Point fragments on a paged field to nodes

src/Linq2GraphQL.Client.AI/Schema/QueryValidator.cs

@@ -250,6 +250,16 @@ private SchemaType FragmentType(SchemaType parent, string typeName, string path)
                           parent.PossibleTypes.Contains(type.Name) ||
                           type.PossibleTypes.Contains(parent.Name) ||
                           type.PossibleTypes.Intersect(parent.PossibleTypes).Any();
+            if (!applies && shape.ConnectionOf(parent.Name) is { } connection &&
+                (connection.NodeType == type.Name || model.Type(connection.NodeType)?.PossibleTypes.Contains(type.Name) == true))
+            {
+                var pageField = connection.HasNodes ? "nodes" : "edges { node";
+                var close = connection.HasNodes ? "}" : "} }";
+                Error(path, $"This field is paged; put `... on {type.Name}` inside `{pageField} {{ ... on {type.Name} {{ ... }} {close}`, " +
+                            "for example `{ nodes { __typename ... on " + type.Name + " { ... } } pageInfo { hasNextPage endCursor } }`.");
+                return null;
+            }
+
             if (!applies)
             {
                 Error(path, $"A fragment on {type.Name} cannot apply to {parent.Name}.");

test/Linq2GraphQL.Agent.Sample/questions.json

@@ -6,5 +6,6 @@
   { "question": "Which customer has an order delivered to Garden Inc?", "expected": ["Universal Ltd"] },
   { "question": "What is the price of item 12345 on Universal Ltd's orders?", "expected": ["56.4"] },
   { "question": "What is the name of the spider, and how many legs does it have?", "expected": ["Imse", "8"] },
-  { "question": "Which animal has the most legs?", "expected": ["Imse"] }
+  { "question": "What is the name of the animal with the most legs?", "expected": ["Imse"] },
+  { "question": "What is the speed of each animal?", "expected": ["Kalle", "5", "Imse", "11"] }
 ]

test/Linq2GraphQL.Tests/QueryValidatorTests.cs

@@ -125,6 +125,15 @@ public void PagedField_SelectedDirectly_GetsTheFix()
             .ShouldContain("orders.orderId: This field is paged; select orderId inside `nodes { orderId }`");
     }
 
+    [Fact]
+    public void PagedField_FragmentOnTheNodeType_GetsTheFix()
+    {
+        var errors = ShouldFail("{ animals { ... on Spider { name } } }");
+
+        errors.ShouldContain("animals: This field is paged; put `... on Spider` inside `nodes { ... on Spider { ... } }`");
+        errors.ShouldNotContain("cannot apply");
+    }
+
     [Fact]
     public void LeafAndCompositeSelections_AreChecked()
     {