Fix issue where a query may not stop polling after unmount when in Strict mode with cache-and-network fetch policy

.changeset/smooth-spoons-cough.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Fix an issue where a polled query created in React strict mode may not stop polling after the component unmounts while using the `cache-and-network` fetch policy.

.size-limits.json

@@ -1,4 +1,4 @@
 {
-  "dist/apollo-client.min.cjs": 39540,
-  "import { ApolloClient, InMemoryCache, HttpLink } from \"dist/index.js\" (production)": 32826
+  "dist/apollo-client.min.cjs": 39544,
+  "import { ApolloClient, InMemoryCache, HttpLink } from \"dist/index.js\" (production)": 32831
 }

src/core/ObservableQuery.ts

@@ -781,7 +781,7 @@ Did you mean to call refetch(variables) instead of refetch({ variables })?`,
       options: { pollInterval },
     } = this;
 
-    if (!pollInterval) {
+    if (!pollInterval || !this.hasObservers()) {
       if (pollingInfo) {
         clearTimeout(pollingInfo.timeout);
         delete this.pollingInfo;

src/react/hooks/__tests__/useQuery.test.tsx

@@ -22,6 +22,7 @@ import {
   MockSubscriptionLink,
   mockSingleLink,
   tick,
+  wait,
 } from "../../../testing";
 import { QueryResult } from "../../types/types";
 import { useQuery } from "../useQuery";
@@ -1887,6 +1888,86 @@ describe("useQuery Hook", () => {
       requestSpy.mockRestore();
     });
 
+    // https://github.com/apollographql/apollo-client/issues/9431
+    // https://github.com/apollographql/apollo-client/issues/11750
+    it("stops polling when component unmounts with cache-and-network fetch policy", async () => {
+      const query: TypedDocumentNode<{ hello: string }> = gql`
+        query {
+          hello
+        }
+      `;
+
+      const mocks = [
+        {
+          request: { query },
+          result: { data: { hello: "world 1" } },
+        },
+        {
+          request: { query },
+          result: { data: { hello: "world 2" } },
+        },
+        {
+          request: { query },
+          result: { data: { hello: "world 3" } },
+        },
+      ];
+
+      const cache = new InMemoryCache();
+
+      const link = new MockLink(mocks);
+      const requestSpy = jest.spyOn(link, "request");
+      const onErrorFn = jest.fn();
+      link.setOnError(onErrorFn);
+
+      const ProfiledHook = profileHook(() =>
+        useQuery(query, { pollInterval: 10, fetchPolicy: "cache-and-network" })
+      );
+
+      const client = new ApolloClient({
+        queryDeduplication: false,
+        link,
+        cache,
+      });
+
+      const { unmount } = render(<ProfiledHook />, {
+        wrapper: ({ children }: any) => (
+          <ApolloProvider client={client}>{children}</ApolloProvider>
+        ),
+      });
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(true);
+        expect(snapshot.data).toBeUndefined();
+      }
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(false);
+        expect(snapshot.data).toEqual({ hello: "world 1" });
+        expect(requestSpy).toHaveBeenCalledTimes(1);
+      }
+
+      await wait(10);
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(false);
+        expect(snapshot.data).toEqual({ hello: "world 2" });
+        expect(requestSpy).toHaveBeenCalledTimes(2);
+      }
+
+      unmount();
+
+      await expect(ProfiledHook).not.toRerender({ timeout: 50 });
+
+      expect(requestSpy).toHaveBeenCalledTimes(2);
+      expect(onErrorFn).toHaveBeenCalledTimes(0);
+    });
+
     it("should stop polling when component is unmounted in Strict Mode", async () => {
       const query = gql`
         {
@@ -1960,6 +2041,84 @@ describe("useQuery Hook", () => {
       requestSpy.mockRestore();
     });
 
+    // https://github.com/apollographql/apollo-client/issues/9431
+    // https://github.com/apollographql/apollo-client/issues/11750
+    it("stops polling when component unmounts in strict mode with cache-and-network fetch policy", async () => {
+      const query: TypedDocumentNode<{ hello: string }> = gql`
+        query {
+          hello
+        }
+      `;
+
+      const mocks = [
+        {
+          request: { query },
+          result: { data: { hello: "world 1" } },
+        },
+        {
+          request: { query },
+          result: { data: { hello: "world 2" } },
+        },
+        {
+          request: { query },
+          result: { data: { hello: "world 3" } },
+        },
+      ];
+
+      const cache = new InMemoryCache();
+
+      const link = new MockLink(mocks);
+      const requestSpy = jest.spyOn(link, "request");
+      const onErrorFn = jest.fn();
+      link.setOnError(onErrorFn);
+
+      const ProfiledHook = profileHook(() =>
+        useQuery(query, { pollInterval: 10, fetchPolicy: "cache-and-network" })
+      );
+
+      const client = new ApolloClient({ link, cache });
+
+      const { unmount } = render(<ProfiledHook />, {
+        wrapper: ({ children }: any) => (
+          <React.StrictMode>
+            <ApolloProvider client={client}>{children}</ApolloProvider>
+          </React.StrictMode>
+        ),
+      });
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(true);
+        expect(snapshot.data).toBeUndefined();
+      }
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(false);
+        expect(snapshot.data).toEqual({ hello: "world 1" });
+        expect(requestSpy).toHaveBeenCalledTimes(1);
+      }
+
+      await wait(10);
+
+      {
+        const snapshot = await ProfiledHook.takeSnapshot();
+
+        expect(snapshot.loading).toBe(false);
+        expect(snapshot.data).toEqual({ hello: "world 2" });
+        expect(requestSpy).toHaveBeenCalledTimes(2);
+      }
+
+      unmount();
+
+      await expect(ProfiledHook).not.toRerender({ timeout: 50 });
+
+      expect(requestSpy).toHaveBeenCalledTimes(2);
+      expect(onErrorFn).toHaveBeenCalledTimes(0);
+    });
+
     it("should start and stop polling in Strict Mode", async () => {
       const query = gql`
         {