Add allocation-free Maybe.Bind overload

CSharpFunctionalExtensions.Tests/MaybeTests/Extensions/BindTests.cs

@@ -1,39 +1,97 @@
-using FluentAssertions;
-using Xunit;
-
-namespace CSharpFunctionalExtensions.Tests.MaybeTests.Extensions
-{
-    public class BindTests : MaybeTestBase
-    {
-        [Fact]
-        public void Bind_returns_no_value_if_initial_maybe_is_null()
-        {
-            Maybe<T> maybe = null;
-
-            var maybe2 = maybe.Bind(ExpectAndReturnMaybe(null, T.Value));
-
-            maybe2.HasValue.Should().BeFalse();
-        }
-
-        [Fact]
-        public void Bind_returns_no_value_if_selector_returns_null()
-        {
-            Maybe<T> maybe = T.Value;
-
-            var maybe2 = maybe.Bind(ExpectAndReturn(T.Value, Maybe<T>.None));
-
-            maybe2.HasValue.Should().BeFalse();
-        }
-
-        [Fact]
-        public void Bind_returns_value_if_selector_returns_value()
-        {
-            Maybe<T> maybe = T.Value;
-
-            var maybe2 = maybe.Bind(ExpectAndReturnMaybe<T>(T.Value, T.Value));
-
-            maybe2.HasValue.Should().BeTrue();
-            maybe2.Value.Should().Be(T.Value);
-        }
-    }
-}
+using FluentAssertions;
+using Xunit;
+
+namespace CSharpFunctionalExtensions.Tests.MaybeTests.Extensions
+{
+    public class BindTests : MaybeTestBase
+    {
+        [Fact]
+        public void Bind_returns_no_value_if_initial_maybe_is_null()
+        {
+            Maybe<T> maybe = null;
+
+            var maybe2 = maybe.Bind(ExpectAndReturnMaybe(null, T.Value));
+
+            maybe2.HasValue.Should().BeFalse();
+        }
+
+        [Fact]
+        public void Bind_returns_no_value_if_selector_returns_null()
+        {
+            Maybe<T> maybe = T.Value;
+
+            var maybe2 = maybe.Bind(ExpectAndReturn(T.Value, Maybe<T>.None));
+
+            maybe2.HasValue.Should().BeFalse();
+        }
+
+        [Fact]
+        public void Bind_returns_value_if_selector_returns_value()
+        {
+            Maybe<T> maybe = T.Value;
+
+            var maybe2 = maybe.Bind(ExpectAndReturnMaybe<T>(T.Value, T.Value));
+
+            maybe2.HasValue.Should().BeTrue();
+            maybe2.Value.Should().Be(T.Value);
+        }
+
+        [Fact]
+        public void Bind_provides_context_to_selector()
+        {
+            Maybe<T> maybe = null;
+            var context = 5;
+
+            var maybe2 = maybe.Bind(
+                (value, ctx) =>
+                {
+                    ctx.Should().Be(context);
+                    return Maybe.From(value);
+                },
+                context
+            );
+
+            maybe2.HasValue.Should().BeFalse();
+        }
+
+        [Fact]
+        public void Bind_with_context_returns_no_value_if_initial_maybe_is_null()
+        {
+            Maybe<T> maybe = null;
+
+            var maybe2 = maybe.Bind(
+                (value, _) => ExpectAndReturnMaybe(null, T.Value)(value),
+                context: 5
+            );
+
+            maybe2.HasValue.Should().BeFalse();
+        }
+
+        [Fact]
+        public void Bind_with_context_returns_no_value_if_selector_returns_null()
+        {
+            Maybe<T> maybe = T.Value;
+
+            var maybe2 = maybe.Bind(
+                (value, _) => ExpectAndReturn(T.Value, Maybe<T>.None)(value),
+                context: 5
+            );
+
+            maybe2.HasValue.Should().BeFalse();
+        }
+
+        [Fact]
+        public void Bind_with_context_returns_value_if_selector_returns_value()
+        {
+            Maybe<T> maybe = T.Value;
+
+            var maybe2 = maybe.Bind(
+                (value, _) => ExpectAndReturnMaybe<T>(T.Value, T.Value)(value),
+                5
+            );
+
+            maybe2.HasValue.Should().BeTrue();
+            maybe2.Value.Should().Be(T.Value);
+        }
+    }
+}

CSharpFunctionalExtensions/Maybe/Extensions/Bind.cs

@@ -1,15 +1,27 @@
-using System;
-
-namespace CSharpFunctionalExtensions
-{
-    public static partial class MaybeExtensions
-    {
-        public static Maybe<K> Bind<T, K>(in this Maybe<T> maybe, Func<T, Maybe<K>> selector)
-        {
-            if (maybe.HasNoValue)
-                return Maybe<K>.None;
-
-            return selector(maybe.GetValueOrThrow());
-        }
-    }
-}
+using System;
+
+namespace CSharpFunctionalExtensions
+{
+    public static partial class MaybeExtensions
+    {
+        public static Maybe<K> Bind<T, K>(in this Maybe<T> maybe, Func<T, Maybe<K>> selector)
+        {
+            if (maybe.HasNoValue)
+                return Maybe<K>.None;
+
+            return selector(maybe.GetValueOrThrow());
+        }
+
+        public static Maybe<K> Bind<T, K, TContext>(
+            in this Maybe<T> maybe,
+            Func<T, TContext, Maybe<K>> selector,
+            TContext context
+        )
+        {
+            if (maybe.HasNoValue)
+                return Maybe<K>.None;
+
+            return selector(maybe.GetValueOrThrow(), context);
+        }
+    }
+}