fix: preserve non-null collection result payloads

Author: KSemenenko

ManagedCode.Communication.Tests/Results/ResultSuccessValueContractTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Text.Json;
+using ManagedCode.Communication.CollectionResultT;
 using Shouldly;
 
 namespace ManagedCode.Communication.Tests.Results;
@@ -57,6 +58,23 @@ public void Failure_WithNullPayload_PreservesFailure()
         result.Problem.ShouldNotBeNull();
     }
 
+    [Test]
+    public void CollectionSuccess_WithNullInitializer_PreservesEmptyNonNullCollection()
+    {
+        var result = CollectionResult<string>.Succeed(Array.Empty<string>()) with { Collection = null! };
+        result.IsSuccess.ShouldBeTrue();
+        result.Collection.ShouldBeEmpty();
+        result.Value.ShouldBeSameAs(result.Collection);
+    }
+
+    [Test]
+    public void CollectionSuccess_FromDefaultStruct_PreservesNonNullCollection()
+    {
+        var result = default(CollectionResult<string>) with { IsSuccess = true };
+        result.Collection.ShouldBeEmpty();
+        result.Value.ShouldBeSameAs(result.Collection);
+    }
+
     [Test]
     public void Deserialize_WithNullSuccessPayload_RejectsInvalidResult()
     {

ManagedCode.Communication/CollectionResultT/CollectionResult.cs

@@ -17,6 +17,8 @@ namespace ManagedCode.Communication.CollectionResultT;
 [DebuggerDisplay("IsSuccess: {IsSuccess}; Count: {Collection?.Length ?? 0}; Problem: {Problem?.Title}")]
 public partial struct CollectionResult<T> : IResultCollection<T>, ICollectionResultFactory<CollectionResult<T>, T>
 {
+    private T[]? _collection;
+
     private CollectionResult(bool isSuccess, IEnumerable<T>? collection, int pageNumber, int pageSize, int totalItems, Problem? problem) : this(
         isSuccess, collection?.ToArray(), pageNumber, pageSize, totalItems, problem)
     {
@@ -70,7 +72,11 @@ internal static CollectionResult<T> CreateFailed(Problem problem, T[]? collectio
     [JsonPropertyName(CommunicationJsonNames.Collection)]
     [JsonPropertyOrder(2)]
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
-    public T[] Collection { get; init; } = [];
+    public T[] Collection
+    {
+        get => _collection ?? [];
+        init => _collection = value;
+    }
 
     /// <summary>
     ///     Gets the collection as a Value property, for <see cref="IResult{T}" /> compatibility.

README.md

@@ -125,6 +125,8 @@ replacing a successful payload with null in an initializer, throws `ArgumentNull
 C# type argument does not allow a successful null payload. `Result<int>.Succeed()` still carries zero,
 while `Result<string>.Succeed()` has no valid default payload and throws. For an operation with no
 data, return `Result.Succeed()`; for optional data, return a real value or an appropriate failure.
+`CollectionResult<T>.Collection` always exposes a non-null collection, including default struct values
+and null initializer input; missing collections normalize to empty, matching its existing factories.
 
 `Result` and `Result<T>` are structs. Their state is fixed after construction, but referenced payloads and
 `Problem` objects remain mutable. Avoid changing a shared problem after returning or publishing it.