Fix issue with Query Planner ExecutionStep Requirements

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/RequirementsPlannerMiddleware.cs

@@ -64,7 +64,9 @@ currentStep.ParentSelection is { } parent &&
                         roots.Add(siblingExecutionStep.SubgraphName);
                     }
 
-                    schemas.TryAdd(siblingExecutionStep.SubgraphName, siblingExecutionStep);
+                    // Tracks the most recent execution step (by query plan step order) targeting a given subgraph
+                    // Replacing a previous execution step if necessary. 
+                    schemas[siblingExecutionStep.SubgraphName] = siblingExecutionStep;
                 }
 
                 // clean and fill requires set
@@ -94,7 +96,7 @@ currentStep.ParentSelection is { } parent &&
                 // already depends on.
                 var variables = OrderByUsage(step.SelectionSetTypeMetadata.Variables, currentStep);
 
-                // if we have root steps as siblings we will prfer to fulfill the requirements
+                // if we have root steps as siblings we will prefer to fulfill the requirements
                 // from these steps.
                 if (roots.Count > 0 && requires.Count > 0)
                 {

src/HotChocolate/Fusion/test/Core.Tests/RequestPlannerTests.cs

@@ -1057,6 +1057,46 @@ query TopProducts {
         await snapshot.MatchAsync();
     }
 
+    [Fact]
+    public async Task Query_Plan_27_Multiple_Require_Steps_From_Same_Subgraph()
+    {
+        // arrange
+        using var demoProject = await DemoProject.CreateAsync();
+
+        var fusionGraph = await FusionGraphComposer.ComposeAsync(
+            new[]
+            {
+                demoProject.Authors.ToConfiguration(),
+                demoProject.Books.ToConfiguration()
+            });
+
+        // act
+        var result = await CreateQueryPlanAsync(
+            fusionGraph,
+            """
+            query Query {
+                authorById(id: "1") {
+                    id,
+                    name,
+                    bio,
+                    books {
+                        id
+                        author {
+                            books {
+                                id
+                            }
+                        }
+                    }
+                }
+            }
+            """);
+
+        var snapshot = new Snapshot();
+        snapshot.Add(result.UserRequest, nameof(result.UserRequest));
+        snapshot.Add(result.QueryPlan, nameof(result.QueryPlan));
+        await snapshot.MatchAsync();
+    }
+
     private static async Task<(DocumentNode UserRequest, Execution.Nodes.QueryPlan QueryPlan)> CreateQueryPlanAsync(
         Skimmed.Schema fusionGraph,
         [StringSyntax("graphql")] string query)

src/HotChocolate/Fusion/test/Core.Tests/__snapshots__/RequestPlannerTests.Query_Plan_18_Node_Single_Fragment_Multiple_Subgraphs.snap

@@ -50,7 +50,7 @@ QueryPlan
             "node": {
               "type": "Resolve",
               "subgraph": "Reviews2",
-              "document": "query FetchNode_2($id: ID!) { node(id: $id) { ... on User { reviews { body } __typename } } }",
+              "document": "query FetchNode_2($id: ID!) { node(id: $id) { ... on User { reviews { body } __fusion_exports__2: id __typename } } }",
               "selectionSetId": 0,
               "forwardedVariables": [
                 {

src/HotChocolate/Fusion/test/Core.Tests/__snapshots__/RequestPlannerTests.Query_Plan_27_Multiple_Require_Steps_From_Same_Subgraph.snap

@@ -0,0 +1,121 @@
+UserRequest
+---------------
+query Query {
+  authorById(id: "1") {
+    id
+    name
+    bio
+    books {
+      id
+      author {
+        books {
+          id
+        }
+      }
+    }
+  }
+}
+---------------
+
+QueryPlan
+---------------
+{
+  "document": "query Query { authorById(id: \u00221\u0022) { id name bio books { id author { books { id } } } } }",
+  "operation": "Query",
+  "rootNode": {
+    "type": "Sequence",
+    "nodes": [
+      {
+        "type": "Resolve",
+        "subgraph": "Authors",
+        "document": "query Query_1 { authorById(id: \u00221\u0022) { id name bio __fusion_exports__1: id } }",
+        "selectionSetId": 0,
+        "provides": [
+          {
+            "variable": "__fusion_exports__1"
+          },
+          {
+            "variable": "__fusion_exports__2"
+          }
+        ]
+      },
+      {
+        "type": "Compose",
+        "selectionSetIds": [
+          0
+        ]
+      },
+      {
+        "type": "Parallel",
+        "nodes": [
+          {
+            "type": "Resolve",
+            "subgraph": "Books",
+            "document": "query Query_2($__fusion_exports__1: String!) { authorById(id: $__fusion_exports__1) { books { id } } }",
+            "selectionSetId": 1,
+            "path": [
+              "authorById"
+            ],
+            "requires": [
+              {
+                "variable": "__fusion_exports__1"
+              }
+            ]
+          },
+          {
+            "type": "Resolve",
+            "subgraph": "Authors",
+            "document": "query Query_3($__fusion_exports__2: String!) { bookByAuthorId(authorId: $__fusion_exports__2) { author { __fusion_exports__3: id } } }",
+            "selectionSetId": 2,
+            "path": [
+              "bookByAuthorId"
+            ],
+            "requires": [
+              {
+                "variable": "__fusion_exports__2"
+              }
+            ],
+            "provides": [
+              {
+                "variable": "__fusion_exports__3"
+              }
+            ]
+          }
+        ]
+      },
+      {
+        "type": "Compose",
+        "selectionSetIds": [
+          1,
+          2
+        ]
+      },
+      {
+        "type": "Resolve",
+        "subgraph": "Books",
+        "document": "query Query_4($__fusion_exports__3: String!) { authorById(id: $__fusion_exports__3) { books { id } } }",
+        "selectionSetId": 3,
+        "path": [
+          "authorById"
+        ],
+        "requires": [
+          {
+            "variable": "__fusion_exports__3"
+          }
+        ]
+      },
+      {
+        "type": "Compose",
+        "selectionSetIds": [
+          3
+        ]
+      }
+    ]
+  },
+  "state": {
+    "__fusion_exports__1": "Author_id",
+    "__fusion_exports__2": "Book_authorId",
+    "__fusion_exports__3": "Author_id"
+  }
+}
+---------------

src/HotChocolate/Fusion/test/Shared/Authors/Author.cs

@@ -0,0 +1,16 @@
+namespace HotChocolate.Fusion.Shared.Authors;
+
+public class Author
+{
+    public string Id { get; set;}
+
+    public string Name { get; set; }
+
+    public string Bio { get; set;}
+
+    public Author(string id, string name, string bio) {
+        this.Id = id;
+        this.Name = name;
+        this.Bio = bio;
+    }
+}

src/HotChocolate/Fusion/test/Shared/Authors/AuthorQuery.cs

@@ -0,0 +1,20 @@
+namespace HotChocolate.Fusion.Shared.Authors;
+
+[GraphQLName("Query")]
+public sealed class AuthorQuery
+{
+    public Author? AuthorById(
+        string id,
+        [Service] AuthorRepository repository)
+        => repository.GetAuthorById(id);
+
+    public IEnumerable<Author> Authors(int limit, [Service] AuthorRepository repository) 
+        => repository.GetAuthors(limit);
+
+    public Book BookByAuthorId(
+        string authorId,
+        [Service] AuthorRepository repository) {
+            Author author = repository.GetAuthorById(authorId);
+            return new Book(authorId, author);
+        }
+}

src/HotChocolate/Fusion/test/Shared/Authors/AuthorRepository.cs

@@ -0,0 +1,22 @@
+namespace HotChocolate.Fusion.Shared.Authors;
+
+public sealed class AuthorRepository
+{
+    private readonly Dictionary<string, Author> _authors;
+
+    public AuthorRepository()
+    {
+        _authors = new[]
+        {
+            new Author("1", "First author", "The first author")
+        }.ToDictionary(t => t.Id);
+    }
+
+     public IEnumerable<Author> GetAuthors(int limit)
+        => _authors.Values.OrderBy(t => t.Id).Take(limit);
+
+    public Author? GetAuthorById(string id)
+        => _authors.TryGetValue(id, out var author)
+            ? author
+            : null;
+}

src/HotChocolate/Fusion/test/Shared/Authors/Book.cs

@@ -0,0 +1,15 @@
+
+namespace HotChocolate.Fusion.Shared.Authors;
+
+public class Book
+{
+
+    public string AuthorId { get; set;}
+
+    public Author Author {get; set; }
+
+    public Book(string authorId, Author author) {
+        this.AuthorId = authorId;
+        this.Author = author;
+    }
+}

src/HotChocolate/Fusion/test/Shared/Books/Author.cs

@@ -0,0 +1,14 @@
+namespace HotChocolate.Fusion.Shared.Books;
+
+
+public class Author
+{
+    public string Id { get; set;}
+
+    public IEnumerable<Book> Books { get; set; }
+
+    public Author(string id, IEnumerable<Book> books) {
+        this.Id = id;
+        this.Books = books;
+    }
+}

src/HotChocolate/Fusion/test/Shared/Books/Book.cs

@@ -0,0 +1,17 @@
+namespace HotChocolate.Fusion.Shared.Books;
+
+public class Book
+{
+    public string Id { get; set;}
+
+    public string AuthorId { get; set;}
+
+    public string Title {get; set; }
+
+
+    public Book(string id, string authorId, string title) {
+        this.Id = id;
+        this.AuthorId = authorId;
+        this.Title = title;
+    }
+}

src/HotChocolate/Fusion/test/Shared/Books/BookQuery.cs

@@ -0,0 +1,18 @@
+namespace HotChocolate.Fusion.Shared.Books;
+
+[GraphQLName("Query")]
+public sealed class BookQuery
+{
+    public Book? BookById(
+        string id,
+        [Service] BookRepository repository)
+        => repository.GetBookById(id);
+
+    public IEnumerable<Book> Books(int limit, [Service] BookRepository repository) 
+        => repository.GetBooks(limit);
+
+    public Author authorById(
+        string id,
+        [Service] BookRepository repository) 
+        => new Author(id, repository.GetBooksByAuthorId(id));
+}

src/HotChocolate/Fusion/test/Shared/Books/BookRepository.cs

@@ -0,0 +1,25 @@
+namespace HotChocolate.Fusion.Shared.Books;
+
+public sealed class BookRepository
+{
+    private readonly Dictionary<string, Book> _books;
+
+    public BookRepository()
+    {
+        _books = new[]
+        {
+            new Book("1", "1", "The first book")
+        }.ToDictionary(t => t.Id);
+    }
+
+     public IEnumerable<Book> GetBooks(int limit)
+        => _books.Values.OrderBy(t => t.Id).Take(limit);
+
+    public Book? GetBookById(string id)
+        => _books.TryGetValue(id, out var book)
+            ? book
+            : null;
+
+     public IEnumerable<Book> GetBooksByAuthorId(string authorId)
+        => _books.Values.Where(b => b.AuthorId.Equals(authorId));
+}