Improve preview directive

CliFx/CliApplication.cs

@@ -47,35 +47,51 @@ namespace CliFx
             return null;
         }
 
-        private int? HandlePreviewDirective(CommandLineInput commandLineInput)
+        private int? HandlePreviewDirective(ApplicationSchema applicationSchema, CommandLineInput commandLineInput)
         {
             var isPreviewMode = _configuration.IsPreviewModeAllowed && commandLineInput.IsPreviewDirectiveSpecified;
             if (!isPreviewMode)
                 return null;
 
-            // Render command name
-            _console.Output.WriteLine($"Arguments: {string.Join(" ", commandLineInput.Arguments)}");
-            _console.Output.WriteLine();
+            var commandSchema = applicationSchema.TryFindCommand(commandLineInput, out var argumentOffset);
 
-            // Render directives
-            _console.Output.WriteLine("Directives:");
-            foreach (var directive in commandLineInput.Directives)
+            _console.Output.WriteLine("Parser preview:");
+
+            // Command name
+            if (commandSchema != null && argumentOffset > 0)
             {
-                _console.Output.Write(" ");
-                _console.Output.WriteLine(directive);
+                _console.WithForegroundColor(ConsoleColor.Cyan, () =>
+                    _console.Output.Write(commandSchema.Name));
+
+                _console.Output.Write(' ');
             }
 
-            // Margin
-            _console.Output.WriteLine();
+            // Parameters
+            foreach (var parameter in commandLineInput.Arguments.Skip(argumentOffset))
+            {
+                _console.Output.Write('<');
 
-            // Render options
-            _console.Output.WriteLine("Options:");
+                _console.WithForegroundColor(ConsoleColor.White, () =>
+                    _console.Output.Write(parameter));
+
+                _console.Output.Write('>');
+                _console.Output.Write(' ');
+            }
+
+            // Options
             foreach (var option in commandLineInput.Options)
             {
-                _console.Output.Write(" ");
-                _console.Output.WriteLine(option);
+                _console.Output.Write('[');
+
+                _console.WithForegroundColor(ConsoleColor.White, () =>
+                    _console.Output.Write(option));
+
+                _console.Output.Write(']');
+                _console.Output.Write(' ');
             }
 
+            _console.Output.WriteLine();
+
             return 0;
         }
 
@@ -91,9 +107,7 @@ namespace CliFx
             return 0;
         }
 
-        private int? HandleHelpOption(
-            ApplicationSchema applicationSchema,
-            CommandLineInput commandLineInput)
+        private int? HandleHelpOption(ApplicationSchema applicationSchema, CommandLineInput commandLineInput)
         {
             // Help is rendered either when it's requested or when the user provides no arguments and there is no default command
             var shouldRenderHelp =
@@ -139,7 +153,7 @@ namespace CliFx
 
                 return
                     await HandleDebugDirectiveAsync(commandLineInput) ??
-                    HandlePreviewDirective(commandLineInput) ??
+                    HandlePreviewDirective(applicationSchema, commandLineInput) ??
                     HandleVersionOption(commandLineInput) ??
                     HandleHelpOption(applicationSchema, commandLineInput) ??
                     await HandleCommandExecutionAsync(applicationSchema, commandLineInput, environmentVariables);

CliFx/Domain/ApplicationSchema.cs

@@ -43,7 +43,8 @@ namespace CliFx.Domain
                 ? Commands.Where(c => TryFindParentCommand(c.Name)?.MatchesName(parentCommandName) == true).ToArray()
                 : Commands.Where(c => !string.IsNullOrWhiteSpace(c.Name) && TryFindParentCommand(c.Name) == null).ToArray();
 
-        private CommandSchema? TryFindCommand(CommandLineInput commandLineInput, out int argumentOffset)
+        // TODO: this out parameter is not a really nice design
+        public CommandSchema? TryFindCommand(CommandLineInput commandLineInput, out int argumentOffset)
         {
             // Try to find the command that contains the most of the input arguments in its name
             for (var i = commandLineInput.Arguments.Count; i >= 0; i--)

CliFx/Domain/CommandArgumentSchema.cs

@@ -65,7 +65,7 @@ namespace CliFx.Domain
         private static readonly IFormatProvider ConversionFormatProvider = CultureInfo.InvariantCulture;
 
         private static readonly IReadOnlyDictionary<Type, Func<string, object>> PrimitiveConverters =
-            new Dictionary<Type, Func<string, object>>
+            new Dictionary<Type, Func<string?, object>>
             {
                 [typeof(object)] = v => v,
                 [typeof(string)] = v => v,

CliFx/Domain/CommandOptionSchema.cs

@@ -36,7 +36,7 @@ namespace CliFx.Domain
             IsRequired = isRequired;
         }
 
-        public bool MatchesName(string name) =>
+        public bool MatchesName(string? name) =>
             !string.IsNullOrWhiteSpace(Name) &&
             string.Equals(Name, name, StringComparison.OrdinalIgnoreCase);
 

CliFx/Domain/CommandSchema.cs

@@ -38,7 +38,7 @@ namespace CliFx.Domain
             Parameters = parameters;
         }
 
-        public bool MatchesName(string name) => string.Equals(name, Name, StringComparison.OrdinalIgnoreCase);
+        public bool MatchesName(string? name) => string.Equals(name, Name, StringComparison.OrdinalIgnoreCase);
 
         private void InjectParameters(ICommand command, IReadOnlyList<string> parameterInputs)
         {