Added CollectionSegment<T> (#3597)

src/HotChocolate/Core/src/Types.OffsetPagination/CollectionSegment.cs

@@ -6,7 +6,7 @@
 namespace HotChocolate.Types.Pagination
 {
     /// <summary>
-    /// The collection segment represents one page of a pagebale data set / collection.
+    /// The collection segment represents one page of a pageable dataset / collection.
     /// </summary>
     public class CollectionSegment : IPage
     {
@@ -31,7 +31,8 @@ public class CollectionSegment : IPage
         {
             Items = items ??
                 throw new ArgumentNullException(nameof(items));
-            Info = info;
+            Info = info ??
+                throw new ArgumentNullException(nameof(info));
             _getTotalCount = getTotalCount ??
                 throw new ArgumentNullException(nameof(getTotalCount));
         }

src/HotChocolate/Core/src/Types.OffsetPagination/CollectionSegment~1.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace HotChocolate.Types.Pagination
+{
+    /// <inheritdoc />
+    public class CollectionSegment<T> : CollectionSegment
+        where T : class
+    {
+        /// <summary>
+        /// Initializes <see cref="CollectionSegment" />.
+        /// </summary>
+        /// <param name="items">
+        /// The items that belong to this page.
+        /// </param>
+        /// <param name="info">
+        /// Additional information about this page.
+        /// </param>
+        /// <param name="getTotalCount">
+        /// A delegate to request the the total count.
+        /// </param>
+        public CollectionSegment(
+            IReadOnlyCollection<T> items,
+            CollectionSegmentInfo info,
+            Func<CancellationToken, ValueTask<int>> getTotalCount)
+            : base(items, info, getTotalCount)
+        {
+            Items = items;
+        }
+
+        /// <summary>
+        /// The items that belong to this page.
+        /// </summary>
+        public new IReadOnlyCollection<T> Items { get; }
+    }
+}

src/HotChocolate/Core/test/Types.OffsetPagination.Tests/CollectionSegmentTests.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using Xunit;
+
+namespace HotChocolate.Types.Pagination
+{
+    public class CollectionSegmentTests
+    {
+        [Fact]
+        public void CreateCollectionSegment_PageInfoAndItems_PassedCorrectly()
+        {
+            // arrange
+            var pageInfo = new CollectionSegmentInfo(true, true);
+            var items = new List<string>();
+
+            // act
+            var collection = new CollectionSegment(
+                items,
+                pageInfo,
+                ct => throw new NotSupportedException());
+
+            // assert
+            Assert.Equal(pageInfo, collection.Info);
+            Assert.Equal(items, collection.Items);
+        }
+
+        [Fact]
+        public void CreateCollectionSegment_PageInfoNull_ArgumentNullException()
+        {
+            // arrange
+            var items = new List<string>();
+
+            // act
+            Action a = () => new CollectionSegment<string>(
+                items, null, ct => throw new NotSupportedException());
+
+            // assert
+            Assert.Throws<ArgumentNullException>(a);
+        }
+
+        [Fact]
+        public void CreateCollectionSegment_ItemsNull_ArgumentNullException()
+        {
+            // arrange
+            var pageInfo = new CollectionSegmentInfo(true, true);
+
+            // act
+            Action a = () => new CollectionSegment<string>(
+                null, pageInfo, ct => throw new NotSupportedException());
+
+            // assert
+            Assert.Throws<ArgumentNullException>(a);
+        }
+    }
+}

src/HotChocolate/Core/test/Types.OffsetPagination.Tests/CustomCollectionSegmentHandlerTests.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Threading.Tasks;
+using HotChocolate.Execution;
+using HotChocolate.Tests;
+using Snapshooter.Xunit;
+using Xunit;
+
+namespace HotChocolate.Types.Pagination
+{
+    public class CustomCollectionSegmentHandlerTests
+    {
+        [Fact]
+        public void Infer_Schema_Correctly_When_CollectionSegment_IsUsed()
+        {
+            SchemaBuilder.New()
+                .AddQueryType<Query>()
+                .Create()
+                .Print()
+                .MatchSnapshot();
+        }
+
+        [Fact]
+        public async Task Use_Resolver_Result_If_It_Is_A_Page()
+        {
+            // arrange
+            Snapshot.FullName();
+
+            IReadOnlyQueryRequest request =
+                QueryRequestBuilder.New()
+                    .SetQuery("{ items { items } }")
+                    .Create();
+
+            // act
+            // assert
+            await SchemaBuilder.New()
+                .AddQueryType<Query>()
+                .Create()
+                .MakeExecutable()
+                .ExecuteAsync(request)
+                .MatchSnapshotAsync();
+        }
+
+        public class Query
+        {
+            [UseOffsetPaging]
+            public CollectionSegment<string> GetItems(int skip, int take)
+            {
+                return new CollectionSegment<string>(
+                    new[] { "hello", "abc" },
+                    new CollectionSegmentInfo(false, false),
+                    ct => throw new NotImplementedException());
+            }
+        }
+    }
+}

src/HotChocolate/Core/test/Types.OffsetPagination.Tests/__snapshots__/CustomCollectionSegmentHandlerTests.Infer_Schema_Correctly_When_CollectionSegment_IsUsed.snap

@@ -0,0 +1,27 @@
+schema {
+  query: Query
+}
+
+"Information about the offset pagination."
+type CollectionSegmentInfo {
+  "Indicates whether more items exist following the set defined by the clients arguments."
+  hasNextPage: Boolean!
+  "Indicates whether more items exist prior the set defined by the clients arguments."
+  hasPreviousPage: Boolean!
+}
+
+type Query {
+  items(skip: Int take: Int): StringCollectionSegment
+}
+
+type StringCollectionSegment {
+  items: [String]
+  "Information to aid in pagination."
+  pageInfo: CollectionSegmentInfo!
+}
+
+"The `@defer` directive may be provided for fragment spreads and inline fragments to inform the executor to delay the execution of the current fragment to indicate deprioritization of the current fragment. A query with `@defer` directive will cause the request to potentially return multiple responses, where non-deferred data is delivered in the initial response and data deferred is delivered in a subsequent response. `@include` and `@skip` take precedence over `@defer`."
+directive @defer("If this argument label has a value other than null, it will be passed on to the result of this defer directive. This label is intended to give client applications a way to identify to which fragment a deferred result belongs to." label: String "Deferred when true." if: Boolean) on FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+"The `@stream` directive may be provided for a field of `List` type so that the backend can leverage technology such as asynchronous iterators to provide a partial list in the initial response, and additional list items in subsequent responses. `@include` and `@skip` take precedence over `@stream`."
+directive @stream("If this argument label has a value other than null, it will be passed on to the result of this stream directive. This label is intended to give client applications a way to identify to which fragment a streamed result belongs to." label: String "The initial elements that shall be send down to the consumer." initialCount: Int! "Streamed when true." if: Boolean!) on FIELD

src/HotChocolate/Core/test/Types.OffsetPagination.Tests/__snapshots__/CustomCollectionSegmentHandlerTests.Use_Resolver_Result_If_It_Is_A_Page.snap

@@ -0,0 +1,10 @@
+{
+  "data": {
+    "items": {
+      "items": [
+        "hello",
+        "abc"
+      ]
+    }
+  }
+}