cancel execution despite hanging async resolvers

src/execution/Canceller.ts

@@ -0,0 +1,48 @@
+import { promiseWithResolvers } from '../jsutils/promiseWithResolvers.js';
+
+/**
+ * A Canceller object that can be used to cancel multiple promises
+ * using a single AbortSignal.
+ *
+ * @internal
+ */
+export class Canceller {
+  abortSignal: AbortSignal;
+  abort: () => void;
+
+  private _aborts: Set<() => void>;
+
+  constructor(abortSignal: AbortSignal) {
+    this.abortSignal = abortSignal;
+    this._aborts = new Set<() => void>();
+    this.abort = () => {
+      for (const abort of this._aborts) {
+        abort();
+      }
+    };
+
+    abortSignal.addEventListener('abort', this.abort);
+  }
+
+  unsubscribe(): void {
+    this.abortSignal.removeEventListener('abort', this.abort);
+  }
+
+  withCancellation<T>(originalPromise: Promise<T>): Promise<T> {
+    const { promise, resolve, reject } = promiseWithResolvers<T>();
+    const abort = () => reject(this.abortSignal.reason);
+    this._aborts.add(abort);
+    originalPromise.then(
+      (resolved) => {
+        this._aborts.delete(abort);
+        resolve(resolved);
+      },
+      (error: unknown) => {
+        this._aborts.delete(abort);
+        reject(error);
+      },
+    );
+
+    return promise;
+  }
+}

src/execution/IncrementalPublisher.ts

@@ -4,6 +4,7 @@ import { pathToArray } from '../jsutils/Path.js';
 
 import type { GraphQLError } from '../error/GraphQLError.js';
 
+import type { Canceller } from './Canceller.js';
 import { IncrementalGraph } from './IncrementalGraph.js';
 import type {
   CancellableStreamRecord,
@@ -43,6 +44,7 @@ export function buildIncrementalResponse(
 }
 
 interface IncrementalPublisherContext {
+  canceller: Canceller | undefined;
   cancellableStreams: Set<CancellableStreamRecord> | undefined;
 }
 
@@ -125,6 +127,7 @@ class IncrementalPublisher {
       IteratorResult<SubsequentIncrementalExecutionResult, void>
     > => {
       if (isDone) {
+        this._context.canceller?.unsubscribe();
         await this._returnAsyncIteratorsIgnoringErrors();
         return { value: undefined, done: true };
       }
@@ -171,6 +174,9 @@ class IncrementalPublisher {
         batch = await this._incrementalGraph.nextCompletedBatch();
       } while (batch !== undefined);
 
+      // TODO: add test for this case
+      /* c8 ignore next */
+      this._context.canceller?.unsubscribe();
       await this._returnAsyncIteratorsIgnoringErrors();
       return { value: undefined, done: true };
     };

src/execution/__tests__/abort-signal-test.ts

@@ -9,7 +9,11 @@ import { parse } from '../../language/parser.js';
 
 import { buildSchema } from '../../utilities/buildASTSchema.js';
 
-import { execute, experimentalExecuteIncrementally } from '../execute.js';
+import {
+  execute,
+  experimentalExecuteIncrementally,
+  subscribe,
+} from '../execute.js';
 import type {
   InitialIncrementalExecutionResult,
   SubsequentIncrementalExecutionResult,
@@ -52,12 +56,17 @@ const schema = buildSchema(`
 
   type Query {
     todo: Todo
+    nonNullableTodo: Todo!
   }
 
   type Mutation {
     foo: String
     bar: String
   }
+
+  type Subscription {
+    foo: String
+  }
 `);
 
 describe('Execute: Cancellation', () => {
@@ -300,6 +309,97 @@ describe('Execute: Cancellation', () => {
     });
   });
 
+  it('should stop the execution when aborted despite a hanging resolver', async () => {
+    const abortController = new AbortController();
+    const document = parse(`
+      query {
+        todo {
+          id
+          author {
+            id
+          }
+        }
+      }
+    `);
+
+    const resultPromise = execute({
+      document,
+      schema,
+      abortSignal: abortController.signal,
+      rootValue: {
+        todo: () =>
+          new Promise(() => {
+            /* will never resolve */
+          }),
+      },
+    });
+
+    abortController.abort();
+
+    const result = await resultPromise;
+
+    expect(result.errors?.[0].originalError?.name).to.equal('AbortError');
+
+    expectJSON(result).toDeepEqual({
+      data: {
+        todo: null,
+      },
+      errors: [
+        {
+          message: 'This operation was aborted',
+          path: ['todo'],
+          locations: [{ line: 3, column: 9 }],
+        },
+      ],
+    });
+  });
+
+  it('should stop the execution when aborted with proper null bubbling', async () => {
+    const abortController = new AbortController();
+    const document = parse(`
+      query {
+        nonNullableTodo {
+          id
+          author {
+            id
+          }
+        }
+      }
+    `);
+
+    const resultPromise = execute({
+      document,
+      schema,
+      abortSignal: abortController.signal,
+      rootValue: {
+        nonNullableTodo: async () =>
+          Promise.resolve({
+            id: '1',
+            text: 'Hello, World!',
+            /* c8 ignore next */
+            author: () => expect.fail('Should not be called'),
+          }),
+      },
+    });
+
+    abortController.abort();
+
+    const result = await resultPromise;
+
+    expect(result.errors?.[0].originalError?.name).to.equal('AbortError');
+
+    expectJSON(result).toDeepEqual({
+      data: null,
+      errors: [
+        {
+          message: 'This operation was aborted',
+          path: ['nonNullableTodo'],
+          locations: [{ line: 3, column: 9 }],
+        },
+      ],
+    });
+  });
+
   it('should stop deferred execution when aborted', async () => {
     const abortController = new AbortController();
     const document = parse(`
@@ -353,14 +453,12 @@ describe('Execute: Cancellation', () => {
     const abortController = new AbortController();
     const document = parse(`
       query {
-        todo {
-          id
-          ... on Todo @defer {
+        ... on Query @defer {
+          todo {
+            id
             text
             author {
-              ... on Author @defer {
-                id
-              }
+              id
             }
           }
         }
@@ -382,41 +480,27 @@ describe('Execute: Cancellation', () => {
       abortController.signal,
     );
 
-    await resolveOnNextTick();
-    await resolveOnNextTick();
-    await resolveOnNextTick();
-
     abortController.abort();
 
     const result = await resultPromise;
 
     expectJSON(result).toDeepEqual([
       {
-        data: {
-          todo: {
-            id: '1',
-          },
-        },
-        pending: [{ id: '0', path: ['todo'] }],
+        data: {},
+        pending: [{ id: '0', path: [] }],
         hasNext: true,
       },
       {
         incremental: [
           {
             data: {
-              text: 'hello world',
-              author: null,
+              todo: null,
             },
             errors: [
               {
-                locations: [
-                  {
-                    column: 13,
-                    line: 7,
-                  },
-                ],
                 message: 'This operation was aborted',
-                path: ['todo', 'author'],
+                path: ['todo'],
+                locations: [{ line: 4, column: 11 }],
               },
             ],
             id: '0',
@@ -448,6 +532,10 @@ describe('Execute: Cancellation', () => {
       },
     });
 
+    await resolveOnNextTick();
+    await resolveOnNextTick();
+    await resolveOnNextTick();
+
     abortController.abort();
 
     const result = await resultPromise;
@@ -498,4 +586,39 @@ describe('Execute: Cancellation', () => {
       ],
     });
   });
+
+  it('should stop the execution when aborted during subscription', async () => {
+    const abortController = new AbortController();
+    const document = parse(`
+      subscription {
+        foo
+      }
+    `);
+
+    const resultPromise = subscribe({
+      document,
+      schema,
+      abortSignal: abortController.signal,
+      rootValue: {
+        foo: async () =>
+          new Promise(() => {
+            /* will never resolve */
+          }),
+      },
+    });
+
+    abortController.abort();
+
+    const result = await resultPromise;
+
+    expectJSON(result).toDeepEqual({
+      errors: [
+        {
+          message: 'This operation was aborted',
+          path: ['foo'],
+          locations: [{ line: 3, column: 9 }],
+        },
+      ],
+    });
+  });
 });