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Tyrrx wants to merge 4 commits into from
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Add or else methods to option closes #31 #47

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86c3eaf
Add or else methods to option closes #31
Tyrrx Jan 31, 2025
1b1b451
- add test
ax0l0tl Jan 31, 2025
59f0ee2
Apply suggestion from @park-jasper
ax0l0tl Mar 10, 2026
4d13b7e
- add tests for Option Match methods
ax0l0tl Mar 10, 2026
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54 changes: 45 additions & 9 deletions Source/FunicularSwitch/Option.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand All @@ -79,6 +81,16 @@ public async Task<TResult> Match<TResult>(Func<T, Task<TResult>> some, Func<Task

return await none().ConfigureAwait(false);
}

@ax0l0tl ax0l0tl Jan 31, 2025 •
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Is this actually a breaking change? -> GetValueOrDefault...

@Tyrrx Tyrrx Jan 31, 2025

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You mean the match? In certain cases, as seen in GetValueOrDefault, it breaks the C# type inference.

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)
{
Expand All @@ -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);

Expand Down Expand Up @@ -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)
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{
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

Expand Down
200 changes: 200 additions & 0 deletions Source/Tests/FunicularSwitch.Test/OptionSpecs.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -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().Which.Should().Be(42);
}

[TestMethod]
public void QueryExpressionSelect()
{
Expand Down Expand Up @@ -217,6 +234,189 @@ public void NullOptionsWork()
nullOption.Equals(Option<MyClass?>.Some(null)).Should().BeTrue();
}

[TestMethod]
public void MatchWithActionExecutesSomeWhenSome()
{
var called = false;
Some(42).Match(x => called = x == 42);
called.Should().BeTrue();
}

[TestMethod]
public void MatchWithActionExecutesNoneWhenNone()
{
var called = false;
None<int>().Match(_ => { }, () => called = true);
called.Should().BeTrue();
}

[TestMethod]
public async Task MatchWithAsyncActionExecutesSomeWhenSome()
{
var called = false;
await Some(42).Match(
async x =>
{
await Task.Yield();
called = x == 42;
});
called.Should().BeTrue();
}

[TestMethod]
public async Task MatchWithAsyncActionExecutesNoneWhenNone()
{
var called = false;
await None<int>().Match(
async _ => await Task.Yield(),
async () =>
{
await Task.Yield();
called = true;
});
called.Should().BeTrue();
}

[TestMethod]
public void MatchWithFuncReturnsResultFromSomeWhenSome()
{
var result = Some(42).Match(x => x * 2, () => 0);
result.Should().Be(84);
}

[TestMethod]
public void MatchWithFuncReturnsResultFromNoneWhenNone()
{
var result = None<int>().Match(x => x * 2, () => 99);
result.Should().Be(99);
}

[TestMethod]
public void MatchWithValueReturnsValueWhenNone()
{
var result = None<int>().Match(x => x * 2, 99);
result.Should().Be(99);
}

[TestMethod]
public void MatchWithValueReturnsResultFromSomeWhenSome()
{
var result = Some(42).Match(x => x * 2, 0);
result.Should().Be(84);
}

[TestMethod]
public async Task MatchWithAsyncFuncBothReturnsResultFromSomeWhenSome()
{
var result = await Some(42).Match(
async x =>
{
await Task.Yield();
return x * 2;
},
async () =>
{
await Task.Yield();
return 0;
});
result.Should().Be(84);
}

[TestMethod]
public async Task MatchWithAsyncFuncBothReturnsResultFromNoneWhenNone()
{
var result = await None<int>().Match(
async x =>
{
await Task.Yield();
return x * 2;
},
async () =>
{
await Task.Yield();
return 99;
});
result.Should().Be(99);
}

[TestMethod]
public async Task MatchWithSyncSomeAsyncNoneReturnsResultFromSomeWhenSome()
{
var result = await Some(42).Match(
x => x * 2,
async () =>
{
await Task.Yield();
return 0;
});
result.Should().Be(84);
}

[TestMethod]
public async Task MatchWithSyncSomeAsyncNoneReturnsResultFromNoneWhenNone()
{
var result = await None<int>().Match(
x => x * 2,
async () =>
{
await Task.Yield();
return 99;
});
result.Should().Be(99);
}

[TestMethod]
public async Task MatchWithAsyncSomeSyncNoneReturnsResultFromSomeWhenSome()
{
var result = await Some(42).Match(
async x =>
{
await Task.Yield();
return x * 2;
},
() => 0);
result.Should().Be(84);
}

[TestMethod]
public async Task MatchWithAsyncSomeSyncNoneReturnsResultFromNoneWhenNone()
{
var result = await None<int>().Match(
async x =>
{
await Task.Yield();
return x * 2;
},
() => 99);
result.Should().Be(99);
}

[TestMethod]
public async Task MatchWithAsyncSomeValueNoneReturnsResultFromSomeWhenSome()
{
var result = await Some(42).Match(
async x =>
{
await Task.Yield();
return x * 2;
},
84);
result.Should().Be(84);
}

[TestMethod]
public async Task MatchWithAsyncSomeValueNoneReturnsResultFromNoneWhenNone()
{
var result = await None<int>().Match(
async x =>
{
await Task.Yield();
return x * 2;
},
99);
result.Should().Be(99);
}

class MyClass;

class MyOtherClass;
Expand Down