Add tests for subgraph being offline

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

@@ -18,6 +18,104 @@ public class ErrorTests(ITestOutputHelper output)
 {
     private readonly Func<ICompositionLog> _logFactory = () => new TestCompositionLog(output);
 
+    [Fact]
+    public async Task Resolve_Parallel_Accounts_Offline_FieldNullable()
+    {
+        // arrange
+        using var demoProject = await DemoProject.CreateAsync();
+
+        var fusionGraph = await new FusionGraphComposer(logFactory: _logFactory).ComposeAsync(
+            new[]
+            {
+                demoProject.Accounts.ToConfiguration(AccountsExtensionSdl),
+                demoProject.Reviews2.ToConfiguration(Reviews2ExtensionSdl),
+            },
+            new FusionFeatureCollection(FusionFeatures.NodeField));
+
+        var executor = await new ServiceCollection()
+            .AddSingleton<IHttpClientFactory>(
+                new ErrorFactory(demoProject.HttpClientFactory, demoProject.Accounts.Name))
+            .AddSingleton(demoProject.WebSocketConnectionFactory)
+            .AddFusionGatewayServer()
+            .ConfigureFromDocument(SchemaFormatter.FormatAsDocument(fusionGraph))
+            .BuildRequestExecutorAsync();
+
+        var request = Parse(
+            """
+            {
+              viewer {
+                user {
+                  name
+                }
+                latestReview {
+                  body
+                }
+              }
+            }
+            """);
+
+        // act
+        await using var result = await executor.ExecuteAsync(
+            QueryRequestBuilder
+                .New()
+                .SetQuery(request)
+                .Create());
+
+        // assert
+        var snapshot = new Snapshot();
+        CollectSnapshotData(snapshot, request, result, fusionGraph);
+        snapshot.MatchMarkdownSnapshot();
+    }
+
+    [Fact]
+    public async Task Resolve_Parallel_Accounts_Offline_FieldNonNull()
+    {
+        // arrange
+        using var demoProject = await DemoProject.CreateAsync();
+
+        var fusionGraph = await new FusionGraphComposer(logFactory: _logFactory).ComposeAsync(
+            new[]
+            {
+                demoProject.Accounts.ToConfiguration(AccountsExtensionSdl),
+                demoProject.Reviews2.ToConfiguration(Reviews2ExtensionSdl),
+            },
+            new FusionFeatureCollection(FusionFeatures.NodeField));
+
+        var executor = await new ServiceCollection()
+            .AddSingleton<IHttpClientFactory>(
+                new ErrorFactory(demoProject.HttpClientFactory, demoProject.Accounts.Name))
+            .AddSingleton(demoProject.WebSocketConnectionFactory)
+            .AddFusionGatewayServer()
+            .ConfigureFromDocument(SchemaFormatter.FormatAsDocument(fusionGraph))
+            .BuildRequestExecutorAsync();
+
+        var request = Parse(
+            """
+            {
+              viewer? {
+                user! {
+                  name
+                }
+                latestReview {
+                  body
+                }
+              }
+            }
+            """);
+
+        // act
+        await using var result = await executor.ExecuteAsync(
+            QueryRequestBuilder
+                .New()
+                .SetQuery(request)
+                .Create());
+
+        // assert
+        var snapshot = new Snapshot();
+        CollectSnapshotData(snapshot, request, result, fusionGraph);
+        snapshot.MatchMarkdownSnapshot();
+    }
+
     [Fact]
     public async Task TopLevelResolveSubgraphError()
     {

src/HotChocolate/Fusion/test/Core.Tests/__snapshots__/ErrorTests.Resolve_Parallel_Accounts_Offline_FieldNonNull.md

@@ -0,0 +1,241 @@
+# Resolve_Parallel_Accounts_Offline_FieldNonNull
+
+## User Request
+
+```graphql
+{
+  viewer? {
+    user! {
+      name
+    }
+    latestReview {
+      body
+    }
+  }
+}
+```
+
+## Result
+
+```json
+{
+  "errors": [
+    {
+      "message": "Internal Execution Error"
+    }
+  ],
+  "data": null
+}
+```
+
+## QueryPlan
+
+```json
+{
+  "document": "{ viewer? { user! { name } latestReview { body } } }",
+  "rootNode": {
+    "type": "Sequence",
+    "nodes": [
+      {
+        "type": "Parallel",
+        "nodes": [
+          {
+            "type": "Resolve",
+            "subgraph": "Accounts",
+            "document": "query fetch_viewer_1 { viewer { user! { name } } }",
+            "selectionSetId": 0
+          },
+          {
+            "type": "Resolve",
+            "subgraph": "Reviews2",
+            "document": "query fetch_viewer_2 { viewer? { latestReview { body } } }",
+            "selectionSetId": 0
+          }
+        ]
+      },
+      {
+        "type": "Compose",
+        "selectionSetIds": [
+          0
+        ]
+      }
+    ]
+  }
+}
+```
+
+## QueryPlan Hash
+
+```text
+B1F8BD87F08DD7941DBB6AF4852DA3AA3EB10097
+```
+
+## Fusion Graph
+
+```graphql
+schema
+  @fusion(version: 1)
+  @transport(subgraph: "Accounts", location: "http:\/\/localhost:5000\/graphql", kind: "HTTP")
+  @transport(subgraph: "Accounts", location: "ws:\/\/localhost:5000\/graphql", kind: "WebSocket")
+  @transport(subgraph: "Reviews2", location: "http:\/\/localhost:5000\/graphql", kind: "HTTP")
+  @transport(subgraph: "Reviews2", location: "ws:\/\/localhost:5000\/graphql", kind: "WebSocket")
+  @node(subgraph: "Accounts", types: [ "User" ])
+  @node(subgraph: "Reviews2", types: [ "User", "Review" ]) {
+  query: Query
+  mutation: Mutation
+  subscription: Subscription
+}
+
+type Query {
+  errorField: String
+    @resolver(subgraph: "Accounts", select: "{ errorField }")
+  "Fetches an object given its ID."
+  node("ID of the object." id: ID!): Node
+    @variable(subgraph: "Accounts", name: "id", argument: "id")
+    @resolver(subgraph: "Accounts", select: "{ node(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+    @variable(subgraph: "Reviews2", name: "id", argument: "id")
+    @resolver(subgraph: "Reviews2", select: "{ node(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+  "Lookup nodes by a list of IDs."
+  nodes("The list of node IDs." ids: [ID!]!): [Node]!
+    @variable(subgraph: "Accounts", name: "ids", argument: "ids")
+    @resolver(subgraph: "Accounts", select: "{ nodes(ids: $ids) }", arguments: [ { name: "ids", type: "[ID!]!" } ])
+    @variable(subgraph: "Reviews2", name: "ids", argument: "ids")
+    @resolver(subgraph: "Reviews2", select: "{ nodes(ids: $ids) }", arguments: [ { name: "ids", type: "[ID!]!" } ])
+  productById(id: ID!): Product
+    @variable(subgraph: "Reviews2", name: "id", argument: "id")
+    @resolver(subgraph: "Reviews2", select: "{ productById(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+  reviewById(id: ID!): Review
+    @variable(subgraph: "Reviews2", name: "id", argument: "id")
+    @resolver(subgraph: "Reviews2", select: "{ reviewById(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+  reviewOrAuthor: ReviewOrAuthor!
+    @resolver(subgraph: "Reviews2", select: "{ reviewOrAuthor }")
+  reviews: [Review!]!
+    @resolver(subgraph: "Reviews2", select: "{ reviews }")
+  userById(id: ID!): User
+    @variable(subgraph: "Accounts", name: "id", argument: "id")
+    @resolver(subgraph: "Accounts", select: "{ userById(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+    @variable(subgraph: "Reviews2", name: "id", argument: "id")
+    @resolver(subgraph: "Reviews2", select: "{ authorById(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
+  users: [User!]!
+    @resolver(subgraph: "Accounts", select: "{ users }")
+  usersById(ids: [ID!]!): [User!]!
+    @variable(subgraph: "Accounts", name: "ids", argument: "ids")
+    @resolver(subgraph: "Accounts", select: "{ usersById(ids: $ids) }", arguments: [ { name: "ids", type: "[ID!]!" } ])
+  viewer: Viewer!
+    @resolver(subgraph: "Accounts", select: "{ viewer }")
+    @resolver(subgraph: "Reviews2", select: "{ viewer }")
+}
+
+type Mutation {
+  addReview(input: AddReviewInput!): AddReviewPayload!
+    @variable(subgraph: "Reviews2", name: "input", argument: "input")
+    @resolver(subgraph: "Reviews2", select: "{ addReview(input: $input) }", arguments: [ { name: "input", type: "AddReviewInput!" } ])
+  addUser(input: AddUserInput!): AddUserPayload!
+    @variable(subgraph: "Accounts", name: "input", argument: "input")
+    @resolver(subgraph: "Accounts", select: "{ addUser(input: $input) }", arguments: [ { name: "input", type: "AddUserInput!" } ])
+}
+
+type Subscription {
+  onNewReview: Review!
+    @resolver(subgraph: "Reviews2", select: "{ onNewReview }", kind: "SUBSCRIBE")
+}
+
+type AddReviewPayload {
+  review: Review
+    @source(subgraph: "Reviews2")
+}
+
+type AddUserPayload {
+  user: User
+    @source(subgraph: "Accounts")
+}
+
+type Product
+  @variable(subgraph: "Reviews2", name: "Product_id", select: "id")
+  @resolver(subgraph: "Reviews2", select: "{ productById(id: $Product_id) }", arguments: [ { name: "Product_id", type: "ID!" } ]) {
+  id: ID!
+    @source(subgraph: "Reviews2")
+  reviews: [Review!]!
+    @source(subgraph: "Reviews2")
+}
+
+type Review implements Node
+  @variable(subgraph: "Reviews2", name: "Review_id", select: "id")
+  @resolver(subgraph: "Reviews2", select: "{ reviewById(id: $Review_id) }", arguments: [ { name: "Review_id", type: "ID!" } ])
+  @resolver(subgraph: "Reviews2", select: "{ nodes(ids: $Review_id) { ... on Review { ... Review } } }", arguments: [ { name: "Review_id", type: "[ID!]!" } ], kind: "BATCH") {
+  author: User!
+    @source(subgraph: "Reviews2")
+  body: String!
+    @source(subgraph: "Reviews2")
+  errorField: String
+    @source(subgraph: "Reviews2")
+  id: ID!
+    @source(subgraph: "Reviews2")
+  product: Product!
+    @source(subgraph: "Reviews2")
+}
+
+type SomeData {
+  accountValue: String!
+    @source(subgraph: "Accounts")
+  reviewsValue: String!
+    @source(subgraph: "Reviews2")
+}
+
+"The user who wrote the review."
+type User implements Node
+  @variable(subgraph: "Accounts", name: "User_id", select: "id")
+  @variable(subgraph: "Reviews2", name: "User_id", select: "id")
+  @resolver(subgraph: "Accounts", select: "{ userById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ])
+  @resolver(subgraph: "Accounts", select: "{ usersById(ids: $User_id) }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH")
+  @resolver(subgraph: "Reviews2", select: "{ authorById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ])
+  @resolver(subgraph: "Reviews2", select: "{ nodes(ids: $User_id) { ... on User { ... User } } }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH") {
+  birthdate: Date!
+    @source(subgraph: "Accounts")
+  errorField: String
+    @source(subgraph: "Accounts")
+  id: ID!
+    @source(subgraph: "Accounts")
+    @source(subgraph: "Reviews2")
+  name: String!
+    @source(subgraph: "Accounts")
+    @source(subgraph: "Reviews2")
+  reviews: [Review!]!
+    @source(subgraph: "Reviews2")
+  username: String!
+    @source(subgraph: "Accounts")
+}
+
+type Viewer {
+  data: SomeData!
+    @source(subgraph: "Accounts")
+    @source(subgraph: "Reviews2")
+  latestReview: Review
+    @source(subgraph: "Reviews2")
+  user: User
+    @source(subgraph: "Accounts")
+}
+
+"The node interface is implemented by entities that have a global unique identifier."
+interface Node {
+  id: ID!
+}
+
+union ReviewOrAuthor = User | Review
+
+input AddReviewInput {
+  authorId: Int!
+  body: String!
+  upc: Int!
+}
+
+input AddUserInput {
+  birthdate: Date!
+  name: String!
+  username: String!
+}
+
+"The `Date` scalar represents an ISO-8601 compliant date type."
+scalar Date
+```
+