fix: useInsertionEffect dev warning

[asmyshlyaev177]

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Breaking Changes

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Run ID: 3e3d35ce-d5a8-4b8f-8e6e-7517bb6a94e3

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Reviewing files that changed from the base of the PR and between 9e98504 and abec488.

📒 Files selected for processing (9)

• .gitignore
• packages/example-nextjs16/next-env.d.ts
• packages/urlstate/useIsomorphicLayoutEffect.ts
• packages/urlstate/useSharedState/useSharedState.test.ts
• packages/urlstate/useSharedState/useSharedState.ts
• packages/urlstate/useUrlStateBase/useUrlStateBase.test.ts
• packages/urlstate/useUrlStateBase/useUrlStateBase.ts
• packages/urlstate/utils.test.ts
• packages/urlstate/utils.ts

💤 Files with no reviewable changes (1)

• packages/example-nextjs16/next-env.d.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• .gitignore

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📝 Walkthrough

Walkthrough

The URL state package now defers history listener callbacks to a microtask, uses useIsomorphicLayoutEffect for subscription and navigation handling, adds timing and reconciliation tests, and ignores generated Next.js declaration files.

Changes

URL state timing updates

Layer / File(s)	Summary
Deferred URL notifications packages/urlstate/utils.ts, packages/urlstate/utils.test.ts	subscribeToUrl now invokes history listeners asynchronously after pushState and replaceState. Tests cover callback timing and unsubscribe behavior.
Isomorphic hook subscriptions packages/urlstate/useIsomorphicLayoutEffect.ts, packages/urlstate/useSharedState/..., packages/urlstate/useUrlStateBase/useUrlStateBase.ts, packages/urlstate/useSharedState/useSharedState.test.ts	useSharedState and useUrlStateBase use useIsomorphicLayoutEffect. Tests cover updates between render and subscription, effect ordering, and pre-registration URL changes.
Generated declaration handling .gitignore, packages/example-nextjs16/next-env.d.ts	The generated next-env.d.ts file is removed from the example package and ignored at the repository root.

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

Merge Risk: 🟡 Moderate · up to abec4

The state-synchronization change can briefly display stale external data before reconciliation, and a new test may leave browser history or subscriptions behind after a failure. These bounded issues should be fixed or explicitly accepted before merging.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 7 files. (1 skipped: 1 unsupported.)	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	The description contains only template text and does not explain the proposed changes.	Replace the empty Proposed Changes section with a concise summary of the useInsertionEffect warning fix and related hook updates.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the main change: fixing a development warning related to useInsertionEffect.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch useInsertionEffect_warning

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Actionable comments posted: 2

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Inline comments:
In `@packages/urlstate/useSharedState/useSharedState.ts`:
- Line 67: Replace the useEffect-based synchronization in useSharedState with
useSyncExternalStore or its React 17-compatible shim, using an SSR-safe
pre-paint subscription that reconciles the current URL when registering. Update
useUrlStateBase so popstate changes cannot be missed before listener
registration, and add regression tests covering both stale pre-paint state and
the registration timing window. Affected sites:
packages/urlstate/useSharedState/useSharedState.ts:67-67 requires the
subscription change; packages/urlstate/useUrlStateBase/useUrlStateBase.ts:80-80
requires the corresponding URL reconciliation/listener update.

In `@packages/urlstate/utils.test.ts`:
- Around line 395-416: Update the subscribeToUrl test to capture the initial
window.location.href and wrap its history and assertion flow in try/finally; in
the finally block, always call unsubscribe and restore the captured URL so
cleanup runs even when an assertion fails.

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Fix all unresolved CodeRabbit comments on this PR:

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• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: c61bbea6-dc0d-41c2-a853-fdd9609cbd2e

📥 Commits

Reviewing files that changed from the base of the PR and between ed2c6a1 and 9e98504.

📒 Files selected for processing (6)

• .gitignore
• packages/urlstate/useInsertionEffect.ts
• packages/urlstate/useSharedState/useSharedState.ts
• packages/urlstate/useUrlStateBase/useUrlStateBase.ts
• packages/urlstate/utils.test.ts
• packages/urlstate/utils.ts

💤 Files with no reviewable changes (1)

• packages/urlstate/useInsertionEffect.ts

Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review.