Add implicit conversion to PageConnection from Page (#9806)

Author: michaelstaib

src/HotChocolate/Core/src/Types.CursorPagination.Extensions/PageConnection.cs

@@ -77,4 +77,13 @@ public override IReadOnlyList<PageEdge<TNode>>? Edges
     /// </summary>
     [GraphQLDescription("Identifies the total count of items in the connection.")]
     public int TotalCount => _page.TotalCount ?? -1;
+
+    /// <summary>
+    /// Converts a <see cref="Page{TNode}"/> to a <see cref="PageConnection{TNode}"/>.
+    /// </summary>
+    /// <param name="page">
+    /// The page to convert.
+    /// </param>
+    public static implicit operator PageConnection<TNode>(Page<TNode> page)
+        => new(page);
 }

src/HotChocolate/Core/test/Types.CursorPagination.Tests/PageConnectionTests.cs

@@ -0,0 +1,40 @@
+using GreenDonut.Data;
+
+namespace HotChocolate.Types.Pagination;
+
+public class PageConnectionTests
+{
+    [Fact]
+    public void ImplicitConversion_Should_WrapPage_When_ConvertingPageToConnection()
+    {
+        // arrange
+        var page = Page<string>.Create(
+            ["a", "b", "c"],
+            hasNextPage: true,
+            hasPreviousPage: false,
+            item => item,
+            totalCount: 10);
+
+        // act
+        PageConnection<string> connection = page;
+
+        // assert
+        Assert.Same(page, connection.Nodes);
+        Assert.Equal(10, connection.TotalCount);
+        Assert.Equal(3, connection.Edges!.Count);
+        Assert.True(connection.PageInfo.HasNextPage);
+    }
+
+    [Fact]
+    public void ImplicitConversion_Should_ThrowArgumentNullException_When_PageIsNull()
+    {
+        // arrange
+        Page<string>? page = null;
+
+        // act
+        PageConnection<string> Convert() => page!;
+
+        // assert
+        Assert.Throws<ArgumentNullException>(Convert);
+    }
+}