Make useRenderGuard more resilient to changes in React internals.

.changeset/early-pens-kick.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Make `useRenderGuard` more resilient to changes in React internals.

.size-limits.json

@@ -1,4 +1,4 @@
 {
-  "dist/apollo-client.min.cjs": 39245,
+  "dist/apollo-client.min.cjs": 39247,
   "import { ApolloClient, InMemoryCache, HttpLink } from \"dist/index.js\" (production)": 32630
 }

src/react/hooks/internal/__tests__/useRenderGuard.test.tsx

@@ -0,0 +1,76 @@
+/* eslint-disable testing-library/render-result-naming-convention */
+import React, { useEffect } from "react";
+import { useRenderGuard } from "../useRenderGuard";
+import { render, waitFor } from "@testing-library/react";
+import { withCleanup } from "../../../../testing/internal";
+
+const UNDEF = {};
+
+it("returns a function that returns `true` if called during render", () => {
+  let result: boolean | typeof UNDEF = UNDEF;
+  function TestComponent() {
+    const calledDuringRender = useRenderGuard();
+    result = calledDuringRender();
+    return <>Test</>;
+  }
+  render(<TestComponent />);
+  expect(result).toBe(true);
+});
+
+it("returns a function that returns `false` if called after render", async () => {
+  let result: boolean | typeof UNDEF = UNDEF;
+  function TestComponent() {
+    const calledDuringRender = useRenderGuard();
+    useEffect(() => {
+      result = calledDuringRender();
+    });
+    return <>Test</>;
+  }
+  render(<TestComponent />);
+  await waitFor(() => {
+    expect(result).not.toBe(UNDEF);
+  });
+  expect(result).toBe(false);
+});
+
+function breakReactInternalsTemporarily() {
+  const R = React as unknown as {
+    __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED: any;
+  };
+  const orig = R.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED;
+
+  R.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED = {};
+  return withCleanup({}, () => {
+    R.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED = orig;
+  });
+}
+
+it("results in false negatives if React internals change", () => {
+  let result: boolean | typeof UNDEF = UNDEF;
+  function TestComponent() {
+    using _ = breakReactInternalsTemporarily();
+    const calledDuringRender = useRenderGuard();
+    result = calledDuringRender();
+    return <>Test</>;
+  }
+  render(<TestComponent />);
+  expect(result).toBe(false);
+});
+
+it("does not result in false positives if React internals change", async () => {
+  let result: boolean | typeof UNDEF = UNDEF;
+  function TestComponent() {
+    using _ = breakReactInternalsTemporarily();
+    const calledDuringRender = useRenderGuard();
+    useEffect(() => {
+      using _ = breakReactInternalsTemporarily();
+      result = calledDuringRender();
+    });
+    return <>Test</>;
+  }
+  render(<TestComponent />);
+  await waitFor(() => {
+    expect(result).not.toBe(UNDEF);
+  });
+  expect(result).toBe(false);
+});

src/react/hooks/internal/useRenderGuard.ts

@@ -16,7 +16,7 @@ export function useRenderGuard() {
 
   return React.useCallback(() => {
     return (
-      RenderDispatcher !== null && RenderDispatcher === getRenderDispatcher()
+      RenderDispatcher != null && RenderDispatcher === getRenderDispatcher()
     );
   }, []);
 }