Files
buzz/desktop/tests/e2e/scroll-history.spec.ts
cls 9dfa06ffee
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feat: import Chinese-localized Buzz source snapshot
Signed-off-by: cls_宁波本机 <908705107@qq.com>
2026-08-13 18:34:25 +08:00

2179 lines
88 KiB
TypeScript

import { expect, test } from "@playwright/test";
import { installMockBridge } from "../helpers/bridge";
// First-pass settle budget for a full channel-history prepend. CI Linux font
// rasterization can leave the restored anchor a subpixel off the local value
// (observed 28.5 vs 28), so keep headroom above the exact settle while staying
// well below a row-sized jump (~46px), which is what the real anchor-shove bug
// produces.
const CHANNEL_HISTORY_PREPEND_SETTLE_PX = 32;
async function getTimelineMetrics(page: import("@playwright/test").Page) {
return page.getByTestId("message-timeline").evaluate((element) => {
const timeline = element as HTMLDivElement;
return {
clientHeight: timeline.clientHeight,
scrollHeight: timeline.scrollHeight,
scrollTop: timeline.scrollTop,
};
});
}
async function getFirstVisibleMessage(page: import("@playwright/test").Page) {
return page.getByTestId("message-timeline").evaluate((element) => {
const timeline = element as HTMLDivElement;
const timelineRect = timeline.getBoundingClientRect();
const messages = Array.from(
timeline.querySelectorAll<HTMLElement>("[data-message-id]"),
);
for (const message of messages) {
const rect = message.getBoundingClientRect();
if (rect.bottom <= timelineRect.top || rect.top >= timelineRect.bottom) {
continue;
}
return {
id: message.dataset.messageId ?? "",
text: message.textContent?.replace(/\s+/g, " ").slice(0, 80) ?? "",
top: rect.top - timelineRect.top,
};
}
return null;
});
}
async function getMessagePosition(
page: import("@playwright/test").Page,
messageId: string,
) {
return page.getByTestId("message-timeline").evaluate((element, id) => {
const timeline = element as HTMLDivElement;
const message = timeline.querySelector<HTMLElement>(
`[data-message-id="${CSS.escape(id)}"]`,
);
if (!message) {
return null;
}
return {
id,
top:
message.getBoundingClientRect().top -
timeline.getBoundingClientRect().top,
};
}, messageId);
}
test("channel switch settles at the newest message after virtualized rows measure", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
await page.evaluate(() => {
const base = Math.floor(Date.now() / 1000);
for (let index = 0; index < 80; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `switch-bottom ${index} ${"variable-height ".repeat(
index % 7,
)}`,
createdAt: base + index,
});
}
});
// Open another channel first so this exercises a real channel switch, where
// the virtualizer API is temporarily null while the keyed list remounts.
await page.getByTestId("channel-random").click();
await expect(page.getByTestId("chat-title")).toHaveText("random");
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText("switch-bottom 79");
// Reflow a rendered row well after the removed 250ms settle deadline. The
// geometry-driven bottom intent must still chase the new physical floor.
await timeline.evaluate((element) => {
window.setTimeout(() => {
const row = element.querySelector<HTMLElement>("[data-message-id]");
if (row) {
row.style.minHeight = `${row.getBoundingClientRect().height + 240}px`;
}
element.dataset.delayedBottomReflow = "complete";
}, 600);
});
await expect(timeline).toHaveAttribute(
"data-delayed-bottom-reflow",
"complete",
);
await expect
.poll(async () => {
const metrics = await getTimelineMetrics(page);
return metrics.scrollHeight - metrics.clientHeight - metrics.scrollTop;
})
.toBeLessThanOrEqual(1);
await expect(page.getByTestId("message-scroll-to-latest")).toHaveCount(0);
});
test("first channel load paints the first window without waiting for the row-floor top-up", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
const root = window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: "cold-load root",
createdAt: 1_700_000_000,
});
if (!root) throw new Error("Failed to seed cold-load root");
for (let index = 0; index < 360; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `cold-load reply ${index}`,
parentEventId: root.id,
createdAt: 1_700_000_001 + index,
});
}
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: { ...window.__BUZZ_E2E__?.mock, channelWindowDelayMs: 5_000 },
};
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
// The reply-heavy window renders < MIN_TOP_LEVEL_ROWS_PER_FETCH top-level
// rows, which triggers the row-floor top-up — paced at 5s per page above.
// First paint must NOT wait for it: rows appear well inside that window,
// proving the top-up runs in the background rather than gating the queryFn.
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible({
timeout: 4_000,
});
// And once rows have painted, the cold-load skeleton must be gone.
await expect(timeline.locator(".t-skel-bar")).toHaveCount(0);
});
test("preserves user scroll while older channel history loads", async ({
page,
}, testInfo) => {
testInfo.setTimeout(60_000);
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
// Use the `deep-history` channel: its store is seeded with 600 messages,
// more than CHANNEL_HISTORY_LIMIT (300, hooks.ts), so the cold load windows
// to the newest 300 and leaves ~300 genuinely older messages behind the
// `until` cursor. A shallow seed (store < 300) is fully drained by the cold
// load, so the wheel `fetchOlder` returns only already-cached duplicates that
// dedup to zero net growth -- the anchor never has a real prepend to hold and
// the assertion would measure virtualizer re-measure, not scroll preservation.
await page.getByTestId("channel-deep-history").click();
await expect(page.getByTestId("chat-title")).toHaveText("deep-history");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
await page.waitForFunction(() => {
const element = document.querySelector(
'[data-testid="message-timeline"]',
) as HTMLDivElement | null;
return element && element.scrollHeight > element.clientHeight + 1000;
});
// The lowest "Deep history message #N" index currently rendered. The seed
// numbers messages 0 (oldest) .. 599 (newest), so a smaller index = older.
const oldestRenderedIndex = () =>
timeline.evaluate((element) => {
let min = Number.POSITIVE_INFINITY;
for (const row of (
element as HTMLDivElement
).querySelectorAll<HTMLElement>("[data-message-id]")) {
const match = row.textContent?.match(/#(\d+)/);
if (match) min = Math.min(min, Number(match[1]));
}
return Number.isFinite(min) ? min : null;
});
// PHASE 1 -- walk into mid-history with NO history delay. Force the timeline
// to its top and wait for an older rendered index after each fetch. A wheel
// issued while prepend restoration owns the sentinel can be swallowed, which
// made a fixed gesture loop fail before exercising the anchor invariant.
// Stop in mid-history so phase 2 still has a genuine older page to fetch above
// the reading anchor.
const scrollToTop = async () =>
timeline.evaluate((element) => {
const container = element as HTMLDivElement;
container.dispatchEvent(new WheelEvent("wheel", { deltaY: -1 }));
container.scrollTop = 0;
container.dispatchEvent(new Event("scroll", { bubbles: true }));
});
let deepest = (await oldestRenderedIndex()) ?? Number.POSITIVE_INFINITY;
for (let pageIndex = 0; pageIndex < 10 && deepest >= 400; pageIndex += 1) {
const previousDeepest = deepest;
await scrollToTop();
await expect
.poll(async () => (await oldestRenderedIndex()) ?? previousDeepest, {
timeout: 5_000,
})
.toBeLessThan(previousDeepest);
deepest = (await oldestRenderedIndex()) ?? previousDeepest;
}
expect(deepest).toBeLessThan(400);
// PHASE 2 -- now delay the next history page so it stays in flight long
// enough to observe the anchor across the landing. channelWindowDelayMs is read
// live by the bridge, so toggling it here applies to the next fetch only.
await page.evaluate(() => {
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: { ...window.__BUZZ_E2E__?.mock, channelWindowDelayMs: 1_000 },
};
(
window as unknown as { __CHANNEL_WINDOW_INFLIGHT__?: number }
).__CHANNEL_WINDOW_INFLIGHT__ = 0;
});
const inflightCount = () =>
page.evaluate(
() =>
(window as unknown as { __CHANNEL_WINDOW_INFLIGHT__?: number })
.__CHANNEL_WINDOW_INFLIGHT__ ?? 0,
);
// Snapshot the oldest rendered index BEFORE firing the delayed page, so the
// poll's growth gate can require a genuinely NEW older index after it lands.
// Wait for a concrete rendered row first: under CI load the initial rows can
// lag, leaving the scan with nothing to match (null) and a spurious failure.
await expect
.poll(async () => await oldestRenderedIndex(), { timeout: 8_000 })
.not.toBeNull();
const oldestBeforeLanding = await oldestRenderedIndex();
expect(oldestBeforeLanding).not.toBeNull();
// Move the top sentinel out of its trigger band after the phase-1 climb so
// returning to it is a fresh continuation gesture.
await page.mouse.wheel(0, 1_500);
await page.waitForTimeout(100);
// Re-enter the top sentinel and wait for the delayed request to start. Drive
// the actual scroll container because wheel input can arrive while prepend
// restoration still owns the sentinel and be discarded.
for (let attempt = 0; attempt < 50; attempt += 1) {
if ((await inflightCount()) > 0) break;
await scrollToTop();
await page.waitForTimeout(50);
}
expect(await inflightCount()).toBeGreaterThan(0);
// Capture the first-visible row id AFTER the fire wheel but WHILE the page is
// still in flight (the prepend lands ~channelWindowDelayMs later). The fire wheel
// moves the viewport, so the anchor must be read at this settled in-flight
// position -- a row captured before the fire wheel can scroll out of the
// virtualized window before the prepend lands. This row exists before the
// prepend and is the one the restore must hold.
const anchorBeforeLanding = await getFirstVisibleMessage(page);
expect(anchorBeforeLanding).not.toBeNull();
// The poll must observe the anchor holding AS a genuine older page lands
// above it. It only counts a drift reading once BOTH hold in the same sample:
// the delayed fetch has RESOLVED (inflight back to 0) AND it brought a real
// older index that was not rendered before the prepend (proof the page was
// not a duplicate-only fetch). Until then it returns Infinity and keeps
// sampling, so it cannot pass against the settled pre-landing window.
await expect
.poll(
async () => {
const [inflight, oldestNow, anchor] = await Promise.all([
inflightCount(),
oldestRenderedIndex(),
getMessagePosition(page, anchorBeforeLanding?.id ?? ""),
]);
const landed =
inflight === 0 &&
oldestNow !== null &&
oldestNow < (oldestBeforeLanding ?? 0);
if (!landed || !anchor) {
return Number.POSITIVE_INFINITY;
}
return Math.abs(anchor.top - (anchorBeforeLanding?.top ?? 0));
},
{
timeout: 8_000,
},
)
// A full channel-history page can realize content-visibility estimates over
// a few frames after the restore. Keep this below a row-sized jump while
// allowing a small first-pass settle budget.
.toBeLessThanOrEqual(CHANNEL_HISTORY_PREPEND_SETTLE_PX);
});
// Criterion 2: abandon-to-bottom mid-fetch.
//
// This catches the live-anchor vs transaction-anchor race that made the old
// design untrustworthy. The user begins an older-history fetch, then changes
// their mind and jumps back to bottom before the fetch resolves. When the
// prepended messages finally land, the timeline must remain pinned to the
// bottom -- it must NOT teleport upward to "restore" the anchor row the user
// already abandoned.
//
// Baseline note (recorded against main): this test PASSES on main. Probe
// geometry shows the existing useLoadOlderOnScroll restore would write
// scrollTop = capturedScrollTop(180) + delta(~9736) = ~9916, but the actual
// post-prepend scrollTop is at the true bottom (~29600). The bottom-stick
// guard in useTimelineScrollManager wins the race against the older-restore
// callback when the user has returned to bottom -- by accident of ordering,
// not by design. The Virtuoso replacement must keep this user-observable
// contract while removing the race-prone two-writer architecture: any
// implementation where firstItemIndex/anchor-restore can override the
// at-bottom state will fail this test. That is exactly what we want to
// prevent regressing.
//
// Black-box assertions only:
// (a) timeline geometry: scrollTop + clientHeight >= scrollHeight - 2
// (still at bottom after prepend)
// (b) the last [data-message-id] row's bottom is within 2px of the
// timeline's bottom edge (last message stayed visible at the floor)
test("does not teleport upward when user abandons fetch by jumping to bottom", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 40; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `visible current ${index}\nsecond line ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 600,
lineCount: 3,
});
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
// Setup gate: confirm the channel rendered at least one message row.
// The original draft asserted toContainText("visible current 39") --
// i.e. the last seeded message text must be in the timeline -- which
// accidentally encodes a non-virtualized contract. A Virtuoso-rendered
// timeline mounts a window of rows; the LAST seeded row may not be in
// that window if the implementation doesn't start at the bottom (which
// is itself a separate concern, validated below by `baseline` being
// pinned to scrollHeight).
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
// Pace the next history fetch so we have a deterministic window to abandon
// it. The window must be longer than the time required for the wheel-up
// step + the post-wheel waitForTimeout, otherwise the fetch resolves
// mid-wheel and the "abandon mid-fetch" semantic disappears (it becomes
// "scroll up, observe prepend land, scroll back to bottom" -- a different
// test). 5s is comfortably longer than the wheel-up loop in practice.
await page.evaluate(() => {
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: {
...window.__BUZZ_E2E__?.mock,
channelWindowDelayMs: 5_000,
},
};
});
// Wait until the timeline is scrollable before we start the dance.
await page.waitForFunction(() => {
const element = document.querySelector(
'[data-testid="message-timeline"]',
) as HTMLDivElement | null;
return element ? element.scrollHeight > element.clientHeight + 1000 : false;
});
// Start at bottom (the timeline should already be sticky-bottom on first
// load; assert it so the abandon step has a meaningful target to return to).
const baseline = await getTimelineMetrics(page);
expect(baseline.scrollTop + baseline.clientHeight).toBeGreaterThanOrEqual(
baseline.scrollHeight - 2,
);
// Scroll up to trigger the older-history fetch. We drive this through
// real wheel input rather than `scrollTop = 180; dispatchEvent("scroll")`
// because that direct-mutation pattern only works against a naive
// scroll container -- a virtualizer like Virtuoso can intercept or
// re-assert its tracked scroll position, leaving the outer element's
// scrollTop pinned to the bottom even after the write. mouse.wheel
// dispatches a real WheelEvent that whichever element owns scrolling
// must honor. Wheel up in 2000-delta chunks (the browser applies its
// own delta scaling so the actual scrolled distance is typically a
// fraction of this) until scrollTop crosses below 500 or we hit a
// step cap.
await timeline.hover();
for (let attempt = 0; attempt < 32; attempt += 1) {
const metrics = await getTimelineMetrics(page);
if (metrics.scrollTop < 500) {
break;
}
await page.mouse.wheel(0, -2000);
await page.waitForTimeout(25);
}
await page.waitForTimeout(150);
const duringFetch = await getTimelineMetrics(page);
// Sanity: we did move away from the bottom and the prepend has NOT yet
// resolved (otherwise the abandon scenario doesn't exist).
expect(duringFetch.scrollTop).toBeLessThan(500);
// "Prepend not yet resolved" tested directly via the in-flight indicator the
// suite already keys on (it renders while `isFetchingOlder` OR the prepended
// rows have not painted yet — line 127 asserts its ABSENCE at idle load). The
// older `scrollHeight <= baseline + 100` proxy assumed scrollHeight only
// changes when DOM rows are added — true for a non-virtualized list, but a
// virtualizer grows `getTotalSize()` purely from lazy row measurement (no
// prepend), so that proxy false-fails here. This signal is agnostic to how
// scrollHeight evolves.
await expect(page.getByTestId("message-timeline-fetching-older")).toHaveCount(
1,
);
// Abandon: jump back to bottom while the fetch is still in flight.
// We click the in-app "Jump to latest" button rather than writing
// scrollTop = scrollHeight directly. Same rationale as the upward
// wheel above: a virtualizer may not honor a raw scrollTop write,
// but the application's own scroll-to-bottom path is exactly what
// a real user would invoke and is part of the user-observable
// surface for both scroller implementations.
//
// The button triggers `scrollToBottom("smooth")` which animates the
// scroll, so we poll for the at-bottom condition rather than waiting
// a fixed interval. Cap at 2s; well inside our 5s channelWindowDelayMs
// window so the prepend is still in flight when this resolves.
await page.getByTestId("message-scroll-to-latest").click();
await expect
.poll(
async () => {
const m = await getTimelineMetrics(page);
return m.scrollTop + m.clientHeight >= m.scrollHeight - 2;
},
{ timeout: 2_000 },
)
.toBe(true);
const afterAbandon = await getTimelineMetrics(page);
expect(
afterAbandon.scrollTop + afterAbandon.clientHeight,
).toBeGreaterThanOrEqual(afterAbandon.scrollHeight - 2);
// Now wait for the prepend to resolve. scrollHeight grows when older
// messages land; we poll for that growth and then assert we are STILL
// at the bottom (no upward teleport to the abandoned anchor).
//
// Timeout: 12s. The wheel-up + smooth-abandon path can burn 2-3s of the
// 5s channelWindowDelayMs window before this poll begins, so the prepend may not
// land for another 2-3s. On a loaded CI runner that squeezes a tight 6s
// budget into a timeout (the prepend is a deterministic 5s mock timer, so
// the only failure mode is waiting too little); 12s leaves comfortable
// margin without weakening the assertion below.
await expect
.poll(
async () => {
const metrics = await getTimelineMetrics(page);
return metrics.scrollHeight > afterAbandon.scrollHeight + 1000
? "resolved"
: "pending";
},
{ timeout: 12_000 },
)
.toBe("resolved");
// (a) Geometry: timeline settles back to bottom. The durable bottom owner
// batches ResizeObserver-driven geometry correction into requestAnimationFrame,
// so scrollHeight growth and the physical-floor write need not share a turn.
await expect
.poll(
async () => {
const metrics = await getTimelineMetrics(page);
return (
metrics.scrollTop + metrics.clientHeight >= metrics.scrollHeight - 2
);
},
{ timeout: 2_000 },
)
.toBe(true);
// (b) DOM: the last rendered [data-message-id] sits within 2px of the
// timeline's bottom edge. This catches a class of bugs where the geometry
// looks bottom-pinned but the row landed off-screen due to padding/
// composer-spacer drift.
const lastRowOffset = await timeline.evaluate((element) => {
const t = element as HTMLDivElement;
const messages = Array.from(
t.querySelectorAll<HTMLElement>("[data-message-id]"),
);
if (messages.length === 0) {
return null;
}
const last = messages[messages.length - 1];
const timelineRect = t.getBoundingClientRect();
const rowRect = last.getBoundingClientRect();
return timelineRect.bottom - rowRect.bottom;
});
expect(lastRowOffset).not.toBeNull();
// Allow up to one composer-height worth of slack here: the composer overlay
// can legitimately float above the timeline's clientHeight floor. The
// important regression we are catching is "last row teleported hundreds
// of pixels up", not "last row sits 40px above the floor due to overlay".
// If the new design uses a Footer spacer matching composer height, this
// value should be small. We assert <= 200 to be tolerant of design choice
// while still catching teleport-class regressions.
expect(lastRowOffset as number).toBeLessThanOrEqual(200);
});
const REAL_BUZZ_BUGS_IMAGE_SHA =
"ff2862080bac3d009f97cad4bb94e6efec328eaaee058a405e854acd49fc1483";
const REAL_BUZZ_BUGS_IMAGE_URL = `https://sprout-oss.stage.blox.sqprod.co/media/${REAL_BUZZ_BUGS_IMAGE_SHA}.png`;
const REAL_BUZZ_BUGS_IMAGE_TAG = [
"imeta",
`url ${REAL_BUZZ_BUGS_IMAGE_URL}`,
"m image/png",
`x ${REAL_BUZZ_BUGS_IMAGE_SHA}`,
"size 26257",
"dim 951x244",
"filename image.png",
] as string[];
test("reserves real buzz-bugs imeta image height before image loads", async ({
page,
}) => {
await page.route("**/media/**", () => new Promise(() => {}));
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
await page.evaluate(
({ content, extraTags }) => {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content,
extraTags,
});
},
{
content: `this setting gets reverted on every update\n![image](${REAL_BUZZ_BUGS_IMAGE_URL})`,
extraTags: [REAL_BUZZ_BUGS_IMAGE_TAG],
},
);
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const image = page.getByAltText("image").last();
const rect = await image.evaluate((element) => {
const img = element as HTMLImageElement;
const box = img.getBoundingClientRect();
return {
attrHeight: img.getAttribute("height"),
attrWidth: img.getAttribute("width"),
height: box.height,
offsetHeight: img.offsetHeight,
offsetWidth: img.offsetWidth,
width: box.width,
};
});
expect(rect.attrWidth).toBe("951");
expect(rect.attrHeight).toBe("244");
expect(rect.offsetHeight).toBeGreaterThan(80);
});
// Criterion 3: target-after-backfill via deep-link.
//
// When the user opens a deep-link URL like /channels/<id>?messageId=<targetId>
// for a message that lives in older history (not in the initial render
// window), the timeline must scroll the target into view and apply the
// highlight treatment. This validates the target-resolution path independent
// of the user manually scrolling up to find the message.
//
// Black-box assertions only (per Mari's refinement):
// (a) target row's [data-message-id] is in the DOM
// (b) target row's bounding rect is inside the timeline's bounding rect
// AND within ~half a viewport of the timeline's vertical center
// (c) target row's className includes the highlight token
// ("route-target-highlight-fade") -- this is the user-visible
// highlight effect, applied via the `highlighted` prop in MessageRow
//
// No `onTargetReached` probe is used; visible-centered-highlighted is the
// stable user-observable contract.
test("deep-link to a message in older history scrolls and highlights it", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
// Seed the channel with a small live window plus a large prepended
// history block. Capture the prepended event ids so we can pick a target
// that sits well outside the initial-render window.
const prependedIds: string[] = await page.evaluate(() => {
for (let index = 0; index < 40; index += 1) {
// Monotonic createdAt so `visible current 39` (seeded last) sorts to the
// genuine last row rather than a random UUID-tiebreak position; matches
// the channel-intro seed precedent. The :630 assertion stays untouched.
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `visible current ${index}\nsecond line ${index}`,
createdAt: 1_700_000_000 + index,
});
}
const events = window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 600,
lineCount: 3,
});
return (events ?? []).map((event) => event.id);
});
expect(prependedIds.length).toBeGreaterThanOrEqual(100);
// Pick a target from the older part of the prepended block, well outside
// the 300-event cold history window. prependedIds are chronological (older
// first), so an early index remains unloaded on channel open.
const targetId = prependedIds[Math.floor(prependedIds.length / 8)];
expect(targetId).toBeTruthy();
// Open the channel via the sidebar click (same pattern as criterion-1).
// The dev server has no SPA fallback, so a direct page.goto into a deep
// /channels/<id>?messageId=<id> URL 404s, and a synthetic popstate isn't
// enough to make Tanstack Router's matcher pick up the new route. Going
// through the live UI navigation puts us inside the channel route with
// the router properly mounted; then we only need to update the search
// param to test the target-resolution contract.
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText("visible current 39");
// Now push ?messageId=<targetId> onto the existing /channels/<id> URL.
// This is the contract under test: when the route's messageId search
// param changes (which happens both on deep-link arrival and on in-app
// navigation like clicking a reply quote), the timeline must resolve the
// target, scroll to it, and apply the highlight -- even when the target
// is in not-yet-loaded older history.
//
// The app uses a hash history (createHashHistory), so the router's
// location -- pathname AND search params -- lives inside the URL hash
// fragment (#/channels/<id>?messageId=...), NOT in window.location.search.
// We must therefore rewrite the hash, not the top-level query string, or
// Tanstack Router never sees the param and targetMessageId stays null.
await page.evaluate((targetId) => {
const hash = window.location.hash.replace(/^#/, "") || "/";
const [path, query = ""] = hash.split("?");
const params = new URLSearchParams(query);
params.set("messageId", targetId);
const nextHash = `#${path}?${params.toString()}`;
window.history.pushState({}, "", `${window.location.pathname}${nextHash}`);
window.dispatchEvent(new HashChangeEvent("hashchange"));
window.dispatchEvent(new PopStateEvent("popstate"));
}, targetId);
// Wait for the target row to appear in the DOM. Note: data-message-id
// values are nostr event ids (lowercase hex), so no CSS-escape is needed
// for the Playwright locator. The `evaluate` block below runs in
// browser context and can use CSS.escape directly.
const targetRow = timeline.locator(`[data-message-id="${targetId}"]`);
await expect(targetRow).toBeVisible({ timeout: 5_000 });
// (b)/(c) Geometry + highlight. The convergence adapter re-aims the
// virtualizer across several frames (scrollToIndex on an estimated index,
// then re-resolved once rows measure), and only applies the highlight on
// the settled frame via `onConverged`. The row therefore becomes DOM-
// visible (passing `toBeVisible` above) at an intermediate overshoot
// position one or more frames before it is centered and highlighted. We
// poll the row's placement until it satisfies the full settled contract --
// centered AND carrying the highlight class -- inside the 2s highlight-fade
// window. A single synchronous read here would race the convergence loop.
const placement = await timeline.evaluate((timelineEl, id) => {
const t = timelineEl as HTMLDivElement;
return new Promise<{
rowTopRelative: number;
rowBottomRelative: number;
timelineHeight: number;
rowHeight: number;
className: string;
} | null>((resolve) => {
const deadline = performance.now() + 3_000;
const tick = () => {
const row = t.querySelector<HTMLElement>(
`[data-message-id="${CSS.escape(id)}"]`,
);
if (row) {
const tRect = t.getBoundingClientRect();
const rRect = row.getBoundingClientRect();
const result = {
rowTopRelative: rRect.top - tRect.top,
rowBottomRelative: rRect.bottom - tRect.top,
timelineHeight: tRect.height,
rowHeight: rRect.height,
className: row.className,
};
const centered =
Math.abs(
(result.rowTopRelative + result.rowBottomRelative) / 2 -
result.timelineHeight / 2,
) <=
result.timelineHeight / 2;
if (centered) {
resolve(result);
return;
}
}
if (performance.now() > deadline) {
resolve(
row
? {
rowTopRelative:
row.getBoundingClientRect().top -
t.getBoundingClientRect().top,
rowBottomRelative:
row.getBoundingClientRect().bottom -
t.getBoundingClientRect().top,
timelineHeight: t.getBoundingClientRect().height,
rowHeight: row.getBoundingClientRect().height,
className: row.className,
}
: null,
);
return;
}
requestAnimationFrame(tick);
};
tick();
});
}, targetId);
expect(placement).not.toBeNull();
const p = placement as NonNullable<typeof placement>;
// Row is inside the timeline viewport vertically.
expect(p.rowTopRelative).toBeGreaterThanOrEqual(0);
expect(p.rowBottomRelative).toBeLessThanOrEqual(p.timelineHeight + 1);
// Row's center is within half-a-viewport of the timeline's vertical center.
// This catches "scrolled but at the very top/bottom" regressions while
// tolerating different centering strategies (smooth scrollIntoView with
// block: "center" vs Virtuoso scrollToIndex({ align: "center" })).
const rowCenter = (p.rowTopRelative + p.rowBottomRelative) / 2;
const timelineCenter = p.timelineHeight / 2;
expect(Math.abs(rowCenter - timelineCenter)).toBeLessThanOrEqual(
p.timelineHeight / 2,
);
// The highlight animation is intentionally not asserted here: the route
// targets a summary wrapper when the row has thread metadata, while the
// message article remains the geometry anchor checked above.
});
// Criterion 5: search-active match enters the timeline viewport and
// carries the active-match highlight class, even when the match is far
// from the current scroll position.
//
// In a virtualized list, "active match" cannot be implemented via
// querySelector('[data-message-id=...]') + scrollIntoView, because rows
// outside the rendered window are not in the DOM. The contract this test
// pins (regardless of virtualization strategy):
//
// For any user-driven find-bar match selection, the matched row must
// enter the timeline viewport and carry the route-target-highlight-fade
// className.
//
// Test method (black-box only):
// 1. Seed the channel with a generic message bulk plus two distinct
// needles: NEEDLE-ALPHA early in the history, NEEDLE-BRAVO later.
// 2. Open the channel; user is at the bottom (most recent).
// 3. Open the find bar via Cmd/Ctrl+F. Type the ALPHA needle.
// 4. Assert: the row matching ALPHA is in the timeline viewport and
// carries the highlight class.
// 5. Replace the query with the BRAVO needle.
// 6. Assert the same two properties on the BRAVO row.
//
// Centeredness is intentionally NOT asserted -- see the comment on
// `assertInViewportAndHighlighted` below for why edge-bias is correct
// browser behavior, not a scroll regression.
//
// On main (non-virtualized) this is expected to pass: querySelector +
// scrollIntoView in MessageTimeline.tsx:165-174 finds the row because all
// loaded messages are in the DOM. The blind spot -- which this test will
// catch on the Virtuoso branch if not handled -- is recycling: any
// implementation where rows outside the rendered window are removed from
// the DOM must route active-match selection through a key->index map,
// not querySelector.
//
// Per Mari's baseline-either-way rule, recording the contract here is
// valuable even though main happens to satisfy it by construction.
test("find-bar active match scrolls and highlights row regardless of position", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
const ALPHA = "NEEDLE-ALPHA-c7b3";
const BRAVO = "NEEDLE-BRAVO-9f21";
const TOTAL = 200;
const ALPHA_INDEX = 20; // near the top after backfill
const BRAVO_INDEX = 110; // mid-channel
await page.evaluate(
({ total, alpha, bravo, alphaIndex, bravoIndex }) => {
for (let i = 0; i < total; i += 1) {
let body = `filler message ${i}`;
if (i === alphaIndex) {
body = `filler message ${i}\n${alpha}`;
} else if (i === bravoIndex) {
body = `filler message ${i}\n${bravo}`;
}
// Monotonic createdAt so ALPHA/BRAVO land at their true sorted
// positions (index 20 / 110) rather than random UUID-tiebreak slots;
// matches the channel-intro seed precedent. Needle assertions untouched.
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: body,
createdAt: 1_700_000_000 + i,
});
}
},
{
total: TOTAL,
alpha: ALPHA,
bravo: BRAVO,
alphaIndex: ALPHA_INDEX,
bravoIndex: BRAVO_INDEX,
},
);
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
// Setup gate: confirm the channel rendered at least one message row
// AND the user is at the bottom of the channel before opening the
// find bar. The original draft asserted toContainText(
// `filler message ${TOTAL - 1}`) -- i.e. the last seeded message
// text must be in the timeline -- which accidentally encodes a
// non-virtualized contract (a virtualized timeline mounts only a
// window of rows; the LAST seeded row may not be in that window).
//
// The at-bottom geometry assertion is load-bearing for this test:
// the find-bar contract is "active match scrolls a non-visible row
// into view." If the test started at a position where ALPHA was
// already mounted/visible, the scroll-into-view path would be a
// no-op and the test would pass vacuously. Pinning the start to
// the bottom of the channel guarantees the matched row is far from
// initial scroll position regardless of how the implementation
// sizes its initial render window.
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
await expect
.poll(async () => {
const m = await timeline.evaluate((el) => {
const t = el as HTMLDivElement;
return {
scrollTop: t.scrollTop,
clientHeight: t.clientHeight,
scrollHeight: t.scrollHeight,
};
});
return m.scrollTop + m.clientHeight >= m.scrollHeight - 2;
})
.toBe(true);
// Open the find bar. The shortcut handler uses platform-standard
// primary modifier (Meta on macOS, Control elsewhere). Playwright's
// ControlOrMeta abstracts this for us.
await page.keyboard.press("ControlOrMeta+f");
await expect(page.getByTestId("channel-find-bar")).toBeVisible();
const input = page.getByPlaceholder("Find in channel");
// Poll for the row matching `needle` to settle inside the timeline
// viewport, then return its placement + className. Polling is required
// because the find-bar -> active-match -> scrollIntoView path is async
// (state update, then a smooth scroll). Locator `toBeVisible` only
// checks DOM-visible (display/visibility), not in-viewport, so it
// can't be used as the wait condition for "the scroll completed".
//
// Tolerance: 1px on each edge for sub-pixel rounding. The 5s budget
// accommodates browsers honoring smooth-scroll over long distances
// (initial scroll position is the bottom of a 200-message channel;
// the ALPHA row is ~180 rows up).
const waitForRowInViewport = async (needle: string) =>
timeline.evaluate((timelineEl, n) => {
return new Promise<{
rowTopRelative: number;
rowBottomRelative: number;
timelineHeight: number;
className: string;
}>((resolve, reject) => {
const deadline = performance.now() + 5_000;
const t = timelineEl as HTMLDivElement;
const tick = () => {
const rows = Array.from(
t.querySelectorAll<HTMLElement>("[data-message-id]"),
);
const row = rows.find((r) => r.textContent?.includes(n)) ?? null;
if (row) {
const tRect = t.getBoundingClientRect();
const rRect = row.getBoundingClientRect();
const top = rRect.top - tRect.top;
const bottom = rRect.bottom - tRect.top;
const height = tRect.height;
if (top >= -1 && bottom <= height + 1) {
resolve({
rowTopRelative: top,
rowBottomRelative: bottom,
timelineHeight: height,
className: row.className,
});
return;
}
}
if (performance.now() > deadline) {
reject(
new Error(
`row matching "${n}" did not enter timeline viewport within 5s`,
),
);
return;
}
requestAnimationFrame(tick);
};
tick();
});
}, needle);
const assertInViewportAndHighlighted = (placement: {
rowTopRelative: number;
rowBottomRelative: number;
timelineHeight: number;
className: string;
}) => {
// User-observable contract: row enters the timeline's own viewport and
// carries the active-match highlight class. We intentionally do NOT
// assert centeredness: `scrollIntoView({ block: 'center' })` legitimately
// biases toward a list edge when the target is near the start or end
// (e.g., the ALPHA index-20 row of a 200-message channel lands at the
// top because the browser cannot center an item that has fewer rows
// above it than half the viewport). Near-edge bias is correct browser
// behavior, not a scroll-contract regression; tightening on
// centeredness here would couple the test to scroll-anchor heuristics
// rather than the user-observable invariant.
expect(placement.rowTopRelative).toBeGreaterThanOrEqual(-1);
expect(placement.rowBottomRelative).toBeLessThanOrEqual(
placement.timelineHeight + 1,
);
expect(placement.className).toContain("route-target-highlight-fade");
};
// --- Phase 1: ALPHA ---
await input.fill(ALPHA);
// Sanity check: the active match should resolve and the matching row
// should land in the DOM. visibility != in-viewport here -- we follow
// up with `waitForRowInViewport` to enforce the placement contract.
const alphaRow = timeline.locator(`[data-message-id]`).filter({
hasText: ALPHA,
});
await expect(alphaRow).toBeVisible({ timeout: 5_000 });
const a = await waitForRowInViewport(ALPHA);
assertInViewportAndHighlighted(a);
// --- Phase 2: BRAVO ---
// Replace the query. The active-match id changes, which should drive
// a fresh scroll + highlight on the BRAVO row.
await input.fill(BRAVO);
const bravoRow = timeline.locator(`[data-message-id]`).filter({
hasText: BRAVO,
});
await expect(bravoRow).toBeVisible({ timeout: 5_000 });
const b = await waitForRowInViewport(BRAVO);
assertInViewportAndHighlighted(b);
});
// Criterion 6 (composer half): expanding the composer (multi-line input)
// must not push the bottom row out of the user-visible area of the
// timeline when the user is following the bottom. On main the composer
// is rendered as an overlay (`absolute inset-x-0 bottom-0`) on top of
// the timeline, and the timeline reserves bottom padding to keep the
// last message clear of the composer. The contract this test pins
// (regardless of overlay-vs-sibling layout strategy):
//
// While the user is at the bottom of the timeline, growing the
// composer from one line to several lines must keep the last
// message's bottom edge at-or-above the composer's top edge
// (within a small tolerance). The bottom row must not slide
// underneath the composer chrome.
//
// Test method (black-box only):
// 1. Seed the channel with enough messages to make the timeline
// scrollable. The last message text is unique so we can address
// it.
// 2. Open the channel. The view starts at the bottom by default.
// 3. Record the gap between the last message's bottom edge and the
// composer's top edge. The bottom row must sit at-or-above the
// composer top (gap >= 0).
// 4. Focus the composer and press Shift+Enter several times to grow
// it into a multi-line state.
// 5. Wait for the composer to actually grow (its bounding rect grows
// taller, equivalently its top moves up).
// 6. Assert the bottom-row-to-composer-top gap is still >= 0
// (within tolerance). The timeline must have either auto-scrolled
// to follow output or kept enough bottom padding to clear the
// enlarged composer.
//
// Tolerance: 4px. Accounts for sub-pixel rendering and a single rAF
// of lag between composer resize and follow-output. We intentionally
// don't require equality -- the invariant is "the user can still see
// the bottom row clear of composer chrome," not "glued to a specific
// pixel."
test("composer expansion does not push bottom row out of viewport", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
// Seed enough messages that the timeline is scrollable. The bottom
// message has a distinct text so we can resolve its row even if the
// virtualizer recycles surrounding rows.
const TOTAL = 60;
const BOTTOM_NEEDLE = "BOTTOM-NEEDLE-3a91";
await page.evaluate(
({ total, bottom }) => {
for (let i = 0; i < total; i += 1) {
const body = i === total - 1 ? bottom : `filler message ${i}`;
// Monotonic createdAt: without it all rows share one whole-second
// stamp and `sortMessages` tiebreaks by random UUID, so BOTTOM_NEEDLE
// (seeded last) lands at a random sorted index — often outside the
// virtualized window, so `toContainText(BOTTOM_NEEDLE)` flakes. A
// distinct stamp per row sorts the needle to the true last row.
// Matches the channel-intro seed precedent (1_700_000_001 + index).
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: body,
createdAt: 1_700_000_000 + i,
});
}
},
{ total: TOTAL, bottom: BOTTOM_NEEDLE },
);
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText(BOTTOM_NEEDLE);
// Geometry probe: report the gap between the bottom row's bottom edge
// and the composer's top edge, plus the composer's own height so we
// can verify the composer-driven growth separately.
const probe = async () =>
page.evaluate((needle) => {
const t = document.querySelector<HTMLDivElement>(
'[data-testid="message-timeline"]',
);
const c = document.querySelector<HTMLElement>(
'[data-testid="message-composer"]',
);
if (!t || !c) {
return { found: false as const };
}
const rows = Array.from(
t.querySelectorAll<HTMLElement>("[data-message-id]"),
);
const bottomRow = rows.find((r) => r.textContent?.includes(needle));
if (!bottomRow) {
return { found: false as const };
}
const rRect = bottomRow.getBoundingClientRect();
const cRect = c.getBoundingClientRect();
return {
found: true as const,
// Positive or zero means the row's bottom sits at-or-above
// the composer's top. Negative means the row has been pushed
// underneath the composer overlay.
gapAboveComposer: cRect.top - rRect.bottom,
composerHeight: cRect.height,
};
}, BOTTOM_NEEDLE);
const before = await probe();
expect(before.found).toBe(true);
if (!before.found) return;
// Sanity: starting state has the bottom row clear of the composer.
expect(before.gapAboveComposer).toBeGreaterThanOrEqual(-4);
// Grow the composer. Shift+Enter inserts a hard break in the Tiptap
// editor without sending; six line breaks plus typed text reliably
// grows the composer past its single-line min-height. The inner
// editor scroll container is height-capped at max-h-32, so growth
// stops at ~one extra row of UI height after the cap is reached --
// that's still enough to verify the contract: even modest composer
// growth must not occlude the bottom row.
const input = page.getByTestId("message-input");
await input.click();
for (let i = 0; i < 6; i += 1) {
await page.keyboard.type(`line ${i}`);
await page.keyboard.press("Shift+Enter");
}
await page.keyboard.type("line 6");
// Wait for the composer growth to propagate through layout. The
// composer's outer bounding height must visibly grow. This is the
// smallest sanity guard against the test tautologically passing
// when the composer didn't actually grow (e.g., focus failed).
await expect
.poll(
async () => {
const p = await probe();
return p.found ? p.composerHeight : Number.NaN;
},
{ timeout: 5_000 },
)
.toBeGreaterThan(before.composerHeight + 4);
// The invariant: bottom row must still be clear of the composer
// overlay. Either the timeline auto-scrolled to follow output, or
// the reserved bottom padding grew with the composer. Both are
// acceptable user-observable states.
const after = await probe();
expect(after.found).toBe(true);
if (!after.found) return;
expect(after.gapAboveComposer).toBeGreaterThanOrEqual(-4);
});
// Regression: Virtua's mounted range must cover the full GUI plane in both
// scroll directions. The composer overlays the timeline; it is not the bottom
// of the viewport. In particular, rows behind it must not retire early when an
// upward scroll settles at the same offset as a downward scroll.
test("mounted rows cover the viewport beneath the composer in both directions", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 120; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `direction row ${index}\nsecond line ${index}`,
createdAt: 1_700_000_000 + index,
});
}
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText("direction row 119");
await page.waitForFunction(() => {
const element = document.querySelector<HTMLDivElement>(
'[data-testid="message-timeline"]',
);
return element && element.scrollHeight > element.clientHeight * 3;
});
const settleAtTargetFrom = async (startFraction: number) => {
await timeline.evaluate((element, fraction) => {
const maxOffset = element.scrollHeight - element.clientHeight;
element.scrollTop = maxOffset * fraction;
element.dispatchEvent(new Event("scroll", { bubbles: true }));
}, startFraction);
await page.waitForTimeout(100);
await timeline.evaluate((element) => {
const maxOffset = element.scrollHeight - element.clientHeight;
element.scrollTop = maxOffset / 2;
element.dispatchEvent(new Event("scroll", { bubbles: true }));
});
await expect
.poll(() =>
timeline.evaluate((element) => {
const maxOffset = element.scrollHeight - element.clientHeight;
return Math.abs(element.scrollTop - maxOffset / 2);
}),
)
.toBeLessThan(100);
};
const mountedCoverage = () =>
timeline.evaluate((element) => {
const viewport = element.getBoundingClientRect();
const mountedRows = Array.from(
element.querySelectorAll<HTMLElement>("[data-message-id]"),
);
return {
above: viewport.top - mountedRows[0].getBoundingClientRect().top,
below:
mountedRows[mountedRows.length - 1].getBoundingClientRect().bottom -
viewport.bottom,
viewportHeight: viewport.height,
};
});
// Arrive from below (upward scroll), then from above (downward scroll). At
// either settle, mounted message geometry must reach the actual viewport
// bottom, beyond the overlaid composer's top edge. It must also retain at
// least one full viewport of already-rendered rows on both sides.
await settleAtTargetFrom(0.75);
await expect
.poll(async () => {
const coverage = await mountedCoverage();
return Math.min(coverage.above, coverage.below) / coverage.viewportHeight;
})
.toBeGreaterThanOrEqual(1);
await settleAtTargetFrom(0.25);
await expect
.poll(async () => {
const coverage = await mountedCoverage();
return Math.min(coverage.above, coverage.below) / coverage.viewportHeight;
})
.toBeGreaterThanOrEqual(1);
});
// Regression: after a real prepend, Virtua's `shift` instruction must not stay
// enabled while the reader later fast-scrolls through the middle of the list.
// A stale shifted range can stop with no mounted row covering part of the
// viewport and remain blank until another scroll event. The idle samples below
// deliberately dispatch no follow-up scroll.
test("fast middle-page scroll settles with continuous mounted coverage", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 180; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `settle row ${index}\nline two ${index}\nline three ${index}`,
createdAt: 1_700_000_000 + index,
});
}
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText("settle row 179");
await page.waitForFunction(() => {
const element = document.querySelector<HTMLDivElement>(
'[data-testid="message-timeline"]',
);
return element && element.scrollHeight > element.clientHeight * 3;
});
// Land a genuine prepend first. This is what turns `shift` on; subsequent
// ordinary list updates and measurements must happen with it cleared.
const scrollHeightBeforePrepend = (await getTimelineMetrics(page))
.scrollHeight;
await page.evaluate(() => {
for (let index = 0; index < 100; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `prepended settle row ${index}\nolder line two ${index}\nolder line three ${index}`,
createdAt: 1_699_999_000 + index,
});
}
});
await expect
.poll(() =>
getTimelineMetrics(page).then((metrics) => metrics.scrollHeight),
)
.toBeGreaterThan(scrollHeightBeforePrepend + 2_000);
// Simulate a fast trackpad pass through several middle-page ranges, then
// stop. The final evaluate emits the last scroll event; all coverage samples
// after it are passive observations.
await timeline.evaluate((element) => {
const maxOffset = element.scrollHeight - element.clientHeight;
for (const fraction of [0.72, 0.28, 0.64, 0.36, 0.58, 0.44, 0.52]) {
element.scrollTop = maxOffset * fraction;
element.dispatchEvent(new Event("scroll", { bubbles: true }));
}
});
await page.waitForTimeout(250);
const viewportCoverage = () =>
timeline.evaluate((element) => {
const viewport = element.getBoundingClientRect();
const rows = Array.from(
element.querySelectorAll<HTMLElement>("[data-message-id]"),
)
.map((row) => row.getBoundingClientRect())
.filter(
(rect) => rect.bottom > viewport.top && rect.top < viewport.bottom,
)
.sort((left, right) => left.top - right.top);
if (rows.length === 0) return Number.POSITIVE_INFINITY;
let cursor = viewport.top;
let largestGap = Math.max(0, rows[0].top - viewport.top);
for (const row of rows) {
largestGap = Math.max(largestGap, row.top - cursor);
cursor = Math.max(cursor, row.bottom);
}
return Math.max(largestGap, viewport.bottom - cursor);
});
// A day heading can produce a small legitimate gap between message rows;
// the stale-range failure leaves a viewport-scale hole. Check repeatedly
// while idle so a transient good frame cannot mask a stuck blank range.
for (let sample = 0; sample < 5; sample += 1) {
expect(await viewportCoverage()).toBeLessThan(100);
await page.waitForTimeout(100);
}
});
// Criterion 8: in-viewport content resize while scrolled up preserves the
// anchor row's position.
//
// The hook owns scroll position via `useAnchoredScroll`. When the user is
// scrolled up reading older history and a row *above* their reading row
// reflows (image decode without reserved dim metadata, link-card load,
// async embed expand, late font load, markdown that expands), the rows
// below shift on them. Before this test landed, the ResizeObserver only
// re-pinned when stuck-to-bottom; the scrolled-up case had no correction.
//
// The fix: the ResizeObserver calls the same anchor-restore primitive as
// the post-commit layout effect when anchored to a message. This test
// reproduces the scenario without touching React state — it directly
// grows a DOM row's height via a style override, which is exactly the
// kind of layout shift that previously had no correction (the messages
// array is unchanged, so the React layout effect never runs).
//
// Black-box assertions: the anchor row's top within the timeline must be
// unchanged (within 2px) before and after the synthetic above-anchor
// height growth.
test("in-viewport reflow above the anchor row does not push it down", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
// Seed enough rows that the timeline becomes scrollable with several
// rows above whatever we anchor to.
await page.evaluate(() => {
for (let index = 0; index < 60; index += 1) {
// Monotonic createdAt so `resize-anchor row 59` (seeded last) sorts to
// the genuine last row rather than a random UUID-tiebreak position; see
// the composer seed for the full rationale.
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `resize-anchor row ${index}\nsecond line ${index}\nthird line ${index}`,
createdAt: 1_700_000_000 + index,
});
}
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline).toContainText("resize-anchor row 59");
// Wait until the timeline is genuinely scrollable.
await page.waitForFunction(() => {
const element = document.querySelector(
'[data-testid="message-timeline"]',
) as HTMLDivElement | null;
return element && element.scrollHeight > element.clientHeight + 800;
});
await expect
.poll(async () => {
const metrics = await getTimelineMetrics(page);
return metrics.scrollHeight - metrics.clientHeight - metrics.scrollTop;
})
.toBeLessThanOrEqual(1);
// Let the virtualizer's two-frame initial bottom positioning retire before
// issuing reader input; otherwise that mount-only rAF can overwrite the
// first wheel in the same frame.
await page.waitForTimeout(100);
// Use real input so the virtualizer observes and owns the offset change. A
// raw `scrollTop` write can leave its internal offset pinned to the bottom;
// the next row measurement then legitimately reconciles back to that floor.
await timeline.hover();
for (let attempt = 0; attempt < 12; attempt += 1) {
const metrics = await getTimelineMetrics(page);
const target = metrics.scrollHeight / 2;
if (Math.abs(metrics.scrollTop - target) <= 100) break;
await page.mouse.wheel(0, target - metrics.scrollTop);
await page.waitForTimeout(25);
}
await page.waitForTimeout(50);
// Capture the anchor row (top-crossing) and its baseline top within
// the timeline. This is the row the user is reading.
const baseline = await getFirstVisibleMessage(page);
expect(baseline).not.toBeNull();
if (!baseline) return;
// Find a rendered row *above* the anchor and grow its height. This
// mimics an in-viewport reflow (image decode, embed expansion) that
// does NOT change the messages array, so the React layout effect
// would not fire. The ResizeObserver is the only path that can
// correct the resulting shift.
const growthApplied = await timeline.evaluate((element, anchorId) => {
const t = element as HTMLDivElement;
const rows = Array.from(
t.querySelectorAll<HTMLElement>("[data-message-id]"),
);
const anchorIndex = rows.findIndex(
(row) => row.dataset.messageId === anchorId,
);
if (anchorIndex <= 0) return false;
// Pick a row a few above the anchor so the growth is clearly above
// the reader's eye, not at it.
const target = rows[Math.max(0, anchorIndex - 3)];
if (!target) return false;
// 80px is well above the 0.5px noise floor in restoreAnchorToMessage
// and large enough to be a visible jump if uncorrected.
const currentHeight = target.getBoundingClientRect().height;
target.style.minHeight = `${currentHeight + 80}px`;
return true;
}, baseline.id);
expect(growthApplied).toBe(true);
// ResizeObserver callbacks run asynchronously after layout. Poll the
// anchor row's position; it must converge back to (or stay at) its
// baseline top within ~2px.
await expect
.poll(
async () => {
const current = await getMessagePosition(page, baseline.id);
return current
? Math.abs(current.top - baseline.top)
: Number.POSITIVE_INFINITY;
},
{ timeout: 3_000 },
)
.toBeLessThanOrEqual(2);
});
// Regression: the channel intro ("header") must never flash mid-content while
// an older-history page is still loading. Reproduces the reported bug where the
// header appeared in the middle of history during pagination. The companion
// "scrollable channel ... hides intro actions until top" test in channels.spec
// already proves the positive (intro shows once at the true, exhausted top);
// this proves the negative (it stays hidden while a fetch is in flight).
//
// Uses real wheel input, not `scrollTop = 0`, because the timeline is
// virtualized (Virtuoso) and re-asserts its tracked scroll position after a
// raw scrollTop write -- see the abandon test above for the same rationale.
test("channel intro stays hidden while older history is loading", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 40; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `visible current ${index}\nsecond line ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 600,
lineCount: 3,
});
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
// Pace the older fetch so it stays in flight long enough to assert against.
await page.evaluate(() => {
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: {
...window.__BUZZ_E2E__?.mock,
channelWindowDelayMs: 5_000,
},
};
});
await page.waitForFunction(() => {
const element = document.querySelector(
'[data-testid="message-timeline"]',
) as HTMLDivElement | null;
return element ? element.scrollHeight > element.clientHeight + 1000 : false;
});
// At the bottom on initial open: intro hidden.
await expect(page.getByTestId("message-channel-intro")).toHaveCount(0);
// Wheel up to the top to trigger the (5s-delayed) older fetch.
await timeline.hover();
for (let attempt = 0; attempt < 32; attempt += 1) {
const metrics = await getTimelineMetrics(page);
if (metrics.scrollTop < 500) {
break;
}
await page.mouse.wheel(0, -2000);
await page.waitForTimeout(25);
}
await page.waitForTimeout(150);
// We are near the top of the loaded window AND the prepend has not resolved
// (history is still in flight). The intro MUST stay hidden -- this is the
// mid-load flash the fix prevents.
const duringFetch = await getTimelineMetrics(page);
expect(duringFetch.scrollTop).toBeLessThan(500);
await expect(page.getByTestId("message-channel-intro")).toHaveCount(0);
// It must remain hidden while the fetch indicator is visible. Once the
// delayed fetch completes, the channel may legitimately be at the true start
// and show the intro.
await expect
.poll(
async () => {
const introCount = await page
.getByTestId("message-channel-intro")
.count();
const indicatorCount = await page
.getByTestId("message-timeline-fetching-older")
.count();
if (indicatorCount > 0 && introCount > 0) {
return "intro-appeared-during-fetch";
}
return indicatorCount === 0 ? "resolved" : "pending";
},
{ timeout: 7_000 },
)
.toBe("resolved");
});
// Regression for the architectural bug Wes reported: in a channel with MORE
// content events than the timeline window cap (MAX_TIMELINE_MESSAGES = 2000),
// scrolling back must keep paginating older history WITHOUT ever flashing the
// channel intro ("header") mid-content. The old code inferred exhaustion from a
// post-merge oldest-timestamp compare; once the cap evicted a freshly-prepended
// older root, that compare wrongly fired `hasOlderMessages=false`, popping the
// header and then flooding in a batch. This test crosses the cap on purpose and
// asserts the header stays hidden while genuine older history still loads.
test("channel intro stays hidden while paginating past the timeline cap", async ({
page,
}, testInfo) => {
testInfo.setTimeout(90_000);
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
// Seed past the 2000-event cap: a current window plus ~2100 older roots.
// Crossing the cap is the whole point — the prepend must NOT evict the loaded
// roots in a way that falsely signals "channel start reached".
await page.evaluate(() => {
for (let index = 0; index < 60; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `recent ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 2100,
lineCount: 2,
});
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
// At the bottom on open: intro hidden.
await expect(page.getByTestId("message-channel-intro")).toHaveCount(0);
// Scroll back until pagination reaches the true channel start (the oldest
// seeded root, "mock older 0") or clearly stalls. Each pass triggers an
// older-history fetch; we wait for it to settle (oldest rendered id advances)
// before the next wheel. The intro must never appear while older roots remain.
//
// With the old newest-2000 cap, the freshly-prepended older roots are evicted
// once the cache crosses MAX_TIMELINE_MESSAGES, so the oldest rendered row
// cannot advance past the window boundary — the loop stalls well above index
// 0. The fixed cap retains backward-paged roots, so it reaches the start.
const oldestRenderedIndex = async () =>
page.getByTestId("message-timeline").evaluate((element) => {
const rows = (element as HTMLDivElement).querySelectorAll<HTMLElement>(
"[data-message-id]",
);
let min = Number.POSITIVE_INFINITY;
for (const row of rows) {
const match = row.textContent?.match(/mock older (\d+)/);
if (match) min = Math.min(min, Number(match[1]));
}
return Number.isFinite(min) ? min : null;
});
const isIntroHeaderInViewport = async () =>
page.getByTestId("message-timeline").evaluate((timelineElement) => {
const icon = timelineElement.querySelector<HTMLElement>(
'[data-testid="message-channel-intro-icon"]',
);
if (!icon) return false;
const timelineRect = timelineElement.getBoundingClientRect();
const iconRect = icon.getBoundingClientRect();
return (
iconRect.bottom > timelineRect.top && iconRect.top < timelineRect.bottom
);
});
// Poll for real progress instead of a fixed sleep: a slow CI shard's fetch
// round-trip outlasts a hard delay and reads as a false stall.
const waitForOlderHistoryProgress = async (previousDeepest: number) => {
try {
await expect
.poll(async () => (await oldestRenderedIndex()) ?? previousDeepest, {
timeout: 10_000,
})
.toBeLessThan(previousDeepest);
} catch {
// No advancement within the window: treat as a stall, not a failure.
}
return oldestRenderedIndex();
};
// Drive scrollTop to 0 each pass instead of `mouse.wheel`: the older-history
// sentinel disconnects while a prepend's index-restore owns scroll and only
// re-arms once it settles, so a wheel issued during that window is swallowed
// and reads as a false stall. Forcing the top guarantees the re-armed
// sentinel re-fires and the next older page fetches.
const scrollToTop = async () =>
timeline.evaluate((element) => {
const container = element as HTMLDivElement;
container.dispatchEvent(new WheelEvent("wheel", { deltaY: -1 }));
container.scrollTop = 0;
container.dispatchEvent(new Event("scroll", { bubbles: true }));
});
await timeline.hover();
let deepest = Number.POSITIVE_INFINITY;
let stallStreak = 0;
for (let attempt = 0; attempt < 200 && deepest > 0; attempt += 1) {
await scrollToTop();
const current = await waitForOlderHistoryProgress(deepest);
if ((current ?? Number.POSITIVE_INFINITY) > 50) {
expect(await isIntroHeaderInViewport()).toBe(false);
}
if (current !== null && current < deepest) {
deepest = current;
stallStreak = 0;
} else {
// No advance within the 10s settle window. `waitForOlderHistoryProgress`
// already absorbs a slow fetch round-trip, so each no-advance pass is a
// genuine miss (sentinel still owned, or true end-of-history). Allow a
// generous streak before bailing so a few owned-window passes near the
// start can't end the loop short of index 0.
stallStreak += 1;
if (stallStreak > 15) break;
}
}
// Reached deep history (near the true start) without the cap evicting the
// backward-paged roots. < 50 leaves slack for virtualization not rendering
// the literal index-0 row at the exact top.
expect(deepest).toBeLessThan(50);
});
// Regression for the flood Wes reported: scrolling back while an older-history
// fetch is already in flight must NOT queue a second concurrent visible page
// fetch. Aux backfills also use `get_channel_window` continuation requests, so the e2e bridge
// probe counts only visible older-page requests (`until` and not `#e`).
test("older-history fetches never overlap (no concurrent in-flight requests)", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 60; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `recent ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 1200,
lineCount: 2,
});
(
window as unknown as { __CHANNEL_WINDOW_INFLIGHT_PEAK__?: number }
).__CHANNEL_WINDOW_INFLIGHT_PEAK__ = 0;
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: { ...window.__BUZZ_E2E__?.mock, channelWindowDelayMs: 400 },
};
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
await timeline.hover();
await timeline.evaluate((element) => {
const timelineElement = element as HTMLDivElement;
timelineElement.scrollTop = 150;
timelineElement.dispatchEvent(new Event("scroll", { bubbles: true }));
});
await expect(page.getByTestId("message-timeline-fetching-older")).toBeVisible(
{ timeout: 2_000 },
);
for (let attempt = 0; attempt < 40; attempt += 1) {
await page.mouse.wheel(0, -3000);
await page.waitForTimeout(50);
}
await page.waitForTimeout(800);
const peak = await page.evaluate(
() =>
(window as unknown as { __CHANNEL_WINDOW_INFLIGHT_PEAK__?: number })
.__CHANNEL_WINDOW_INFLIGHT_PEAK__ ?? 0,
);
expect(peak).toBeLessThanOrEqual(1);
});
// Regression for Wes's "I only see the loading indicator sometimes": the
// older-fetch spinner used to be an in-flow element at content-top, so it
// scrolled out of view the moment the reader was anywhere but the very top.
// It must be pinned to the viewport so it's visible while a backward fetch is
// in flight regardless of scroll position.
test("older-history spinner stays visible in viewport while fetching mid-scroll", async ({
page,
}) => {
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 60; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `recent ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 1200,
lineCount: 2,
});
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: { ...window.__BUZZ_E2E__?.mock, channelWindowDelayMs: 2_000 },
};
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
// Trigger the older fetch near the top, then move the reader mid-scroll
// while the fetch is still in flight. Set scrollTop directly instead of
// mouse.wheel: wheel deltas vary across CI environments and can land the
// timeline at scrollTop 0, which is the one position this test must avoid.
await timeline.evaluate((element) => {
const timelineElement = element as HTMLDivElement;
timelineElement.scrollTop = 150;
timelineElement.dispatchEvent(new Event("scroll", { bubbles: true }));
});
const indicator = page.getByTestId("message-timeline-fetching-older");
await expect(indicator).toBeVisible({ timeout: 2_000 });
await timeline.evaluate((element) => {
const timelineElement = element as HTMLDivElement;
timelineElement.scrollTop = timelineElement.clientHeight;
timelineElement.dispatchEvent(new Event("scroll", { bubbles: true }));
});
await expect(indicator).toBeVisible();
const { scrollTop } = await getTimelineMetrics(page);
expect(scrollTop).toBeGreaterThan(8);
const withinViewport = await page.evaluate(() => {
const timelineEl = document.querySelector<HTMLElement>(
'[data-testid="message-timeline"]',
);
const spinnerEl = document.querySelector<HTMLElement>(
'[data-testid="message-timeline-fetching-older"]',
);
if (!timelineEl || !spinnerEl) return false;
const t = timelineEl.getBoundingClientRect();
const s = spinnerEl.getBoundingClientRect();
return s.top >= t.top - 1 && s.bottom <= t.bottom + 1;
});
expect(withinViewport).toBe(true);
});
// Regression for Wes's "scroll to the top once and it loads the WHOLE channel":
// a single scroll-up gesture must page older history ONCE (a bounded step), not
// cascade page-after-page to the channel start with no further user scroll. The
// cascade came from the load-older observer disconnecting and recreating itself
// after each fetch — the fresh observer re-reported the still-intersecting
// sentinel and re-fired immediately. A persistent observer only re-fires when
// the sentinel re-enters the top band, i.e. on a NEW scroll gesture.
//
// Distinct from the "never overlap" test (which asserts no CONCURRENT in-flight
// fetches): a cascade keeps peak in-flight at 1 while firing many SEQUENTIAL
// pages. This asserts the cumulative fetch count stays bounded after one
// gesture, and the timeline does not dig to the oldest seeded root on its own.
test("one scroll-up gesture pages older history once, not to the channel top", async ({
page,
}, testInfo) => {
testInfo.setTimeout(60_000);
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
// Deep seed: a current window plus ~1200 older roots, far more than a single
// older page yields. If pagination auto-cascades, it will dig all the way to
// "mock older 0"; if it pages once per gesture, it stops well short.
await page.evaluate(() => {
for (let index = 0; index < 60; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `recent ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 1200,
lineCount: 2,
});
(
window as unknown as { __CHANNEL_WINDOW_FETCH_COUNT__?: number }
).__CHANNEL_WINDOW_FETCH_COUNT__ = 0;
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
// Fifty compact continuation rows overflow this viewport by ~986px after
// day-heading folding, so visibility is the settled cold-window gate. The
// gesture below still traverses the entire overflow and the assertions prove
// bounded paging directly.
// The cold load may itself page once to fill the row floor; ignore anything
// before the user gesture by resetting the counter at the settled bottom.
await page.evaluate(() => {
(
window as unknown as { __CHANNEL_WINDOW_FETCH_COUNT__?: number }
).__CHANNEL_WINDOW_FETCH_COUNT__ = 0;
});
const fetchCount = () =>
page.evaluate(
() =>
(window as unknown as { __CHANNEL_WINDOW_FETCH_COUNT__?: number })
.__CHANNEL_WINDOW_FETCH_COUNT__ ?? 0,
);
const oldestRenderedIndex = () =>
timeline.evaluate((element) => {
let min = Number.POSITIVE_INFINITY;
for (const row of (
element as HTMLDivElement
).querySelectorAll<HTMLElement>("[data-message-id]")) {
const match = row.textContent?.match(/mock older (\d+)/);
if (match) min = Math.min(min, Number(match[1]));
}
return Number.isFinite(min) ? min : null;
});
// ONE scroll-up gesture to the top band, then HANDS OFF. A single wheel tick
// is enough to bring the sentinel into the 200px rootMargin.
await timeline.hover();
await page.mouse.wheel(0, -4000);
// Let any cascade run unimpeded for a generous window. With the bug, the
// observer re-arms after each page and digs through all ~1200 older roots in
// this window; with the fix it pages once and waits for the next gesture.
await page.waitForTimeout(2_500);
const pagesFetched = await fetchCount();
const deepest = await oldestRenderedIndex();
// One gesture should yield a small, bounded number of pages — not dozens.
// pageOlderMessagesUntilRowFloor may fetch up to MAX_BATCHES_PER_FETCH (3)
// relay pages to satisfy one visible row floor, so allow that ceiling plus a
// little slack; a cascade blows far past it.
expect(pagesFetched).toBeLessThanOrEqual(4);
// And it must NOT have reached the oldest seeded root on its own.
expect(deepest ?? Number.POSITIVE_INFINITY).toBeGreaterThan(50);
});
// Regression for Wes's "after a page loads I'm yanked to the oldest of the new
// page instead of staying where I was reading" (event 6, timeline-scroll-rework
// thread). De-virtualizing the list re-enabled native `overflow-anchor`, but the
// browser does NOT scroll-anchor an older-history prepend at the top edge (no
// anchor node above the viewport at scrollTop ~0). The reading row must stay
// fixed across the prepend; the JS anchor restore in useAnchoredScroll owns it.
test("older-history prepend keeps the reading row fixed (no jump to oldest)", async ({
page,
}, testInfo) => {
testInfo.setTimeout(60_000);
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() =>
typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function" &&
typeof window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__ === "function",
);
await page.evaluate(() => {
for (let index = 0; index < 40; index += 1) {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "general",
content: `recent ${index}`,
});
}
window.__BUZZ_E2E_PREPEND_MOCK_HISTORY__?.({
channelName: "general",
count: 1200,
lineCount: 2,
});
});
await page.getByTestId("channel-general").click();
await expect(page.getByTestId("chat-title")).toHaveText("general");
const timeline = page.getByTestId("message-timeline");
await expect(timeline.locator("[data-message-id]").first()).toBeVisible();
await page.waitForFunction(() => {
const element = document.querySelector(
'[data-testid="message-timeline"]',
) as HTMLDivElement | null;
return element ? element.scrollHeight > element.clientHeight + 1000 : false;
});
// Pace the older fetch BEFORE scrolling up, so the very first older page the
// top sentinel triggers stays in flight long enough to read the anchor before
// and after it lands. The cold window leaves older roots behind the composite
// cursor, so one scroll-up to the top band fires a genuine page.
await page.evaluate(() => {
window.__BUZZ_E2E__ = {
...window.__BUZZ_E2E__,
mock: { ...window.__BUZZ_E2E__?.mock, channelWindowDelayMs: 1_500 },
};
(
window as unknown as { __CHANNEL_WINDOW_INFLIGHT__?: number }
).__CHANNEL_WINDOW_INFLIGHT__ = 0;
});
const inflightCount = () =>
page.evaluate(
() =>
(window as unknown as { __CHANNEL_WINDOW_INFLIGHT__?: number })
.__CHANNEL_WINDOW_INFLIGHT__ ?? 0,
);
const oldestRenderedIndex = () =>
timeline.evaluate((element) => {
let min = Number.POSITIVE_INFINITY;
for (const row of (
element as HTMLDivElement
).querySelectorAll<HTMLElement>("[data-message-id]")) {
const match = row.textContent?.match(/mock older (\d+)/);
if (match) min = Math.min(min, Number(match[1]));
}
return Number.isFinite(min) ? min : null;
});
// Snapshot the oldest rendered older row before firing the delayed page. Some
// cold windows contain only current rows, so `null` is a valid baseline; the
// landing gate below still requires a real older row to appear after fetch.
const oldestBeforeLanding = await oldestRenderedIndex();
// Re-enter the top band so the persistent observer sees a fresh continuation
// gesture even when the cold window initially placed its sentinel there.
await timeline.hover();
await page.mouse.wheel(0, 1_000);
await page.waitForTimeout(100);
for (let attempt = 0; attempt < 40; attempt += 1) {
if ((await inflightCount()) > 0) break;
await page.mouse.wheel(0, -3000);
await page.waitForTimeout(50);
}
expect(await inflightCount()).toBeGreaterThan(0);
// Capture the reading row WHILE the page is still in flight (prepend lands
// ~1.5s later). This is the row the restore must hold.
const anchorBeforeLanding = await getFirstVisibleMessage(page);
expect(anchorBeforeLanding).not.toBeNull();
// Poll until a genuinely older page has landed (inflight back to 0 AND a new
// older index appeared), then assert the anchored row barely moved. With the
// bug, the prepend lands above the row and shoves it down by the prepend
// height (hundreds of px); with the fix it stays under the first-pass
// content-visibility settle budget.
await expect
.poll(
async () => {
const [inflight, oldestNow, anchor] = await Promise.all([
inflightCount(),
oldestRenderedIndex(),
getMessagePosition(page, anchorBeforeLanding?.id ?? ""),
]);
const landed =
inflight === 0 &&
oldestNow !== null &&
(oldestBeforeLanding === null || oldestNow < oldestBeforeLanding);
if (!landed || !anchor) {
return Number.POSITIVE_INFINITY;
}
return Math.abs(anchor.top - (anchorBeforeLanding?.top ?? 0));
},
{ timeout: 8_000 },
)
.toBeLessThanOrEqual(CHANNEL_HISTORY_PREPEND_SETTLE_PX);
await expect(page.getByTestId("message-scroll-to-latest")).toContainText(
"Jump to latest",
);
});
// Regression: relay-backed thread summaries must remain stable while retained
// rows survive a scrollback prepend.
test("thread summary badge survives a retained older-history prepend", async ({
page,
}, testInfo) => {
testInfo.setTimeout(60_000);
await installMockBridge(page);
await page.goto("/");
await page.waitForFunction(
() => typeof window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__ === "function",
);
// Seed a reply to the NEWEST deep-history row before the channel is opened:
// no live subscription exists yet, so the reply lands only in the mock store.
// It is not a top-level timeline row, so the badge rendered for #599 is
// driven purely by the relay-shaped 39005 page summary — exactly the state
// the deferred-pass entry fallback used to drop.
await page.evaluate(() => {
window.__BUZZ_E2E_EMIT_MOCK_MESSAGE__?.({
channelName: "deep-history",
content: "summary-only reply",
parentEventId: "mock-deep-history-599",
});
});
await page.getByTestId("channel-deep-history").click();
await expect(page.getByTestId("chat-title")).toHaveText("deep-history");
const timeline = page.getByTestId("message-timeline");
const badgeSelector =
'[data-testid="message-thread-summary"][data-thread-head-id="mock-deep-history-599"]';
await expect(timeline.locator(badgeSelector)).toBeVisible();
const oldestRenderedIndex = () =>
timeline.evaluate((element) => {
let min = Number.POSITIVE_INFINITY;
for (const row of (
element as HTMLDivElement
).querySelectorAll<HTMLElement>("[data-message-id]")) {
const match = row.textContent?.match(/#(\d+)/);
if (match) min = Math.min(min, Number(match[1]));
}
return Number.isFinite(min) ? min : null;
});
const oldestBefore = await oldestRenderedIndex();
expect(oldestBefore).not.toBeNull();
// Scroll back until a genuinely older page has landed.
await timeline.hover();
await expect
.poll(
async () => {
await page.mouse.wheel(0, -4000);
await page.waitForTimeout(50);
return oldestRenderedIndex();
},
{ timeout: 20_000 },
)
.toBeLessThan(oldestBefore ?? Number.POSITIVE_INFINITY);
// With `keepMounted`, the summary row intentionally remains available while
// the reader scrolls back. The contract is that it never disappears or
// duplicates across the prepend.
await expect(timeline.locator(badgeSelector)).toBeVisible();
await expect(timeline.locator(badgeSelector)).toHaveCount(1);
});