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improve result structure and handling

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This commit is contained in:
Oli Sturm
2026-05-04 19:39:49 +01:00
parent 0d02927ba6
commit 73ed4c7b9c
14 changed files with 413 additions and 371 deletions
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csharp-fp3.Tests/ResultTests.cs
+68 -67
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@@ -1,4 +1,5 @@
using CsharpFp3.Library;
using static CsharpFp3.Library.ResultModule;
namespace CsharpFp3.Tests;
@@ -10,7 +11,7 @@ public class ResultTests
[Fact]
public void Ok_is_success()
{
var result = Result<int, string>.Ok(42);
Result<int, string> result = new ResultOk<int, string>(42);
Assert.True(result.IsSuccess);
Assert.False(result.IsFailure);
@@ -19,42 +20,26 @@ public class ResultTests
[Fact]
public void Fail_is_failure()
{
var result = Result<int, string>.Fail("oops");
Result<int, string> result = new ResultFail<int, string>("oops");
Assert.True(result.IsFailure);
Assert.False(result.IsSuccess);
}
[Fact]
public void Ok_exposes_value()
public void Ok_exposes_value_via_Match()
{
var result = Result<int, string>.Ok(42);
Result<int, string> result = new ResultOk<int, string>(42);
Assert.Equal(42, result.Value);
Assert.Equal(42, result.Match(v => v, _ => 0));
}
[Fact]
public void Fail_exposes_error()
public void Fail_exposes_error_via_Match()
{
var result = Result<int, string>.Fail("oops");
Result<int, string> result = new ResultFail<int, string>("oops");
Assert.Equal("oops", result.Error);
}
[Fact]
public void Accessing_Value_on_a_failed_result_throws()
{
var result = Result<int, string>.Fail("oops");
Assert.Throws<InvalidOperationException>(() => result.Value);
}
[Fact]
public void Accessing_Error_on_a_successful_result_throws()
{
var result = Result<int, string>.Ok(42);
Assert.Throws<InvalidOperationException>(() => result.Error);
Assert.Equal("oops", result.Match(_ => "", e => e));
}
// --- Match ---
@@ -62,7 +47,7 @@ public class ResultTests
[Fact]
public void Match_calls_onSuccess_for_Ok()
{
var result = Result<int, string>.Ok(10);
Result<int, string> result = new ResultOk<int, string>(10);
var output = result.Match(v => $"value:{v}", e => $"error:{e}");
@@ -72,7 +57,7 @@ public class ResultTests
[Fact]
public void Match_calls_onFailure_for_Fail()
{
var result = Result<int, string>.Fail("bad");
Result<int, string> result = new ResultFail<int, string>("bad");
var output = result.Match(v => $"value:{v}", e => $"error:{e}");
@@ -84,7 +69,7 @@ public class ResultTests
[Fact]
public void Switch_calls_onSuccess_for_Ok()
{
var result = Result<int, string>.Ok(7);
Result<int, string> result = new ResultOk<int, string>(7);
var called = false;
result.Switch(_ => called = true, _ => { });
@@ -95,7 +80,7 @@ public class ResultTests
[Fact]
public void Switch_calls_onFailure_for_Fail()
{
var result = Result<int, string>.Fail("err");
Result<int, string> result = new ResultFail<int, string>("err");
var called = false;
result.Switch(_ => { }, _ => called = true);
@@ -111,7 +96,7 @@ public class ResultTests
var result = Result<int, string>.Catch(() => 99, ex => ex.Message);
Assert.True(result.IsSuccess);
Assert.Equal(99, result.Value);
Assert.Equal(99, result.Match(v => v, _ => 0));
}
[Fact]
@@ -123,7 +108,7 @@ public class ResultTests
);
Assert.True(result.IsFailure);
Assert.Equal("boom", result.Error);
Assert.Equal("boom", result.Match(_ => "", e => e));
}
// --- Bind ---
@@ -131,33 +116,34 @@ public class ResultTests
[Fact]
public void Bind_chains_to_the_next_result_on_success()
{
var result = Result<int, string>.Ok(5).Bind(v => Result<string, string>.Ok($"got {v}"));
Result<int, string> result = new ResultOk<int, string>(5);
var chained = result.Bind(v => new ResultOk<string, string>($"got {v}"));
Assert.Equal("got 5", result.Value);
Assert.Equal("got 5", chained.Match(v => v, _ => ""));
}
[Fact]
public void Bind_short_circuits_on_failure_without_calling_the_binder()
{
var binderCalled = false;
var result = Result<int, string>
.Fail("nope")
.Bind(v =>
{
binderCalled = true;
return Result<string, string>.Ok($"got {v}");
});
Result<int, string> result = new ResultFail<int, string>("nope");
var chained = result.Bind(v =>
{
binderCalled = true;
return new ResultOk<string, string>($"got {v}");
});
Assert.False(binderCalled);
Assert.Equal("nope", result.Error);
Assert.Equal("nope", chained.Match(_ => "", e => e));
}
[Fact]
public void Bind_propagates_the_inner_failure_when_the_binder_returns_Fail()
{
var result = Result<int, string>.Ok(5).Bind(_ => Result<string, string>.Fail("inner fail"));
Result<int, string> result = new ResultOk<int, string>(5);
var chained = result.Bind(_ => new ResultFail<string, string>("inner fail"));
Assert.Equal("inner fail", result.Error);
Assert.Equal("inner fail", chained.Match(_ => "", e => e));
}
// --- Map ---
@@ -165,23 +151,25 @@ public class ResultTests
[Fact]
public void Map_transforms_the_value_on_success()
{
var result = Result<int, string>.Ok(3).Map(v => v * 2);
Result<int, string> result = new ResultOk<int, string>(3);
var mapped = result.Map(v => v * 2);
Assert.Equal(6, result.Value);
Assert.Equal(6, mapped.Match(v => v, _ => 0));
}
[Fact]
public void Map_does_not_call_the_mapper_on_failure()
{
var mapperCalled = false;
var result = Result<int, string>.Fail("err").Map(v =>
Result<int, string> result = new ResultFail<int, string>("err");
var mapped = result.Map(v =>
{
mapperCalled = true;
return v * 2;
});
Assert.False(mapperCalled);
Assert.Equal("err", result.Error);
Assert.Equal("err", mapped.Match(_ => "", e => e));
}
// --- Tap ---
@@ -190,17 +178,19 @@ public class ResultTests
public void Tap_calls_the_action_and_returns_the_original_result_on_success()
{
var seen = -1;
var result = Result<int, string>.Ok(8).Tap(v => seen = v);
Result<int, string> result = new ResultOk<int, string>(8);
var tapped = result.Tap(v => seen = v);
Assert.Equal(8, seen);
Assert.Equal(8, result.Value);
Assert.Equal(8, tapped.Match(v => v, _ => 0));
}
[Fact]
public void Tap_does_not_call_the_action_on_failure()
{
var called = false;
Result<int, string>.Fail("err").Tap(_ => called = true);
Result<int, string> result = new ResultFail<int, string>("err");
result.Tap(_ => called = true);
Assert.False(called);
}
@@ -211,17 +201,19 @@ public class ResultTests
public void TapError_calls_the_action_and_returns_the_original_result_on_failure()
{
var seen = "";
var result = Result<int, string>.Fail("bad").TapError(e => seen = e);
Result<int, string> result = new ResultFail<int, string>("bad");
var tapped = result.TapError(e => seen = e);
Assert.Equal("bad", seen);
Assert.Equal("bad", result.Error);
Assert.Equal("bad", tapped.Match(_ => "", e => e));
}
[Fact]
public void TapError_does_not_call_the_action_on_success()
{
var called = false;
Result<int, string>.Ok(1).TapError(_ => called = true);
Result<int, string> result = new ResultOk<int, string>(1);
result.TapError(_ => called = true);
Assert.False(called);
}
@@ -231,23 +223,25 @@ public class ResultTests
[Fact]
public void MapError_transforms_the_error_on_failure()
{
var result = Result<int, string>.Fail("oops").MapError(e => e.Length);
Result<int, string> result = new ResultFail<int, string>("oops");
var mapped = result.MapError(e => e.Length);
Assert.Equal(4, result.Error);
Assert.Equal(4, mapped.Match(_ => 0, e => e));
}
[Fact]
public void MapError_does_not_call_the_mapper_on_success()
{
var mapperCalled = false;
var result = Result<int, string>.Ok(1).MapError(e =>
Result<int, string> result = new ResultOk<int, string>(1);
var mapped = result.MapError(e =>
{
mapperCalled = true;
return e.Length;
});
Assert.False(mapperCalled);
Assert.Equal(1, result.Value);
Assert.Equal(1, mapped.Match(v => v, _ => 0));
}
// --- Select / SelectMany (LINQ support) ---
@@ -255,41 +249,48 @@ public class ResultTests
[Fact]
public void Select_is_equivalent_to_Map()
{
var result = Result<int, string>.Ok(4).Select(v => v + 1);
Result<int, string> result = new ResultOk<int, string>(4);
var selected = result.Select(v => v + 1);
Assert.Equal(5, result.Value);
Assert.Equal(5, selected.Match(v => v, _ => 0));
}
[Fact]
public void SelectMany_sequences_two_successful_results()
{
Result<int, string> aResult = new ResultOk<int, string>(3);
Result<int, string> bResult = new ResultOk<int, string>(4);
var result =
from a in Result<int, string>.Ok(3)
from b in Result<int, string>.Ok(4)
from a in aResult
from b in bResult
select a + b;
Assert.Equal(7, result.Value);
Assert.Equal(7, result.Match(v => v, _ => 0));
}
[Fact]
public void SelectMany_short_circuits_when_the_first_result_fails()
{
Result<int, string> aResult = new ResultFail<int, string>("first fail");
Result<int, string> bResult = new ResultOk<int, string>(4);
var result =
from a in Result<int, string>.Fail("first fail")
from b in Result<int, string>.Ok(4)
from a in aResult
from b in bResult
select a + b;
Assert.Equal("first fail", result.Error);
Assert.Equal("first fail", result.Match(_ => "", e => e));
}
[Fact]
public void SelectMany_short_circuits_when_the_second_result_fails()
{
Result<int, string> aResult = new ResultOk<int, string>(3);
Result<int, string> bResult = new ResultFail<int, string>("second fail");
var result =
from a in Result<int, string>.Ok(3)
from b in Result<int, string>.Fail("second fail")
from a in aResult
from b in bResult
select a + b;
Assert.Equal("second fail", result.Error);
Assert.Equal("second fail", result.Match(_ => "", e => e));
}
}