[WIP][POC] Flip the subscription layer onto OnyxStore (atomic swap) by fabioh8010 · Pull Request #834 · Expensify/react-native-onyx

fabioh8010 · 2026-08-31T12:23:29Z

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I linked the correct issue in the ### Related Issues section above
I linked the corresponding Expensify/App PR in the ### Linked E/App PR section above, and verified this change against it (E/App CI passed and manual testing completed)
I wrote clear testing steps that cover the changes made in this PR
- I added steps for local testing in the Tests section
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- I verified that any callback methods that were added or modified are named for what the method does and never what callback they handle (i.e. toggleReport and not onIconClick)
- I verified that the left part of a conditional rendering a React component is a boolean and NOT a string, e.g. myBool && <MyComponent />.
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- I verified that any new or modified comments were clear, correct English, and explained "why" the code was doing something instead of only explaining "what" the code was doing.
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If a new code pattern is added I verified it was agreed to be used by multiple Expensify engineers
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I tested other components that can be impacted by my changes (i.e. if the PR modifies a shared library or component like Avatar, I verified the components using Avatar are working as expected)
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I verified any variables that can be defined as constants (ie. in CONST.js or at the top of the file that uses the constant) are defined as such
I verified that if a function's arguments changed that all usages have also been updated correctly
If a new component is created I verified that:
- A similar component doesn't exist in the codebase
- All props are defined accurately and each prop has a /** comment above it */
- The file is named correctly
- The component has a clear name that is non-ambiguous and the purpose of the component can be inferred from the name alone
- The only data being stored in the state is data necessary for rendering and nothing else
- If we are not using the full Onyx data that we loaded, I've added the proper selector in order to ensure the component only re-renders when the data it is using changes
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If any new file was added I verified that:
- The file has a description of what it does and/or why is needed at the top of the file if the code is not self explanatory
If the PR modifies a generic component, I tested and verified that those changes do not break usages of that component in the rest of the App (i.e. if a shared library or component like Avatar is modified, I verified that Avatar is working as expected in all cases)
If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.
I have checked off every checkbox in the PR author checklist, including those that don't apply to this PR.

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Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

Introduce lib/OnyxStore.ts: a single listener registry (keyListeners Map<key, Set<listener>>) with subscribe / notifyKey / notifyCollection / getState / hasListenersForKey / clearAll. Built on the existing structural-sharing cache (cache.getCollectionData frozen snapshots). This module is inert — nothing imports it yet. The subscription and notification paths (Onyx.connect, useOnyx, OnyxUtils.notify*) are wired onto it in a later change. Adding it alone has zero behavioral impact. Includes tests/unit/OnyxStoreTest.ts (20 tests) covering exact-key and collection-snapshot routing, ref-equality member skips, hasListenersForKey, clearAll, and listener error isolation. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Wire useOnyx, Onyx.connect/disconnect, and the OnyxUtils notify path onto the OnyxStore registry. useOnyx is rebuilt on useSyncExternalStore reading the eager, structurally-shared cache via onyxStore.getState — it renders once (no loading->loaded second render) and bails out via === on the stable cached reference. Delete OnyxConnectionManager and OnyxSnapshotCache (and their unit + perf tests). Also remove the now-defunct reuseConnection option (connection pooling is gone). The `loading` status value is retained for now (always 'loaded' in practice) and removed in a follow-up; OnyxStore stays trimmed (no subscribeState) since useOnyxState is a separate proposal. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Rebuild the store-based useOnyx on React's useSyncExternalStoreWithSelector (use-sync-external-store/with-selector) with deepEqual as the equality fn. Its committed-value dedup collapses content-equal selections to a stable reference and survives the selector function's identity churning every render — so consumers can pass inline selectors that close over freshly allocated arrays/objects without stabilizing the inputs (no more useStableArrayReference). No-selector subscriptions keep the Object.is fast-path since the raw cache value is already reference-stable. Adds use-sync-external-store + @types/use-sync-external-store. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fabioh8010 · 2026-08-31T12:23:41Z

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chatgpt-codex-connector · 2026-08-31T12:29:09Z

+    const isLoading = connectedKeyRef.current !== key && OnyxUtils.hasPendingMergeForKey(key);
+    const loadingStatus: FetchStatus = isLoading ? 'loading' : 'loaded';


Re-render when the initial pending merge settles

When this hook mounts or switches keys while a no-op merge is pending—for example, merging data already present in the cache—isLoading makes it return [undefined, {status: 'loading'}], but merge completion does not necessarily notify the store because broadcastUpdate() returns when hasChanged is false. The effect only mutates connectedKeyRef without scheduling a render, so the hook can remain permanently blank and loading. The merge-settlement path needs to trigger a render even when the cached snapshot does not change.

Useful? React with 👍 / 👎.

Addressed in 3fd8b91

…ached key

fabioh8010 and others added 8 commits August 18, 2026 15:32

fix: restore loading status for in-flight merges in useOnyx

31fdebd

Merge branch 'main' into feature/onyx-store-pr-5-recut

3be173a

fix: scope useOnyx loading status to a key's first connection

db69973

Simplify comments and remove snapshot wording

11bd40c

Simplify comments

4d023b4

melvin-bot Bot assigned fabioh8010 Aug 31, 2026

chatgpt-codex-connector Bot reviewed Aug 31, 2026

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fabioh8010 added 3 commits September 1, 2026 08:03

Remove dead code

e0a71a4

Simplify comments

bfb0144

Fix useOnyx stuck on loading when a merge is pending for an already-c…

3fd8b91

…ached key

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[WIP][POC] Flip the subscription layer onto OnyxStore (atomic swap) - #834

[WIP][POC] Flip the subscription layer onto OnyxStore (atomic swap)#834
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		const isLoading = connectedKeyRef.current !== key && OnyxUtils.hasPendingMergeForKey(key);
		const loadingStatus: FetchStatus = isLoading ? 'loading' : 'loaded';

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