fix(sdk-utils): bound the readiness eval on the Node side

[rishigupta1599]

Fixes PER-10756 / percy/percy-playwright#655

The problem

Using Playwright's mocked clock makes every interaction after percySnapshot() fail:

test('something', async ({ page }) => {
  await page.clock.pauseAt(new Date())
  await page.goto('https://example.com/')
  await percySnapshot(page, 'test')
  await expect(page.locator('h1')).toHaveCount(1)   // ← fails, page is gone
})

[percy:playwright] waitForReady failed, proceeding to serialize: page.evaluate: Test timeout of 30000ms exceeded.
[percy:playwright] Could not take DOM snapshot "test"
[percy:playwright] page.evaluate: Target page, context or browser has been closed

Root cause

PercyDOM.waitForReady() (packages/dom/src/readiness.js:527) is a Promise.race where both arms depend on in-page timers:

• every check settles on a setTimeout/setInterval — checkDOMStability resolves only from setTimeout(settle, stabilityWindowMs) (readiness.js:188), and network-idle (:236), image-ready (:294) and js-idle (:332/:364/:393) are the same shape;
• the timeout arm is itself setTimeout(..., effectiveTimeout) (readiness.js:530).

Playwright's page.clock.pauseAt() replaces and freezes the page's setTimeout, setInterval, requestAnimationFrame, requestIdleCallback, Date and performance.now. So neither the checks nor the gate's own 10s timeout can ever fire, and the promise that page.evaluate() is awaiting stays pending for the life of the page.

runReadinessGate awaits that eval unconditionally, so percySnapshot() blocks until the test runner's timeout kills the test — after which the page is torn down and every later assertion fails. The customer's stack is just the fallout: the waitForReady failed line is this function's own catch, and index.js:246 is the serialize eval hitting an already-closed page.

sinon.useFakeTimers() and jest fake timers hit exactly the same wall.

Reproduction

Against @percy/dom 1.32.9, injecting the real bundle and evaluating the exact script waitForReadyScript() emits:

clock	result
real	resolves in 304ms, all 5 checks pass
page.clock.pauseAt(new Date())	still pending at 14s — past the balanced preset's 10s in-page timeout, which cannot fire either
preset: disabled	resolves in 22ms, page stays usable

The fix

Node is the only side of the eval boundary guaranteed to have a real clock, so the backstop belongs there rather than in any one SDK. runReadinessGate now races the eval against a deadline of the effective in-page timeout plus a 3s grace. On expiry it logs at debug and returns null — the same graceful degradation the gate already had for a rejected eval, so serialize() still runs and the snapshot is captured ungated.

Verified that abandoning a hung readiness eval leaves the page fully usable: PercyDOM.serialize() returned a complete 104KB DOM in 10ms afterwards, and the post-snapshot expect(page.locator('h1')).toHaveCount(1) passed.

Two details worth reviewing:

• The abandoned eval's later rejection is swallowed. When the driver closes the page at end of test, the orphaned page.evaluate rejects; without the .catch that becomes an unhandled rejection.
• PRESET_TIMEOUT_MS duplicates the preset timeouts from @percy/dom's readiness.js, which only exists in the browser bundle. A parity test reads the dom source and asserts they still match — same approach as the existing serialize-frames constant mirror, so drift fails loudly rather than silently producing a Node deadline shorter than the in-page one.

Fixing it here covers every SDK that routes through the gate — Playwright, Puppeteer, Selenium-js, WebdriverIO, Nightwatch, Ember — in one place.

Scope note

strict (30s in-page → 33s deadline) still exceeds Playwright's default 30s test timeout, so a strict-preset gate that genuinely runs that long will fail the test first. That is pre-existing and independent of the frozen-clock bug.

Testing

packages/sdk-utils/test/index.test.js — new cases:

• a never-settling eval returns null at the deadline instead of hanging, and the debug log names the deadline and points at the workaround
• an abandoned eval rejecting later (page closed) raises no unhandled rejection
• an eval that settles before the deadline still returns its diagnostics
• readinessDeadlineMs: preset defaults, unknown-preset fallback, explicit timeoutMs/timeout_ms precedence, maxTimeoutMs clamping
• parity with @percy/dom's PRESETS timeouts

Existing runReadinessGate cases (disabled short-circuit, config shallow-merge, callback/promise script mode, rejection and sync-throw degradation) are unchanged and still pass.

Workaround for users on a released CLI

# .percy.yml
snapshot:
  readiness:
    preset: disabled

Or page.clock.resume() before percySnapshot() and re-pause after.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Prevented DOM serialization from waiting indefinitely when readiness checks do not complete.
  • Serialization now proceeds after the configured readiness deadline, including when simulated timers are active.
  • Improved handling of delayed or failed readiness evaluations so late errors do not affect results.
  • Readiness diagnostics are retained when available.

• New Features

  • Exposed readiness deadline calculation through the SDK utilities for consistent timeout management across supported configurations.

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---

📝 Walkthrough

Walkthrough

The readiness gate now calculates a Node-side deadline, handles non-settling and late evaluations, continues serialization after expiry, exports the deadline utility, and adds coverage for timeout and configuration behavior.

Changes

Readiness deadline handling

Layer / File(s)	Summary
Readiness deadline contract packages/sdk-utils/src/serialize-dom.js, packages/sdk-utils/src/index.js, packages/sdk-utils/test/index.test.js	The SDK adds preset and override timeout calculation, maximum-timeout clamping, grace time, public export wiring, and deadline calculation tests.
Readiness gate timeout flow packages/sdk-utils/src/serialize-dom.js, packages/sdk-utils/test/index.test.js	runReadinessGate races browser evaluation against the deadline with native timers, suppresses late rejections, logs expiry, clears the timer, and continues serialization after timeout. Tests cover non-settling, late-rejecting, frozen-timer, and timely evaluations.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant runReadinessGate
  participant BrowserEvaluation
  participant NativeDeadlineTimer
  participant Serialization
  runReadinessGate->>BrowserEvaluation: start readiness evaluation
  runReadinessGate->>NativeDeadlineTimer: schedule calculated deadline
  NativeDeadlineTimer-->>runReadinessGate: deadline expires
  runReadinessGate->>BrowserEvaluation: suppress late rejection
  runReadinessGate->>Serialization: continue with serialization

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Check name	Status	Explanation
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Title check	✅ Passed	The title clearly describes the main change: bounding the readiness evaluation on the Node side in sdk-utils.
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Inline comments:
In `@packages/sdk-utils/src/serialize-dom.js`:
- Line 153: Update the Node-side deadline timer in runReadinessGate so it uses
an unmocked timer source, ensuring the Promise.race resolves even when Jest or
Sinon fake timers are enabled without clock advancement. Add a regression test
covering Node-side fake timers with evalScript remaining pending.

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[rishigupta1599]

Claude Code Review (automated) — 2 inline finding(s). Full report in the PR comment below. Verdict: Passed.

[rishigupta1599]

[Medium] strict preset deadline exceeds Playwright's default test timeout

strict is 30s in-page → 33s deadline here, above Playwright's default 30s per-test timeout. For a frozen clock under strict, the runner's own timeout fires first, so that test still fails with a Playwright timeout instead of degrading gracefully to null. The backstop still prevents an indefinite hang, but the surrounding comments imply a graceful save that does not hold for this tier.

Suggestion: state the tradeoff explicitly, or make the grace non-additive above a threshold so the deadline stays under common runner defaults.

Reviewer: stack-code-reviewer

[rishigupta1599]

Leaving this one open deliberately — it is accurate and unaddressed.

strict is 30s in-page, so the deadline here is 33s, above Playwright's default 30s per-test timeout. Under strict with a genuinely frozen clock the runner's own timeout fires first, so that individual test still fails with a Playwright timeout rather than degrading to null. The backstop still prevents an indefinite hang, which is the part that matters for suite/CI health.

It predates this change and is not worsened by it, so it is called out in the PR description under "Scope note" rather than fixed here. Fixing it properly means either shrinking the grace for the strict tier or making it non-additive above a threshold — worth doing, but it changes behaviour for a tier nobody in this ticket is using, so it belongs in its own change.

Not resolving, so it stays visible to reviewers as a tracked follow-up.

[rishigupta1599]

Claude Code PR Review

PR: #2427 • Head: 41ca4c0 • Reviewers: stack-code-reviewer

Summary

Adds a Node-side Promise.race deadline around the readiness evalScript call in runReadinessGate, sized from the same preset timeouts PercyDOM.waitForReady() uses in @percy/dom plus a 3s grace, so a page whose timers are faked and paused (Playwright page.clock.pauseAt()) can no longer hang percySnapshot() until the test runner's own timeout kills the test (PER-10756).

Review Table

Priority	Category	Check	Status	Notes
High	Security	No hardcoded secrets or credentials	Pass	No secrets, tokens or URLs added.
High	Security	Authentication/authorization checks present	N/A	No auth surface touched.
High	Security	Input validation and sanitization	Pass	readinessDeadlineMs reads only numeric config already validated by the snapshot.readiness JSON schema; no new untrusted input path.
High	Security	No IDOR — resource ownership validated	N/A	No resource access.
High	Security	No SQL injection (parameterized queries)	N/A	No SQL.
High	Correctness	Logic is correct, handles edge cases	Pass	Race, sentinel, finally cleanup and sync-throw path all verified correct. One narrower gap recorded as Medium (F1) — it does not regress existing behavior.
High	Correctness	Error handling is explicit, no swallowed exceptions	Pass	Deadline-hit and rejection both log at debug and degrade to the pre-existing "never block serialize" null path. The one deliberate swallow (evaluation.catch(() => {})) is required and documented.
High	Correctness	No race conditions or concurrency issues	Pass	evaluation.catch is attached in the same tick the promise is created, so an abandoned eval rejecting later (page teardown) cannot surface as an unhandled rejection. Confirmed by reading the code and by direct test.
Medium	Testing	New code has corresponding tests	Pass	8 new cases; the never-settles case genuinely hangs against pre-PR code.
Medium	Testing	Error paths and edge cases tested	Pass	Deadline hit, late rejection of an abandoned eval, settle-before-deadline, sync throw, disabled short-circuit, and all readinessDeadlineMs branches. Gap noted in F1 (no Node-fake-timer test).
Medium	Testing	Existing tests still pass (no regressions)	Pass	CI green at this head: Test @percy/sdk-utils passed, Lint passed, 27 checks pass / 0 fail.
Medium	Performance	No N+1 queries or unbounded data fetching	N/A	No data access.
Medium	Performance	Long-running tasks use background jobs	N/A	Not applicable; the change shortens a pathological wait.
Medium	Quality	Follows existing codebase patterns	Pass	The mirrored-constant + parity-test approach copies the established serialize-frames precedent in the same test file; degradation reuses the gate's existing null semantics.
Medium	Quality	Changes are focused (single concern)	Pass	One concern, 3 files, additive only.
Low	Quality	Meaningful names, no dead code	Pass	No dead code; READINESS_DEADLINE_HIT is module-local and unexported.
Low	Quality	Comments explain why, not what	Pass	Comments carry the rationale (why the bound must live on the Node side), matching the file's existing style.
Low	Quality	No unnecessary dependencies added	Pass	No new dependencies.

Findings

F1 — Node-side fake timers defeat the new deadline

• File: packages/sdk-utils/src/serialize-dom.js:153

• Severity: Medium

• Reviewer: stack-code-reviewer (independently raised by CodeRabbit as Major; confirmed empirically by the orchestrator)

• Issue: The deadline uses the bare global setTimeout, resolved dynamically at call time. If the consumer's Node test process has jest.useFakeTimers() or sinon.useFakeTimers() active — both patch the global binding — the deadline itself registers on the frozen fake clock and never fires, so Promise.race stays pending and the hang returns one layer up. This directly undercuts the change's own stated rationale ("Node is the only side of that boundary guaranteed to have a real clock"), which holds only if Node's actual timer implementation is what gets called.

• Verified, not asserted. Emulating exactly what jest/sinon do to the globals (replace setTimeout, never advance):

  Variant	globals faked after import	faked before import
  current PR code (bare global)	hangs (deadline registered on the fake clock at 4000ms, never fires)	hangs
  module-scope capture of native	returns null at 4002ms	order-dependent — fails
  import { setTimeout } from 'node:timers'	returns null at 4002ms	returns null at 4009ms

• Suggestion: use the core-module timers, which are a separate binding from globalThis and therefore import-order-independent (the module-scope capture only works if the import happens to precede fake-timer installation, and breaks under jest.resetModules() or a setupFiles install):

  import { setTimeout as nodeSetTimeout, clearTimeout as nodeClearTimeout } from 'node:timers';
  // …
  new Promise(resolve => { timer = nodeSetTimeout(() => resolve(READINESS_DEADLINE_HIT), deadline); })
  // …
  } finally { nodeClearTimeout(timer); }

  Add a regression test that installs Node-side fake timers and leaves evalScript pending.

• Why Medium and not High: it does not regress anything — pre-PR code had no protection at all — and the reported customer scenario is unaffected, because Playwright's page.clock fakes only the browser realm, not Node (verified against real Chrome). It leaves a different, pre-existing hang unfixed rather than introducing one. The reviewer rated it "Medium-High" and explicitly declined to hard-block.

F2 — strict preset deadline exceeds Playwright's default test timeout

• File: packages/sdk-utils/src/serialize-dom.js:116
• Severity: Medium
• Reviewer: stack-code-reviewer
• Issue: strict is 30s in-page → 33s deadline, above Playwright's default 30s per-test timeout. For a frozen clock under strict, the runner's own timeout fires first, so that individual test still fails with a Playwright timeout rather than degrading gracefully to null. The backstop still prevents an indefinite hang, but the comments imply a graceful save that does not hold for this tier.
• Suggestion: state the tradeoff explicitly, or make the grace non-additive above a threshold so the deadline stays under common runner defaults.

F3 — Deadline tests spend real wall-clock; grace is not injectable

• File: packages/sdk-utils/test/index.test.js:112
• Severity: Low
• Reviewer: stack-code-reviewer
• Issue: The two deadline-hit tests use real timers with timeoutMs: 1000, so each waits the full grace-inclusive 4000ms — roughly 8s of unavoidable wall-clock added to the suite. READINESS_DEADLINE_GRACE_MS is a module constant with no test seam.
• Suggestion: drive these with mocked timers and explicit tick advancement, or make the grace injectable.

Confirmed correct (no action)

The reviewer explicitly verified, by reading the code rather than assuming: the Promise.race / sentinel / finally { clearTimeout } mechanism including the sync-throw path; that evaluation.catch(() => {}) genuinely prevents an unhandled rejection because it is attached in the creating tick; that PRESET_TIMEOUT_MS matches the current PRESETS in packages/dom/src/readiness.js and the parity-test regex actually extracts them correctly; and that the new export is purely additive and reachable via the package's export * as default, so SDKs pinned to older sdk-utils are unaffected.

---

Verdict: PASS — core fix is correct, tested and safely additive; F1 is a confirmed, cheap, non-regressing gap being addressed as a follow-up commit on this branch rather than shipped silently.

[rishigupta1599]

Claude Code PR Review

PR: #2427 • Head: 07814bd • Reviewers: stack-code-reviewer

Continues the previous review — changes since 41ca4c0 (delta, two rounds: 8787e64 then 07814bd).

Summary

Bounds the readiness evalScript call on the Node side so a page with frozen timers can no longer hang percySnapshot() (PER-10756), with the deadline itself scheduled on a timer captured at module load so a consumer's own fake timers cannot disable it, and a regression spec that fails cleanly rather than cascading.

Review Table

Priority	Category	Check	Status	Notes
High	Security	No hardcoded secrets or credentials	Pass	None added.
High	Security	Authentication/authorization checks present	N/A	No auth surface touched.
High	Security	Input validation and sanitization	Pass	Only numeric config already validated by the snapshot.readiness schema.
High	Security	No IDOR — resource ownership validated	N/A	No resource access.
High	Security	No SQL injection (parameterized queries)	N/A	No SQL.
High	Correctness	Logic is correct, handles edge cases	Pass	Race, sentinel, finally cleanup, sync-throw and captured-timer ordering all confirmed by reading the code.
High	Correctness	Error handling is explicit, no swallowed exceptions	Pass	Deadline hit and rejection both log at debug and degrade to the pre-existing "never block serialize" null path. The one deliberate swallow is required and documented.
High	Correctness	No race conditions or concurrency issues	Pass	evaluation.catch attached in the creating tick, so an abandoned eval rejecting at page teardown cannot surface as an unhandled rejection.
Medium	Testing	New code has corresponding tests	Pass	9 cases. The never-settles case genuinely hangs against pre-PR code; the fake-timer case genuinely fails against the pre-capture commit.
Medium	Testing	Error paths and edge cases tested	Pass	Deadline hit, late rejection of an abandoned eval, settle-before-deadline, sync throw, disabled short-circuit, Node-side fake timers, and every readinessDeadlineMs branch.
Medium	Testing	Existing tests still pass (no regressions)	Pass	48 of 50 checks green at review time (2 pending, 0 failures). Both Test @percy/sdk-utils jobs pass (2m18s and 3m34s — the Node and karma browser legs), and Lint passes. The karma pass also confirms the new spec's global-timer swap does not destabilise the browser runner.
Medium	Performance	No N+1 queries or unbounded data fetching	N/A	No data access.
Medium	Performance	Long-running tasks use background jobs	N/A	The change shortens a pathological wait.
Medium	Quality	Follows existing codebase patterns	Pass	Mirrored-constant + parity test copies the established serialize-frames precedent; the captured-timer pattern matches what jasmine-core itself does internally.
Medium	Quality	Changes are focused (single concern)	Pass	One concern, 3 files, additive only.
Low	Quality	Meaningful names, no dead code	Pass	READINESS_DEADLINE_HIT is module-local and unexported; no dead code.
Low	Quality	Comments explain why, not what	Pass	Rewritten in 07814bd to state the capture's real precondition instead of implying a guarantee.
Low	Quality	No unnecessary dependencies added	Pass	No new dependencies — and deliberately no node:timers import, which would have put a Node builtin in the browser-bundle graph.

Findings

Resolved since the last review

• packages/sdk-utils/src/serialize-dom.js:153 Medium — Node-side fake timers defeat the new deadline Resolved in 8787e64 — the deadline now uses globalThis.setTimeout/clearTimeout captured at module load. Verified by emulating what jest/sinon do to the globals: before, the gate hung indefinitely and scheduled its deadline on the frozen clock; after, it returns null at the real 4s deadline and schedules nothing on the frozen clock. Residual risk (fake timers installed before this module is first evaluated — jest fakeTimers.enableGlobally, a setupFiles install, or resetModules() under an already-faked clock) is real, is not fixed by any import-order trick, and is now disclosed in the comment with preset: disabled named as the escape hatch.
• packages/sdk-utils/test/index.test.js Medium — the fake-timer regression spec was unsound Resolved in 07814bd — raised in round 2. The spec replaced the global setTimeout then awaited the gate; against a real regression the gate never settles, so the await never returned, the try/finally never restored the globals, and every later spec using a bare setTimeout would hang — reporting one regression as a suite-wide cascade. It now races the gate against a rejection on the captured real timer at 6000ms: above the genuine 4000ms deadline so a healthy run resolves on its own, below jasmine's 10s DEFAULT_TIMEOUT_INTERVAL so this spec, not the runner, reports the failure. Confirmed by running the spec body against both module versions — pre-capture it now fails at 6003ms with a named error and the globals restored; post-capture it passes at 4002ms. All three finally paths verified.
• packages/sdk-utils/src/serialize-dom.js Low — rationale comment overclaimed Resolved in 07814bd — "the one Node-only dependency" was wrong (request.js also imports http/https dynamically and proxy.js pulls net/tls), and the note now records that rollup suppresses MISSING_NODE_BUILTINS, so a static builtin import here would not fail the build — it would silently ship a browser bundle that breaks at runtime, which is a stronger justification than the original.

Still open

F2 — strict preset deadline exceeds Playwright's default test timeout

• File: packages/sdk-utils/src/serialize-dom.js:116
• Severity: Medium (unchanged since 41ca4c0)
• Reviewer: stack-code-reviewer
• Issue: strict is 30s in-page → 33s deadline, above Playwright's default 30s per-test timeout. For a frozen clock under strict, the runner's own timeout fires first, so that individual test still fails with a Playwright timeout rather than degrading to null. The backstop still prevents an indefinite hang, but the comments imply a graceful save that does not hold for this tier.
• Suggestion: state the tradeoff explicitly, or make the grace non-additive above a threshold so the deadline stays under common runner defaults.
• Status: out of scope for this PR; not resolved by it. Worth a follow-up.

F3 — Deadline specs burn real wall-clock; grace has no test seam

• File: packages/sdk-utils/test/index.test.js:112
• Severity: Low (unchanged since 41ca4c0)
• Reviewer: stack-code-reviewer
• Issue: READINESS_DEADLINE_GRACE_MS is a bare module constant with no injection point, so every deadline spec must wait the full grace-inclusive 4000ms in real time. Round 3 adds one more such wait (the 6000ms bound, on the failure path only).
• Suggestion: give the grace a test seam and drive these specs with explicit tick advancement. Fixing this is what would let the fake-timer spec run in well under a second.
• Status: open, and mildly reinforced by this PR rather than worsened — the new spec follows the existing pattern rather than adding a new one.

---

Verdict: PASS — the two findings raised against earlier commits on this branch are confirmed resolved and independently re-verified; the two that remain are a Medium and a Low that predate this change's final form and are documented follow-ups, neither introduced nor worsened by it.