When the root field is shared between subgraphs and one of them throws, the errors are swallowed (#950)

Co-authored-by: Tomas Kroupa <tomas.kroupa@applifting.cz>
Co-authored-by: Arda TANRIKULU <ardatanrikulu@gmail.com>

Author: 3 people

.changeset/fast-beds-pump.md

@@ -0,0 +1,10 @@
+---
+'@graphql-tools/delegate': patch
+'@graphql-tools/federation': patch
+'@graphql-mesh/fusion-runtime': patch
+'@graphql-hive/gateway': patch
+'@graphql-tools/stitch': patch
+'@graphql-mesh/transport-common': patch
+---
+
+Errors should not be swallowed when it is thrown from the shared root

.github/workflows/test.yml

@@ -17,6 +17,7 @@ env:
 jobs:
   unit:
     strategy:
+      fail-fast: false
       matrix:
         node-version:
           - 18
@@ -54,6 +55,7 @@ jobs:
 
   leaks:
     strategy:
+      fail-fast: false
       matrix:
         node-version:
           - 18

packages/delegate/package.json

@@ -39,7 +39,7 @@
   },
   "dependencies": {
     "@graphql-tools/batch-execute": "workspace:^",
-    "@graphql-tools/executor": "^1.3.10",
+    "@graphql-tools/executor": "^1.4.7",
     "@graphql-tools/schema": "^10.0.11",
     "@graphql-tools/utils": "^10.8.1",
     "@repeaterjs/repeater": "^3.0.6",

packages/federation/src/supergraph.ts

@@ -1052,6 +1052,7 @@ export function getStitchingOptionsFromSupergraphSdl(
     }
     let executor: Executor = buildHTTPExecutor({
       endpoint,
+      serviceName: subgraphName,
       ...httpExecutorOpts,
     });
     if (globalThis.process?.env?.['DEBUG']) {
@@ -1307,6 +1308,31 @@ export function getStitchingOptionsFromSupergraphSdl(
           }
           const jobs: Promise<void>[] = [];
           let hasPromise = false;
+          const fieldNames = new Set<string>();
+          currentAvailableSelectionSet?.selections.forEach((selection) => {
+            if (
+              selection.kind === Kind.FIELD &&
+              selection.name.value === info.fieldName
+            ) {
+              selection.selectionSet?.selections.forEach((selection) => {
+                if (selection.kind === Kind.FIELD) {
+                  fieldNames.add(selection.name.value);
+                }
+              });
+            }
+          });
+          currentUnavailableSelectionSet?.selections.forEach((selection) => {
+            if (
+              selection.kind === Kind.FIELD &&
+              selection.name.value === info.fieldName
+            ) {
+              selection.selectionSet?.selections.forEach((selection) => {
+                if (selection.kind === Kind.FIELD) {
+                  fieldNames.add(selection.name.value);
+                }
+              });
+            }
+          });
           const mainJob = delegateToSchema({
             schema: currentSubschema,
             operation:
@@ -1357,9 +1383,11 @@ export function getStitchingOptionsFromSupergraphSdl(
             return jobs[0];
           }
           if (hasPromise) {
-            return Promise.all(jobs).then((results) => mergeResults(results));
+            return Promise.all(jobs).then((results) =>
+              mergeResults(results, fieldNames),
+            );
           }
-          return mergeResults(jobs);
+          return mergeResults(jobs, fieldNames);
         };
       if (operationType === 'subscription') {
         return {
@@ -1573,14 +1601,50 @@ const specifiedTypeNames = [
   '_Entity',
 ];
 
-function makeExternalObject(data: any, errors: Error[]) {
+function makeExternalObject(
+  data: any,
+  errors: Error[],
+  fieldNames: Set<string>,
+) {
   if (!isExternalObject(data) && typeof data === 'object' && data != null) {
     data[UNPATHED_ERRORS_SYMBOL] = errors;
   }
+  if (errors.length) {
+    const errorsToPop = [...errors];
+    const fieldNamesToPop: string[] = [];
+    for (const fieldName of fieldNames) {
+      if (data?.[fieldName] == null) {
+        fieldNamesToPop.push(fieldName);
+      }
+    }
+    while (fieldNamesToPop.length && errorsToPop.length) {
+      const fieldName = fieldNamesToPop.pop();
+      if (!fieldName) {
+        break;
+      }
+      const error = errorsToPop.pop();
+      if (!error) {
+        break;
+      }
+      let errorToSet: Error | undefined;
+      if (fieldNamesToPop.length || !errorsToPop.length) {
+        errorToSet = error;
+      } else {
+        errorToSet = new AggregateError(
+          errorsToPop,
+          errorsToPop.map((error) => error.message).join(', \n'),
+        );
+      }
+      if (errorToSet) {
+        data ||= {};
+        data[fieldName] = errorToSet;
+      }
+    }
+  }
   return data;
 }
 
-function mergeResults(results: unknown[]) {
+function mergeResults(results: unknown[], fieldNames: Set<string>) {
   const errors: Error[] = [];
   const datas: unknown[] = [];
   for (const result of results) {
@@ -1594,9 +1658,13 @@ function mergeResults(results: unknown[]) {
   }
   if (datas.length) {
     if (datas.length === 1) {
-      return makeExternalObject(datas[0], errors);
+      return makeExternalObject(datas[0], errors, fieldNames);
     }
-    return makeExternalObject(mergeDeep(datas, undefined, true, true), errors);
+    return makeExternalObject(
+      mergeDeep(datas, undefined, true, true),
+      errors,
+      fieldNames,
+    );
   }
   if (errors.length) {
     if (errors.length === 1) {