From 827c34d2c6a7fd5a29124cff3f9f012f0abe97a9 Mon Sep 17 00:00:00 2001
From: Matthew Layton <matthew.layton@live.co.uk>
Date: Wed, 5 Jun 2024 15:40:47 +0100
Subject: [PATCH] Added `Optional.Of` to handle nullable structs.

---
 OnixLabs.Core.UnitTests/OptionalTests.cs      | 32 +++++++++++++++++++
 OnixLabs.Core/OnixLabs.Core.csproj            |  2 +-
 OnixLabs.Core/Optional.cs                     | 17 +++++++++-
 OnixLabs.Numerics/OnixLabs.Numerics.csproj    |  2 +-
 .../OnixLabs.Security.Cryptography.csproj     |  2 +-
 5 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/OnixLabs.Core.UnitTests/OptionalTests.cs b/OnixLabs.Core.UnitTests/OptionalTests.cs
index b91a3ed..6621a34 100644
--- a/OnixLabs.Core.UnitTests/OptionalTests.cs
+++ b/OnixLabs.Core.UnitTests/OptionalTests.cs
@@ -87,6 +87,38 @@ public void OptionalOfShouldProduceExpectedResultForExplicitNonDefaultValues()
         Assert.Equal("abc", text);
     }
 
+    [Fact(DisplayName = "Optional.Of should produce the expected result for null nullable struct values.")]
+    public void OptionalOfShouldProduceExpectedResultForNullNullableStructValues()
+    {
+        // Given / When
+        Optional<int> number = Optional<int>.Of((int?)null);
+        Optional<Guid> identifier = Optional<Guid>.Of((Guid?)default);
+
+        // Then
+        Assert.False(number.HasValue);
+        Assert.IsType<None<int>>(number);
+
+        Assert.False(identifier.HasValue);
+        Assert.IsType<None<Guid>>(identifier);
+    }
+
+    [Fact(DisplayName = "Optional.Of should produce the expected result for non-null nullable struct values.")]
+    public void OptionalOfShouldProduceExpectedResultForNonNullNullableStructValues()
+    {
+        // Given / When
+        Optional<int> number = Optional<int>.Of((int?)123);
+        Optional<Guid> identifier = Optional<Guid>.Of((Guid?)Guid.Empty);
+
+        // Then
+        Assert.True(number.HasValue);
+        Assert.IsType<Some<int>>(number);
+        Assert.Equal(123, number);
+
+        Assert.True(identifier.HasValue);
+        Assert.IsType<Some<Guid>>(identifier);
+        Assert.Equal(Guid.Empty, identifier);
+    }
+
     [Fact(DisplayName = "Optional.Some should produce the expected result.")]
     public void OptionalSomeShouldProduceExpectedResult()
     {
diff --git a/OnixLabs.Core/OnixLabs.Core.csproj b/OnixLabs.Core/OnixLabs.Core.csproj
index 282e8a5..121cbbe 100644
--- a/OnixLabs.Core/OnixLabs.Core.csproj
+++ b/OnixLabs.Core/OnixLabs.Core.csproj
@@ -11,7 +11,7 @@
         <NeutralLanguage>en</NeutralLanguage>
         <Copyright>Copyright © ONIXLabs 2020</Copyright>
         <RepositoryUrl>https://github.com/onix-labs/onixlabs-dotnet</RepositoryUrl>
-        <PackageVersion>8.5.0</PackageVersion>
+        <PackageVersion>8.6.0</PackageVersion>
         <PackageLicenseUrl></PackageLicenseUrl>
     </PropertyGroup>
     <PropertyGroup>
diff --git a/OnixLabs.Core/Optional.cs b/OnixLabs.Core/Optional.cs
index 2a34952..58d132b 100644
--- a/OnixLabs.Core/Optional.cs
+++ b/OnixLabs.Core/Optional.cs
@@ -53,7 +53,22 @@ internal Optional()
     /// Returns a new instance of the <see cref="Optional{T}"/> class, where the underlying value is present if
     /// the specified value is not <see langword="default"/>; otherwise, the underlying value is <see cref="None"/>.
     /// </returns>
-    public static Optional<T> Of(T? value) => value is null || EqualityComparer<T>.Default.Equals(value, default) ? None : Some(value);
+    public static Optional<T> Of(T? value) => value is not null && !EqualityComparer<T>.Default.Equals(value, default)
+        ? Some(value)
+        : None;
+
+    /// <summary>
+    /// Creates a new instance of the <see cref="Optional{T}"/> class, where the underlying value is present if
+    /// the specified value is not <see langword="null"/>; otherwise, the underlying value is <see cref="None"/>.
+    /// </summary>
+    /// <param name="value">The underlying optional value.</param>
+    /// <returns>
+    /// Returns a new instance of the <see cref="Optional{T}"/> class, where the underlying value is present if
+    /// the specified value is not <see langword="null"/>; otherwise, the underlying value is <see cref="None"/>.
+    /// </returns>
+    public static Optional<TStruct> Of<TStruct>(TStruct? value) where TStruct : struct => value.HasValue
+        ? Optional<TStruct>.Some(value.Value)
+        : Optional<TStruct>.None;
 
     /// <summary>
     /// Creates a new instance of the <see cref="Optional{T}"/> class, where the underlying value is present if
diff --git a/OnixLabs.Numerics/OnixLabs.Numerics.csproj b/OnixLabs.Numerics/OnixLabs.Numerics.csproj
index 0284c71..543ac47 100644
--- a/OnixLabs.Numerics/OnixLabs.Numerics.csproj
+++ b/OnixLabs.Numerics/OnixLabs.Numerics.csproj
@@ -10,7 +10,7 @@
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <Copyright>Copyright © ONIXLabs 2020</Copyright>
         <RepositoryUrl>https://github.com/onix-labs/onixlabs-dotnet</RepositoryUrl>
-        <PackageVersion>8.5.0</PackageVersion>
+        <PackageVersion>8.6.0</PackageVersion>
         <LangVersion>12</LangVersion>
         <PackageLicenseUrl></PackageLicenseUrl>
     </PropertyGroup>
diff --git a/OnixLabs.Security.Cryptography/OnixLabs.Security.Cryptography.csproj b/OnixLabs.Security.Cryptography/OnixLabs.Security.Cryptography.csproj
index ccb9af2..83ef887 100644
--- a/OnixLabs.Security.Cryptography/OnixLabs.Security.Cryptography.csproj
+++ b/OnixLabs.Security.Cryptography/OnixLabs.Security.Cryptography.csproj
@@ -10,7 +10,7 @@
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <Copyright>Copyright © ONIXLabs 2020</Copyright>
         <RepositoryUrl>https://github.com/onix-labs/onixlabs-dotnet</RepositoryUrl>
-        <PackageVersion>8.5.0</PackageVersion>
+        <PackageVersion>8.6.0</PackageVersion>
         <LangVersion>12</LangVersion>
         <PackageLicenseUrl></PackageLicenseUrl>
     </PropertyGroup>