src/commonMain/kotlin/com/infendro/cli/command/Command.kt

@@ -23,8 +23,8 @@ sealed class Command private constructor(
         if (!name.matches(Regex.COMMAND)) throw InvalidCommandName(name)
     }
 
-    fun run(args: Array<String>) {
+    fun run(vararg args: String) {
-        when (val result = ContextParser(this, args).parse()) {
+        when (val result = ContextParser(this, arrayOf(*args)).parse()) {
             is ContextParser.Result.Success -> result.context.execute()
             is ContextParser.Result.Help -> {
                 val command = result.path.last()
@@ -144,7 +144,7 @@ sealed class Command private constructor(
                 val last = commands.last()
                 if (last is Fallback<*>) throw InvalidCommandOrder()
             }
-            if (commands.any { it.name == command.name }) throw DuplicateCommand(command.name)
+            if (commands.any { it.name == command.name }) throw DuplicateCommand(command)
         }
 
         private fun validateArgument(argument: Argument<*>) {
@@ -155,12 +155,12 @@ sealed class Command private constructor(
                     argument.required && last.optional -> throw InvalidArgumentOrder()
                 }
             }
-            if (arguments.any { it.name == argument.name }) throw DuplicateArgument(argument.name)
+            if (arguments.any { it.name == argument.name }) throw DuplicateArgument(argument)
         }
 
         private fun validateOption(option: Option<*>) {
             for (name in option.names) {
-                if (options.any { name in it.names }) throw DuplicateOption(name)
+                if (options.any { name in it.names }) throw DuplicateOption(option)
             }
         }
 

src/commonMain/kotlin/com/infendro/cli/command/help/DefaultHelpRenderer.kt

@@ -3,6 +3,7 @@ package com.infendro.cli.command.help
 import com.infendro.cli.command.Command
 import com.infendro.cli.command.argument.Argument
 import com.infendro.cli.command.option.Option
+import kotlin.reflect.KClass
 
 object DefaultHelpRenderer : HelpRenderer {
     override fun render(path: List<Command>) = buildString {
@@ -40,11 +41,7 @@ object DefaultHelpRenderer : HelpRenderer {
                 argument.min == 1 && argument.max == 1 -> append("<${argument.name}>")
                 argument.min == 0 && argument.max == 1 -> append("[<${argument.name}>]")
                 else -> {
-                    val range = when {
+                    val range = renderRange(argument.min, argument.max)
-                        argument.unbounded -> "{${argument.min},}"
-                        argument.min == argument.max -> "{${argument.min}}"
-                        else -> "{${argument.min},${argument.max}}"
-                    }
                     append("<${argument.name}>$range")
                 }
             }
@@ -64,11 +61,7 @@ object DefaultHelpRenderer : HelpRenderer {
                 option.min == 1 && option.max == 1 -> append("($text)")
                 option.min == 0 && option.max == 1 -> append("[$text]")
                 else -> {
-                    val range = when {
+                    val range = renderRange(option.min, option.max)
-                        option.unbounded -> "{${option.min},}"
-                        option.min == option.max -> "{${option.min}}"
-                        else -> "{${option.min},${option.max}}"
-                    }
                     append("($text)$range")
                 }
             }
@@ -80,7 +73,11 @@ object DefaultHelpRenderer : HelpRenderer {
         appendLine("Commands:")
         for (command in commands) {
             val name = when {
-                command is Command.Fallback<*> -> "<${command.name}>"
+                command is Command.Fallback<*> -> {
+                    val name = command.name
+                    val type = command.parser.type.name
+                    "<$name> ($type)"
+                }
                 else -> command.name
             }
             appendLine("  * $name")
@@ -90,7 +87,10 @@ object DefaultHelpRenderer : HelpRenderer {
     private fun StringBuilder.arguments(arguments: List<Argument<*>>) {
         appendLine("Arguments:")
         for (argument in arguments) {
-            appendLine("  * ${argument.name}")
+            val name = argument.name
+            val type = argument.parser.type.name
+            val range = renderRangeFull(argument.min, argument.max)
+            appendLine("  * $name ($type, $range)")
         }
     }
 
@@ -98,7 +98,9 @@ object DefaultHelpRenderer : HelpRenderer {
         appendLine("Options:")
         for (option in options) {
             val name = option.names.joinToString(" | ") { it.withPrefix() }
-            appendLine("  * $name")
+            val type = option.parser.type.name
+            val range = renderRangeFull(option.min, option.max)
+            appendLine("  * $name ($type, $range)")
         }
     }
 
@@ -106,4 +108,23 @@ object DefaultHelpRenderer : HelpRenderer {
         length == 1 -> "-$this"
         else -> "--$this"
     }
+
+    private val KClass<*>.name: String
+        get() = simpleName ?: "Unknown"
+
+    private fun renderRange(min: Int, max: Int?) = when {
+        max == null -> "{$min,}"
+        min == max -> "{$min}"
+        else -> "{$min,$max}"
+    }
+
+    private fun renderRangeFull(min: Int, max: Int?) = when {
+        min == 1 && max == 1 -> "required"
+        min == 0 && max == 1 -> "optional"
+        else -> when {
+            max == null -> "at least $min"
+            min == max -> "exactly $min"
+            else -> "between $min and $max"
+        }
+    }
 }