cloudflare__vinext/tests/prefetch-cache.test.ts

/**
 * Prefetch cache eviction tests.
 *
 * Verifies that storePrefetchResponse() sweeps expired entries before
 * falling back to FIFO eviction, preventing expired entries from wasting
 * cache slots on link-heavy pages.
 *
 * The navigation module computes `isServer = typeof window === "undefined"`
 * at load time, so we must set globalThis.window BEFORE importing it via
 * vi.resetModules() + dynamic import().
 */
import { describe, it, expect, beforeEach, afterEach, vi } from "vite-plus/test";
import { AppElementsWire } from "../packages/vinext/src/server/app-elements.js";

type Navigation = typeof import("../packages/vinext/src/shims/navigation.js");
let storePrefetchResponse: Navigation["storePrefetchResponse"];
let consumePrefetchResponse: Navigation["consumePrefetchResponse"];
let getPrefetchCache: Navigation["getPrefetchCache"];
let getPrefetchedUrls: Navigation["getPrefetchedUrls"];
let getCurrentInterceptionContext: Navigation["getCurrentInterceptionContext"];
let MAX_PREFETCH_CACHE_SIZE: Navigation["MAX_PREFETCH_CACHE_SIZE"];
let PREFETCH_CACHE_TTL: Navigation["PREFETCH_CACHE_TTL"];
let snapshotRscResponse: Navigation["snapshotRscResponse"];
let restoreRscResponse: Navigation["restoreRscResponse"];
let useRouter: Navigation["useRouter"];

beforeEach(async () => {
  // Set window BEFORE importing so isServer evaluates to false
  (globalThis as any).window = {
    __VINEXT_RSC_PREFETCH_CACHE__: new Map(),
    __VINEXT_RSC_PREFETCHED_URLS__: new Set(),
    location: {
      origin: "http://localhost",
      pathname: "/",
      search: "",
      hash: "",
      href: "http://localhost/",
    },
    addEventListener: () => {},
    history: { pushState: () => {}, replaceState: () => {}, state: null },
    dispatchEvent: () => {},
  };
  vi.resetModules();
  const nav = await import("../packages/vinext/src/shims/navigation.js");
  storePrefetchResponse = nav.storePrefetchResponse;
  consumePrefetchResponse = nav.consumePrefetchResponse;
  getPrefetchCache = nav.getPrefetchCache;
  getPrefetchedUrls = nav.getPrefetchedUrls;
  getCurrentInterceptionContext = nav.getCurrentInterceptionContext;
  MAX_PREFETCH_CACHE_SIZE = nav.MAX_PREFETCH_CACHE_SIZE;
  PREFETCH_CACHE_TTL = nav.PREFETCH_CACHE_TTL;
  snapshotRscResponse = nav.snapshotRscResponse;
  restoreRscResponse = nav.restoreRscResponse;
  useRouter = nav.useRouter;
});

afterEach(() => {
  vi.restoreAllMocks();
  delete (globalThis as any).window;
  delete (globalThis as any).fetch;
});

/** Helper: fill cache with `count` entries at a given timestamp. */
function fillCache(count: number, timestamp: number, keyPrefix = "/page-"): void {
  const cache = getPrefetchCache();
  const prefetched = getPrefetchedUrls();
  for (let i = 0; i < count; i++) {
    const key = `${keyPrefix}${i}.rsc`;
    const body = `body-${i}`;
    const buffer = new TextEncoder().encode(body).buffer;
    cache.set(key, {
      snapshot: {
        buffer,
        contentType: "text/x-component",
        paramsHeader: null,
        url: key,
      },
      outcome: "cache-seeded",
      timestamp,
    });
    prefetched.add(key);
  }
}

async function waitForPrefetchSetup(isReady: () => boolean = () => true): Promise<void> {
  const deadline = Date.now() + 1_000;

  do {
    await Promise.resolve();
    if (isReady()) return;
    await new Promise((resolve) => setTimeout(resolve, 0));
  } while (Date.now() < deadline);
}

describe("prefetch cache eviction", () => {
  it("router.prefetch ignores external absolute URLs", async () => {
    const fetch = vi.fn();
    (globalThis as any).fetch = fetch;

    useRouter().prefetch("https://external.example/dashboard");
    await waitForPrefetchSetup();

    expect(fetch).not.toHaveBeenCalled();
    expect(getPrefetchedUrls().size).toBe(0);
  });

  it("router.prefetch normalizes same-origin absolute URLs before caching", async () => {
    let fetchedUrl: unknown;
    const fetch = vi.fn(async (input: RequestInfo | URL) => {
      fetchedUrl = input;
      return new Response("flight", { headers: { "content-type": "text/x-component" } });
    });
    (globalThis as any).fetch = fetch;

    useRouter().prefetch("http://localhost/dashboard?tab=1");
    await waitForPrefetchSetup(() => fetch.mock.calls.length > 0);

    expect(fetch).toHaveBeenCalledTimes(1);
    expect(fetchedUrl).toMatch(/^\/dashboard\.rsc\?tab=1&_rsc(?:=.+)?$/);
    expect(getPrefetchedUrls().has(AppElementsWire.encodeCacheKey(String(fetchedUrl), "/"))).toBe(
      true,
    );
  });

  it("reuses a prefetched response only when mounted-slot context matches", () => {
    const cache = getPrefetchCache();
    const prefetched = getPrefetchedUrls();
    const rscUrl = "/dashboard.rsc";
    const snapshot = {
      buffer: new TextEncoder().encode("flight").buffer,
      contentType: "text/x-component",
      mountedSlotsHeader: "slot:auth:/",
      paramsHeader: null,
      url: rscUrl,
    };

    cache.set(rscUrl, { outcome: "cache-seeded", snapshot, timestamp: Date.now() });
    prefetched.add(rscUrl);

    expect(consumePrefetchResponse(rscUrl, null, "slot:auth:/")).toEqual(snapshot);
    expect(cache.has(rscUrl)).toBe(false);
    expect(prefetched.has(rscUrl)).toBe(false);
  });

  it("rejects a prefetched response when mounted-slot context differs", () => {
    const cache = getPrefetchCache();
    const prefetched = getPrefetchedUrls();
    const rscUrl = "/dashboard.rsc";

    cache.set(rscUrl, {
      outcome: "cache-seeded",
      snapshot: {
        buffer: new TextEncoder().encode("flight").buffer,
        contentType: "text/x-component",
        mountedSlotsHeader: "slot:auth:/",
        paramsHeader: null,
        url: rscUrl,
      },
      timestamp: Date.now(),
    });
    prefetched.add(rscUrl);

    expect(consumePrefetchResponse(rscUrl, null, "slot:nav:/")).toBeNull();
    expect(cache.has(rscUrl)).toBe(false);
    expect(prefetched.has(rscUrl)).toBe(false);
  });

  it("derives the interception context from the current pathname", () => {
    (globalThis as any).window.location.pathname = "/feed";

    expect(getCurrentInterceptionContext()).toBe("/feed");
  });

  it("allows separate interception-context entries for the same RSC URL", () => {
    storePrefetchResponse("/photos/42.rsc", new Response("feed"), "/feed");
    storePrefetchResponse("/photos/42.rsc", new Response("gallery"), "/gallery");

    const feedKey = AppElementsWire.encodeCacheKey("/photos/42.rsc", "/feed");
    const galleryKey = AppElementsWire.encodeCacheKey("/photos/42.rsc", "/gallery");
    expect(feedKey).not.toBe(galleryKey);
    expect(getPrefetchCache().has(feedKey)).toBe(true);
    expect(getPrefetchCache().has(galleryKey)).toBe(true);
  });

  it("preserves X-Vinext-Params when replaying cached RSC responses", async () => {
    const response = new Response("flight", {
      headers: {
        "content-type": "text/x-component; charset=utf-8",
        "x-vinext-params": encodeURIComponent('{"id":"2"}'),
      },
    });

    const snapshot = await snapshotRscResponse(response);
    const restored = restoreRscResponse(snapshot);

    expect(restored.headers.get("content-type")).toBe("text/x-component; charset=utf-8");
    expect(restored.headers.get("x-vinext-params")).toBe(encodeURIComponent('{"id":"2"}'));
    await expect(restored.text()).resolves.toBe("flight");
  });

  it("settles router.prefetch as a consumable cache-seeded response without visible navigation", async () => {
    let resolveResponse!: (response: Response) => void;
    const fetchPromise = new Promise<Response>((resolve) => {
      resolveResponse = resolve;
    });
    let fetchedUrl: RequestInfo | URL | undefined;
    const fetch = vi.fn((input: RequestInfo | URL) => {
      fetchedUrl = input;
      return fetchPromise;
    });
    const navigate = vi.fn();
    (globalThis as any).fetch = fetch;
    (globalThis as any).window.__VINEXT_RSC_NAVIGATE__ = navigate;

    useRouter().prefetch("/dashboard");
    await waitForPrefetchSetup(() => fetch.mock.calls.length > 0);

    if (fetchedUrl === undefined) {
      throw new Error("Expected router.prefetch to fetch an RSC URL");
    }

    const rscUrl =
      typeof fetchedUrl === "string"
        ? fetchedUrl
        : fetchedUrl instanceof URL
          ? fetchedUrl.href
          : fetchedUrl.url;
    const cacheKey = AppElementsWire.encodeCacheKey(rscUrl, "/");

    expect(getPrefetchCache().get(cacheKey)?.outcome).toBe("pending");

    resolveResponse(new Response("flight", { headers: { "content-type": "text/x-component" } }));
    await waitForPrefetchSetup(
      () =>
        getPrefetchCache().get(cacheKey)?.outcome === "cache-seeded" &&
        getPrefetchCache().get(cacheKey)?.pending === undefined,
    );

    const entry = getPrefetchCache().get(cacheKey);
    expect(entry?.outcome).toBe("cache-seeded");
    expect(entry?.pending).toBeUndefined();

    const consumed = consumePrefetchResponse(rscUrl, "/", null);
    expect(consumed?.mountedSlotsHeader).toBeNull();
    expect(getPrefetchCache().has(cacheKey)).toBe(false);
    expect(getPrefetchedUrls().has(cacheKey)).toBe(false);
    expect(navigate).not.toHaveBeenCalled();
  });

  it("sweeps all expired entries before FIFO", () => {
    // Use fixed arbitrary values to avoid any dependency on the real wall clock
    const now = 1_000_000;
    const expired = now - PREFETCH_CACHE_TTL - 1_000; // 31s before `now`

    fillCache(MAX_PREFETCH_CACHE_SIZE, expired);
    expect(getPrefetchCache().size).toBe(MAX_PREFETCH_CACHE_SIZE);
    expect(getPrefetchedUrls().size).toBe(MAX_PREFETCH_CACHE_SIZE);

    vi.spyOn(Date, "now").mockReturnValue(now);
    storePrefetchResponse("/new.rsc", new Response("new"));

    const cache = getPrefetchCache();
    expect(cache.size).toBe(1);
    expect(cache.has("/new.rsc")).toBe(true);
    // All evicted entries should be removed from prefetched URL set
    expect(getPrefetchedUrls().size).toBe(0);
  });

  it("falls back to FIFO when all entries are fresh", () => {
    // Use fixed arbitrary values to avoid any dependency on the real wall clock
    const now = 1_000_000;

    fillCache(MAX_PREFETCH_CACHE_SIZE, now);
    expect(getPrefetchCache().size).toBe(MAX_PREFETCH_CACHE_SIZE);
    expect(getPrefetchedUrls().size).toBe(MAX_PREFETCH_CACHE_SIZE);

    vi.spyOn(Date, "now").mockReturnValue(now);
    storePrefetchResponse("/new.rsc", new Response("new"));

    const cache = getPrefetchCache();
    // FIFO evicted one, new one added → still at capacity
    expect(cache.size).toBe(MAX_PREFETCH_CACHE_SIZE);
    expect(cache.has("/new.rsc")).toBe(true);
    // First inserted entry should be evicted
    expect(cache.has("/page-0.rsc")).toBe(false);
    // Second entry should survive
    expect(cache.has("/page-1.rsc")).toBe(true);
    // FIFO-evicted entry should be removed from prefetched URL set
    expect(getPrefetchedUrls().size).toBe(MAX_PREFETCH_CACHE_SIZE - 1);
    expect(getPrefetchedUrls().has("/page-0.rsc")).toBe(false);
  });

  it("sweeps only expired entries when cache has a mix", () => {
    // Use fixed arbitrary values to avoid any dependency on the real wall clock
    const now = 1_000_000;
    const expired = now - PREFETCH_CACHE_TTL - 1_000;

    const half = Math.floor(MAX_PREFETCH_CACHE_SIZE / 2);
    const rest = MAX_PREFETCH_CACHE_SIZE - half;

    fillCache(half, expired, "/expired-");
    fillCache(rest, now, "/fresh-");
    expect(getPrefetchCache().size).toBe(MAX_PREFETCH_CACHE_SIZE);
    expect(getPrefetchedUrls().size).toBe(MAX_PREFETCH_CACHE_SIZE);

    vi.spyOn(Date, "now").mockReturnValue(now);
    storePrefetchResponse("/new.rsc", new Response("new"));

    const cache = getPrefetchCache();
    // expired swept, fresh kept, 1 new added
    expect(cache.size).toBe(rest + 1);
    expect(cache.has("/new.rsc")).toBe(true);

    // All expired entries should be gone
    for (let i = 0; i < half; i++) {
      expect(cache.has(`/expired-${i}.rsc`)).toBe(false);
    }
    // All fresh entries should survive
    for (let i = 0; i < rest; i++) {
      expect(cache.has(`/fresh-${i}.rsc`)).toBe(true);
    }
    // Only fresh entries remain in prefetched URL set
    expect(getPrefetchedUrls().size).toBe(rest);
  });

  it("does not sweep when cache is below capacity", () => {
    // Use fixed arbitrary values to avoid any dependency on the real wall clock
    const now = 1_000_000;
    const expired = now - PREFETCH_CACHE_TTL - 1_000;

    const belowCapacity = MAX_PREFETCH_CACHE_SIZE - 1;
    fillCache(belowCapacity, expired);

    vi.spyOn(Date, "now").mockReturnValue(now);
    storePrefetchResponse("/new.rsc", new Response("new"));

    const cache = getPrefetchCache();
    // Below capacity — no eviction, all entries kept + 1 new
    expect(cache.size).toBe(belowCapacity + 1);
    // storePrefetchResponse only manages the prefetch cache — the caller
    // (router.prefetch()) is responsible for adding to prefetchedUrls. So
    // the new entry (/new.rsc) is NOT in prefetchedUrls here, and the count
    // stays at belowCapacity (no evictions triggered).
    expect(getPrefetchedUrls().size).toBe(belowCapacity);
  });
});