Added async versions of WithParsed extension methods

Author: joseangelmt

src/CommandLine/ParserResultExtensionsAsync.cs

@@ -0,0 +1,63 @@
+// Copyright 2005-2015 Giacomo Stelluti Scala & Contributors. All rights reserved. See License.md in the project root for license information.
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace CommandLine
+{
+    public static partial class ParserResultExtensions
+    {
+        /// <summary>
+        /// Executes asynchronously <paramref name="action"/> if <see cref="CommandLine.ParserResult{T}"/> contains
+        /// parsed values.
+        /// </summary>
+        /// <typeparam name="T">Type of the target instance built with parsed value.</typeparam>
+        /// <param name="result">An <see cref="CommandLine.ParserResult{T}"/> instance.</param>
+        /// <param name="action">The <see cref="Func{T, Task}"/> to execute.</param>
+        /// <returns>The same <paramref name="result"/> instance as a <see cref="Task"/> instance.</returns>
+        public static async Task<ParserResult<T>> WithParsedAsync<T>(this ParserResult<T> result, Func<T, Task> action)
+        {
+            if (result is Parsed<T> parsed)
+            {
+                await action(parsed.Value);
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Executes asynchronously <paramref name="action"/> if parsed values are of <typeparamref name="T"/>.
+        /// </summary>
+        /// <typeparam name="T">Type of the target instance built with parsed value.</typeparam>
+        /// <param name="result">An verb result instance.</param>
+        /// <param name="action">The <see cref="Func{T, Task}"/> to execute.</param>
+        /// <returns>The same <paramref name="result"/> instance as a <see cref="Task"/> instance.</returns>
+        public static async Task<ParserResult<object>> WithParsedAsync<T>(this ParserResult<object> result, Func<T, Task> action)
+        {
+            if (result is Parsed<object> parsed)
+            {
+                if (parsed.Value is T value)
+                {
+                    await action(value);
+                }
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Executes asynchronously <paramref name="action"/> if <see cref="CommandLine.ParserResult{T}"/> lacks
+        /// parsed values and contains errors.
+        /// </summary>
+        /// <typeparam name="T">Type of the target instance built with parsed value.</typeparam>
+        /// <param name="result">An <see cref="CommandLine.ParserResult{T}"/> instance.</param>
+        /// <param name="action">The <see cref="System.Func{Task}"/> delegate to execute.</param>
+        /// <returns>The same <paramref name="result"/> instance as a <see cref="Task"/> instance.</returns>
+        public static async Task<ParserResult<T>> WithNotParsedAsync<T>(this ParserResult<T> result, Func<IEnumerable<Error>, Task> action)
+        {
+            if (result is NotParsed<T> notParsed)
+            {
+                await action(notParsed.Errors);
+            }
+            return result;
+        }
+    }
+}