Composite computed fields

.changeset/little-hairs-kiss.md

@@ -0,0 +1,7 @@
+---
+'@graphql-tools/stitch': minor
+'@graphql-tools/stitching-directives': patch
+---
+
+Adding the ability to return non-scalar types from computed fields. Computed fields can now return
+object types (local or stitched), interfaces, unions, or enums.

packages/federation/test/__snapshots__/supergraphs.test.ts.snap

@@ -199,11 +199,6 @@ type Query {
   review(id: Int!): Review
 }
 
-type DeliveryEstimates {
-  estimatedDelivery: String
-  fastestDelivery: String
-}
-
 type Product implements ProductItf & SkuItf {
   id: ID! @tag(name: "hi-from-products")
   delivery(zip: String): DeliveryEstimates
@@ -246,6 +241,11 @@ enum ShippingClass {
   OVERNIGHT
 }
 
+type DeliveryEstimates {
+  estimatedDelivery: String
+  fastestDelivery: String
+}
+
 type Panda {
   name: ID!
   favoriteFood: String @tag(name: "nom-nom-nom")

packages/stitch/src/createDelegationPlanBuilder.ts

@@ -68,7 +68,29 @@ function calculateDelegationStage(
 
   const delegationMap: Map<Subschema, SelectionSetNode> = new Map();
   for (const fieldNode of fieldNodes) {
-    if (fieldNode.name.value === '__typename') {
+    const fieldName = fieldNode.name.value;
+    if (fieldName === '__typename') {
+      continue;
+    }
+
+    // check dependencies for computed fields are available in the source schemas
+    const sourcesWithUnsatisfiedDependencies = sourceSubschemas.filter(
+      s =>
+        fieldSelectionSets.get(s) != null &&
+        fieldSelectionSets.get(s)![fieldName] != null &&
+        !subschemaTypesContainSelectionSet(
+          mergedTypeInfo,
+          sourceSubschemas,
+          fieldSelectionSets.get(s)![fieldName],
+        ),
+    );
+    if (sourcesWithUnsatisfiedDependencies.length === sourceSubschemas.length) {
+      unproxiableFieldNodes.push(fieldNode);
+      for (const source of sourcesWithUnsatisfiedDependencies) {
+        if (!nonProxiableSubschemas.includes(source)) {
+          nonProxiableSubschemas.push(source);
+        }
+      }
       continue;
     }
 

packages/stitch/src/getFieldsNotInSubschema.ts

@@ -27,6 +27,7 @@ export function getFieldsNotInSubschema(
   const fieldsNotInSchema = new Set<FieldNode>();
   for (const [, subFieldNodes] of subFieldNodesByResponseKey) {
     const fieldName = subFieldNodes[0].name.value;
+
     if (!fields[fieldName]) {
       for (const subFieldNode of subFieldNodes) {
         fieldsNotInSchema.add(subFieldNode);
@@ -35,7 +36,12 @@ export function getFieldsNotInSubschema(
     const fieldNodesForField = fieldNodesByField?.[gatewayType.name]?.[fieldName];
     if (fieldNodesForField) {
       for (const fieldNode of fieldNodesForField) {
-        if (!fields[fieldNode.name.value]) {
+        if (fieldNode.name.value !== '__typename' && !fields[fieldNode.name.value]) {
+          // consider node that depends on something not in the schema as not in the schema
+          for (const subFieldNode of subFieldNodes) {
+            fieldsNotInSchema.add(subFieldNode);
+          }
+
           fieldsNotInSchema.add(fieldNode);
         }
       }