectations/Help/Command.Output.verified.txt

@@ -8,10 +8,11 @@ ARGUMENTS:
     [LEGS]    The number of legs
 
 OPTIONS:
+                             DEFAULT
     -h, --help                          Prints help information
     -a, --alive                         Indicates whether or not the animal is alive
     -n, --name <VALUE>
-        --agility <VALUE>    The agility between 0 and 100
+        --agility <VALUE>    10         The agility between 0 and 100
 
 COMMANDS:
     lion <TEETH>    The lion command

test/Spectre.Console.Cli.Tests/Expectations/Help/Command_Hide_Default.Output.verified.txt

@@ -0,0 +1,17 @@
+DESCRIPTION:
+Contains settings for a cat.
+
+USAGE:
+    myapp cat [LEGS] [OPTIONS] <COMMAND>
+
+ARGUMENTS:
+    [LEGS]    The number of legs
+
+OPTIONS:
+    -h, --help               Prints help information
+    -a, --alive              Indicates whether or not the animal is alive
+    -n, --name <VALUE>
+        --agility <VALUE>    The agility between 0 and 100
+
+COMMANDS:
+    lion <TEETH>    The lion command

test/Spectre.Console.Cli.Tests/Expectations/Help/Default.Output.verified.txt

@@ -9,8 +9,9 @@ ARGUMENTS:
     [LEGS]     The number of legs
 
 OPTIONS:
+                             DEFAULT
     -h, --help                          Prints help information
     -a, --alive                         Indicates whether or not the animal is alive
     -n, --name <VALUE>
-        --agility <VALUE>    The agility between 0 and 100
+        --agility <VALUE>    10         The agility between 0 and 100
     -c <CHILDREN>                       The number of children the lion has

test/Spectre.Console.Cli.Tests/Expectations/Help/DefaultExamples.Output.verified.txt

@@ -12,8 +12,9 @@ ARGUMENTS:
     [LEGS]     The number of legs
 
 OPTIONS:
+                             DEFAULT
     -h, --help                          Prints help information
     -a, --alive                         Indicates whether or not the animal is alive
     -n, --name <VALUE>
-        --agility <VALUE>    The agility between 0 and 100
+        --agility <VALUE>    10         The agility between 0 and 100
     -c <CHILDREN>                       The number of children the lion has

test/Spectre.Console.Cli.Tests/Expectations/Help/Default_Without_Args.Output.verified.txt

@@ -9,8 +9,9 @@ ARGUMENTS:
     [LEGS]     The number of legs
 
 OPTIONS:
+                             DEFAULT
     -h, --help                          Prints help information
     -a, --alive                         Indicates whether or not the animal is alive
     -n, --name <VALUE>
-        --agility <VALUE>    The agility between 0 and 100
+        --agility <VALUE>    10         The agility between 0 and 100
     -c <CHILDREN>                       The number of children the lion has

test/Spectre.Console.Cli.Tests/Expectations/Help/Default_Without_Args_Additional.Output.verified.txt

@@ -1,4 +1,4 @@
-DESCRIPTION:
+DESCRIPTION:
 The lion command.
 
 USAGE:
@@ -9,10 +9,11 @@ ARGUMENTS:
     [LEGS]     The number of legs
 
 OPTIONS:
+                             DEFAULT
     -h, --help                          Prints help information
     -a, --alive                         Indicates whether or not the animal is alive
     -n, --name <VALUE>
-        --agility <VALUE>    The agility between 0 and 100
+        --agility <VALUE>    10         The agility between 0 and 100
     -c <CHILDREN>                       The number of children the lion has
 
 COMMANDS:

test/Spectre.Console.Cli.Tests/Unit/CommandAppTests.Help.cs

@@ -99,6 +99,30 @@ public sealed partial class CommandAppTests
             return Verifier.Verify(result.Output);
         }
 
+        [Fact]
+        [Expectation("Command_Hide_Default")]
+        public Task Should_Not_Print_Default_Column()
+        {
+            // Given
+            var fixture = new CommandAppTester();
+            fixture.Configure(configurator =>
+            {
+                configurator.SetApplicationName("myapp");
+                configurator.AddBranch<CatSettings>("cat", animal =>
+                {
+                    animal.SetDescription("Contains settings for a cat.");
+                    animal.AddCommand<LionCommand>("lion");
+                });
+                configurator.HideOptionDefaultValues();
+            });
+
+            // When
+            var result = fixture.Run("cat", "--help");
+
+            // Then
+            return Verifier.Verify(result.Output);
+        }
+
         [Fact]
         [Expectation("Leaf")]
         public Task Should_Output_Leaf_Correctly()