Clean up subscriptions using requestIdleCallback instead of setTimeout

.changeset/brown-cats-report.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Clean up subscriptions using requestIdleCallback instead of setTimeout

src/core/ObservableQuery.ts

@@ -17,6 +17,7 @@ import {
   fixObservableSubclass,
   getQueryDefinition,
 } from "../utilities/index.js";
+import { requestIdleCallback } from "../utilities/common/requestIdleCallback.js";
 import type { ApolloError } from "../errors/index.js";
 import type { QueryManager } from "./QueryManager.js";
 import type {
@@ -204,7 +205,7 @@ export class ObservableQuery<
           //
           // We do this in order to prevent observers piling up within
           // the QueryManager. Notice that we only fully unsubscribe
-          // from the subscription in a setTimeout(..., 0)  call. This call can
+          // from the subscription in an idle callback. This callback can
           // actually be handled by the browser at a much later time. If queries
           // are fired in the meantime, observers that should have been removed
           // from the QueryManager will continue to fire, causing an unnecessary
@@ -214,9 +215,9 @@ export class ObservableQuery<
             this.queryManager.removeQuery(this.queryId);
           }
 
-          setTimeout(() => {
+          requestIdleCallback(() => {
             subscription.unsubscribe();
-          }, 0);
+          });
         },
         error: reject,
       };

src/utilities/common/__tests__/requestIdleCallback.ts

@@ -0,0 +1,39 @@
+import { requestIdleCallback } from "../requestIdleCallback";
+
+describe("requestIdleCallback", () => {
+  const originalRequestIdleCallback = window.requestIdleCallback;
+
+  afterAll(() => {
+    Object.defineProperty(window, "requestIdleCallback", {
+      value: originalRequestIdleCallback,
+    });
+  });
+
+  it("should use the window method when possible", () => {
+    Object.defineProperty(window, "requestIdleCallback", {
+      value: jest.fn((callback) => callback()),
+      configurable: true,
+    });
+
+    const task = jest.fn();
+    requestIdleCallback(task);
+    expect(task).toHaveBeenCalled();
+  });
+
+  it("should fall back to setTimeout when the window method is not available", () => {
+    // @ts-expect-error
+    delete window.requestIdleCallback;
+
+    jest.useFakeTimers();
+
+    const task = jest.fn();
+    requestIdleCallback(task);
+
+    expect(task).not.toHaveBeenCalled();
+
+    jest.runAllTimers();
+    expect(task).toHaveBeenCalled();
+
+    jest.useRealTimers();
+  });
+});

src/utilities/common/requestIdleCallback.ts

@@ -0,0 +1,15 @@
+/**
+ * Light polyfill for requestIdleCallback when used in non-browser environments.
+ */
+export function requestIdleCallback(
+  callback: () => void,
+  options?: IdleRequestOptions
+) {
+  if (
+    !Object.prototype.hasOwnProperty.call(window, "requestIdleCallback") ||
+    typeof window.requestIdleCallback === "undefined"
+  ) {
+    return setTimeout(callback, options?.timeout ?? 0);
+  }
+  return window.requestIdleCallback(callback, options);
+}