From 9a80bf2c1e5f9314c85dd7274e117e17f5846f2e Mon Sep 17 00:00:00 2001
From: Christopher Calmes <christopher.calmes@pacesetterclaims.com>
Date: Fri, 20 Sep 2024 14:35:55 -0500
Subject: [PATCH] added select overload with projection for result

---
 .../ResultTests/Extensions/SelectTests.cs     | 51 +++++++++++++++++++
 .../Result/Methods/Extensions/Select.cs       | 15 ++++++
 2 files changed, 66 insertions(+)
 create mode 100644 CSharpFunctionalExtensions.Tests/ResultTests/Extensions/SelectTests.cs
 create mode 100644 CSharpFunctionalExtensions/Result/Methods/Extensions/Select.cs

diff --git a/CSharpFunctionalExtensions.Tests/ResultTests/Extensions/SelectTests.cs b/CSharpFunctionalExtensions.Tests/ResultTests/Extensions/SelectTests.cs
new file mode 100644
index 00000000..ac96862b
--- /dev/null
+++ b/CSharpFunctionalExtensions.Tests/ResultTests/Extensions/SelectTests.cs
@@ -0,0 +1,51 @@
+using FluentAssertions;
+using Xunit;
+
+namespace CSharpFunctionalExtensions.Tests.ResultTests.Extensions;
+public class SelectTests
+{
+    [Fact]
+    public void Select_returns_new_result()
+    {
+        Result<MyClass> result = new MyClass { Property = "Some value" };
+
+        Result<string> result2 = result.Select(x => x.Property);
+
+        result2.IsSuccess.Should().BeTrue();
+        result2.GetValueOrDefault().Should().Be("Some value");
+    }
+
+    [Fact]
+    public void Select_returns_no_value_if_no_value_passed_in()
+    {
+        Result<MyClass> result = Result.Failure<MyClass>("error message");
+
+        Result<MyClass> result2 = result.Select(x => x);
+
+        result2.IsSuccess.Should().BeFalse();
+        result2.GetValueOrDefault().Should().Be(default);
+    }
+
+    [Fact]
+    public void Result_Error_Select_from_class_to_struct_retains_Error()
+    {
+        Result.Failure<string>("error message").Select(_ => 42).IsSuccess.Should().BeFalse();
+        Result.Failure<string>("error message").Select(_ => 42).Error.Should().Be("error message");
+    }
+
+    [Fact]
+    public void Result_can_be_used_with_linq_query_syntax()
+    {
+        Result<string> name = "John";
+
+        Result<string> upper = from x in name select x.ToUpper();
+
+        upper.IsSuccess.Should().BeTrue();
+        upper.GetValueOrDefault().Should().Be("JOHN");
+    }
+
+    private class MyClass
+    {
+        public string Property { get; set; }
+    }
+}
diff --git a/CSharpFunctionalExtensions/Result/Methods/Extensions/Select.cs b/CSharpFunctionalExtensions/Result/Methods/Extensions/Select.cs
new file mode 100644
index 00000000..a5b98853
--- /dev/null
+++ b/CSharpFunctionalExtensions/Result/Methods/Extensions/Select.cs
@@ -0,0 +1,15 @@
+using System;
+
+namespace CSharpFunctionalExtensions
+{
+    public static partial class ResultExtensions
+    {
+        /// <summary>
+        ///     This method should be used in linq queries. We recommend using Map method.
+        /// </summary>
+        public static Result<K> Select<T, K>(in this Result<T> result, Func<T, K> selector)
+        {
+            return result.Map(selector);
+        }
+    }
+}