feat: Show arguments description in help output

Closes #33

Author: kylef

CHANGELOG.md

@@ -8,11 +8,14 @@
 - Adds support for variadic options, allowing the user to repeat options to
   provide additional values.
   [#37](https://github.com/kylef/Commander/issues/37)
+- Argument descriptions are now printed in command help.
+  [#33](https://github.com/kylef/Commander/issues/33)
 
 ### Bug Fixes
 
 - `VaradicArgument` has been renamed to `VariadicArgument`.
 
+
 ## 0.5.0
 
 ### Enhancements

Sources/ArgumentDescription.swift

@@ -324,6 +324,19 @@ class Help : Error, ANSIConvertible, CustomStringConvertible {
           output.append("    + \(command.name)")
         }
       }
+      output.append("")
+    } else if !arguments.isEmpty {
+      output.append("Arguments:")
+      output.append("")
+
+      output += arguments.map { argument in
+        if let description = argument.description {
+          return "    \(argument.name) - \(description)"
+        } else {
+          return "    \(argument.name)"
+        }
+      }
+
       output.append("")
     }
 
@@ -369,6 +382,19 @@ class Help : Error, ANSIConvertible, CustomStringConvertible {
           output.append("    + \(ANSI.green)\(command.name)\(ANSI.reset)")
         }
       }
+      output.append("")
+    } else if !arguments.isEmpty {
+      output.append("Arguments:")
+      output.append("")
+
+      output += arguments.map { argument in
+        if let description = argument.description {
+          return "    \(ANSI.blue)\(argument.name)\(ANSI.reset) - \(description)"
+        } else {
+          return "    \(ANSI.blue)\(argument.name)\(ANSI.reset)"
+        }
+      }
+
       output.append("")
     }
 

Tests/CommanderTests/ArgumentDescriptionSpec.swift

@@ -0,0 +1,17 @@
+import Spectre
+@testable import Commander
+
+
+public func testArgumentDescription() {
+  describe("help") {
+    $0.it("shows arguments") {
+      let help = Help([
+        BoxedArgumentDescriptor(value: Argument<String>("arg1")),
+        BoxedArgumentDescriptor(value: Argument<String>("arg2", description: "an example")),
+      ])
+
+      try expect(help.description) == "Arguments:\n\n    arg1\n    arg2 - an example\n"
+      try expect(help.ansiDescription) == "Arguments:\n\n    \(ANSI.blue)arg1\(ANSI.reset)\n    \(ANSI.blue)arg2\(ANSI.reset) - an example\n"
+    }
+  }
+}

Tests/CommanderTests/XCTest.swift

@@ -5,6 +5,7 @@ class CommanderTests: XCTestCase {
   func testRunCommander() {
     testArgumentParser()
     testArgumentConvertible()
+    testArgumentDescription()
     testCommandType()
     testCommand()
     testGroup()

Tests/LinuxMain.swift

@@ -2,6 +2,7 @@ import CommanderTests
 
 testArgumentParser()
 testArgumentConvertible()
+testArgumentDescription()
 testCommandType()
 testCommand()
 testGroup()