Add or else methods to option closes #31

Source/FunicularSwitch/Option.cs

@@ -48,11 +48,13 @@ public interface IOption
         public Option<T1> Bind<T1>(Func<T, Option<T1>> map) => Match(map, Option<T1>.None);
 
         public Task<Option<T1>> Bind<T1>(Func<T, Task<Option<T1>>> bind) => Match(bind, () => Option<T1>.None);
+
+        public Option<T> OrElse(Option<T> other) => OrElse(() => other);
+        public Option<T> OrElse(Func<Option<T>> other) => Match(Option.Some, other);
+        public Task<Option<T>> OrElse(Task<Option<T>> other) => OrElse(() => other);
+        public Task<Option<T>> OrElse(Func<Task<Option<T>>> other) => Match(Option.Some, other);
 
-        public void Match(Action<T> some, Action? none = null)
-        {
-            Match(some.ToFunc(), none?.ToFunc<int>() ?? (() => 42));
-        }
+        public void Match(Action<T> some, Action? none = null) => Match(some.ToFunc(), none?.ToFunc<int>() ?? (() => 42));
 
         public async Task Match(Func<T, Task> some, Func<Task>? none = null)
         {
@@ -79,6 +81,16 @@ public async Task<TResult> Match<TResult>(Func<T, Task<TResult>> some, Func<Task
 
             return await none().ConfigureAwait(false);
         }
+
+        public async Task<TResult> Match<TResult>(Func<T, TResult> some, Func<Task<TResult>> none)
+        {
+            if (_isSome)
+            {
+                return some(_value);
+            }
+
+            return await none().ConfigureAwait(false);
+        }
 
         public async Task<TResult> Match<TResult>(Func<T, Task<TResult>> some, Func<TResult> none)
         {
@@ -104,15 +116,15 @@ public async Task<TResult> Match<TResult>(Func<T, Task<TResult>> some, TResult n
 
         IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
 
-        public IEnumerator<T> GetEnumerator() => Match(v => new[] { v }, Enumerable.Empty<T>).GetEnumerator();
+        public IEnumerator<T> GetEnumerator() => Match(v => [v], Enumerable.Empty<T>).GetEnumerator();
 
-        public T? GetValueOrDefault() => Match(v => (T?)v, () => default);
+        public T? GetValueOrDefault() => Match(v => v, default(T?));
 
         public T GetValueOrDefault(Func<T> defaultValue) => Match(v => v, defaultValue);
 
         public T GetValueOrDefault(T defaultValue) => Match(v => v, () => defaultValue);
 
-        public T GetValueOrThrow(string? errorMessage = null) => Match(v => v, () => throw new InvalidOperationException(errorMessage ?? "Cannot access value of none option"));
+        public T GetValueOrThrow(string? errorMessage = null) => Match(v => v, T () => throw new InvalidOperationException(errorMessage ?? "Cannot access value of none option"));
 
         public Option<TOther> Convert<TOther>() => Match(s => Option<TOther>.Some((TOther)(object)s!), Option<TOther>.None);
 
@@ -181,22 +193,46 @@ public static async Task<Option<TOut>> Bind<T, TOut>(this Task<Option<T>> bind,
             var result = await bind.ConfigureAwait(false);
             return await result.Bind(convert).ConfigureAwait(false);
         }
+
+        public static async Task<Option<T>> OrElse<T>(this Task<Option<T>> option, Option<T> other)
+        {
+            var result = await option.ConfigureAwait(false);
+            return result.OrElse(other);
+        }
+
+        public static async Task<Option<T>> OrElse<T>(this Task<Option<T>> option, Func<Option<T>> other)
+        {
+            var result = await option.ConfigureAwait(false);
+            return result.OrElse(other);
+        }
+
+        public static async Task<Option<T>> OrElse<T>(this Task<Option<T>> option, Task<Option<T>> other)
+        {
+            var result = await option.ConfigureAwait(false);
+            return await result.OrElse(other).ConfigureAwait(false);
+        }
+
+        public static async Task<Option<T>> OrElse<T>(this Task<Option<T>> option, Func<Task<Option<T>>> other)
+        {
+            var result = await option.ConfigureAwait(false);
+            return await result.OrElse(other).ConfigureAwait(false);
+        }
 
         public static IEnumerable<TOut> Choose<T, TOut>(this IEnumerable<T> items, Func<T, Option<TOut>> choose) => items.SelectMany(i => choose(i));
 
         public static Option<T> ToOption<T>(this Result<T> result) => ToOption(result, null);
 
         public static Option<T> ToOption<T>(this Result<T> result, Action<string>? logError) =>
             result.Match(
-                ok => Option.Some(ok),
+                Option.Some,
                 error =>
                 {
                     logError?.Invoke(error);
                     return Option<T>.None;
                 });
 
         public static Result<T> ToResult<T>(this Option<T> option, Func<string> errorIfNone) =>
-            option.Match(s => Result.Ok(s), () => Result.Error<T>(errorIfNone()));
+            option.Match(Result.Ok, () => Result.Error<T>(errorIfNone()));
 
         #region query-expression pattern
 

Source/Tests/FunicularSwitch.Test/OptionSpecs.cs

@@ -49,6 +49,23 @@ public void NullCoalescingWithResultBoolBehavesAsExpected()
 		result.Should().BeError().Subject.Should().Be("Value is missing");
 	}
 
+    [TestMethod]
+    public async Task OrElse()
+    {
+        var none = None<int>();
+        none.OrElse(Option<int>.None).Should().BeNone();
+        ShouldBeSome42(none.OrElse(42));
+
+        var some = Some(42);
+        ShouldBeSome42(some.OrElse(Option<int>.None));
+        ShouldBeSome42(some.OrElse(2));
+
+        ShouldBeSome42(await none.OrElse(() => Task.FromResult(Some(42))));
+        return;
+
+        void ShouldBeSome42(Option<int> option) => option.Should().BeSome().Subject.Should().Be(42);
+    }
+
 	[TestMethod]
 	public void QueryExpressionSelect()
 	{