do not overwrite own AbortSignal if an external AbortSignal is passed in

.changeset/quiet-balloons-wave.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Fix a situation where a passed-in `AbortSignal` would override internal unsubscription cancellation behaviour.

.size-limits.json

@@ -1,6 +1,6 @@
 {
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (CJS)": 43776,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production) (CJS)": 38564,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\"": 33542,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production)": 27587
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (CJS)": 43876,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production) (CJS)": 38663,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\"": 33603,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"@apollo/client\" (production)": 27660
 }

src/link/http/BaseHttpLink.ts

@@ -25,6 +25,7 @@ import {
 import { selectURI } from "./selectURI.js";
 
 const backupFetch = maybe(() => fetch);
+function noop() {}
 
 export declare namespace BaseHttpLink {
   /**
@@ -322,11 +323,34 @@ export class BaseHttpLink extends ApolloLink {
         );
       }
 
-      let controller: AbortController | undefined;
-      if (!options.signal && typeof AbortController !== "undefined") {
-        controller = new AbortController();
-        options.signal = controller.signal;
+      let controller: AbortController | undefined = new AbortController();
+      let cleanupController = () => {
+        controller = undefined;
+      };
+      if (options.signal) {
+        const externalSignal: AbortSignal = options.signal;
+        // in an ideal world we could use `AbortSignal.any` here, but
+        // React Native uses https://github.com/mysticatea/abort-controller as
+        // a polyfill for `AbortController`, and it does not support `AbortSignal.any`.
+
+        const listener = () => {
+          controller?.abort(externalSignal.reason);
+        };
+        externalSignal.addEventListener("abort", listener, { once: true });
+        cleanupController = () => {
+          controller?.signal.removeEventListener("abort", cleanupController);
+          controller = undefined;
+          // on cleanup, we need to stop listening to `options.signal` to avoid memory leaks
+          externalSignal.removeEventListener("abort", listener);
+          cleanupController = noop;
+        };
+        // react native also does not support the addEventListener `signal` option
+        // so we have to simulate that ourself
+        controller.signal.addEventListener("abort", cleanupController, {
+          once: true,
+        });
       }
+      options.signal = controller.signal;
 
       if (useGETForQueries && !isMutationOperation(operation.query)) {
         options.method = "GET";
@@ -365,11 +389,11 @@ export class BaseHttpLink extends ApolloLink {
             }
           })
           .then(() => {
-            controller = undefined;
+            cleanupController();
             observer.complete();
           })
           .catch((err) => {
-            controller = undefined;
+            cleanupController();
             observer.error(err);
           });
 

src/link/http/__tests__/HttpLink.ts

@@ -1159,52 +1159,79 @@ describe("HttpLink", () => {
         expect(abortControllers[0].signal.aborted).toBe(true);
       });
 
-      it("a passed-in signal will be forwarded to the `fetch` call and not be overwritten by an internally-created one", () => {
-        const fetch = jest.fn(async (_uri, _options) =>
-          Response.json({ data: { stub: { id: "foo" } } }, { status: 200 })
-        );
-        const externalAbortController = new AbortController();
+      it("a passed-in signal that is aborted will fail the observable with an `AbortError`", async () => {
+        try {
+          fetchMock.restore();
+          fetchMock.postOnce(
+            "data",
+            async () => '{ "data": { "stub": { "id": "foo" } } }',
+            { delay: 100 }
+          );
 
-        const link = createHttpLink({
-          uri: "data",
-          fetch,
-          fetchOptions: { signal: externalAbortController.signal },
-        });
+          const externalAbortController = new AbortController();
+          const abortControllers = trackGlobalAbortControllers();
 
-        const sub = execute(link, { query: sampleQuery }).subscribe(
-          failingObserver
-        );
-        sub.unsubscribe();
+          const link = createHttpLink({
+            uri: "/data",
+          });
 
-        expect(fetch.mock.calls.length).toBe(1);
-        expect(fetch.mock.calls[0][1]).toEqual(
-          expect.objectContaining({ signal: externalAbortController.signal })
-        );
+          const observable = execute(link, {
+            query: sampleQuery,
+            context: {
+              fetchOptions: { signal: externalAbortController.signal },
+            },
+          });
+
+          const internalAbortController = abortControllers[0];
+
+          const stream = new ObservableStream(observable);
+          const externalReason = new Error("External abort reason");
+
+          externalAbortController.abort(externalReason);
+
+          await expect(stream).toEmitError(
+            // this not being `externalReason` is a quirk of `fetch-mock`:
+            // https://github.com/wheresrhys/fetch-mock/blob/605ec0afa6a5ff35066b9e01a9bcd688f3c25ce0/packages/fetch-mock/src/Router.ts#L164-L167
+            new DOMException("The operation was aborted.", "AbortError")
+          );
+
+          expect(externalAbortController).not.toBe(internalAbortController);
+          expect(externalAbortController.signal.aborted).toBe(true);
+          expect(externalAbortController.signal.reason).toBe(externalReason);
+          expect(internalAbortController.signal.aborted).toBe(true);
+          expect(internalAbortController.signal.reason).toBe(externalReason);
+        } finally {
+          fetchMock.restore();
+        }
       });
 
-      it("a passed-in signal that is cancelled will fail the observable with an `AbortError`", async () => {
+      it("a passed-in signal will not fully overwrite the internally created one", () => {
         try {
+          const externalAbortController = new AbortController();
+          const abortControllers = trackGlobalAbortControllers();
+
           fetchMock.restore();
           fetchMock.postOnce(
             "data",
             async () => '{ "data": { "stub": { "id": "foo" } } }'
           );
 
-          const externalAbortController = new AbortController();
-
-          const link = createHttpLink({
+          const link = new HttpLink({
             uri: "/data",
-            fetchOptions: { signal: externalAbortController.signal },
           });
 
-          const error = await new Promise<Error>((resolve) => {
-            execute(link, { query: sampleQuery }).subscribe({
-              ...failingObserver,
-              error: resolve,
-            });
-            externalAbortController.abort();
-          });
-          expect(error.name).toBe("AbortError");
+          const sub = execute(link, {
+            query: sampleQuery,
+            context: {
+              fetchOptions: { signal: externalAbortController.signal },
+            },
+          }).subscribe(failingObserver);
+          const internalAbortController = abortControllers[0];
+
+          sub.unsubscribe();
+
+          expect(externalAbortController.signal.aborted).toBe(false);
+          expect(internalAbortController.signal.aborted).toBe(true);
         } finally {
           fetchMock.restore();
         }