[POC] [WIP] Onyx.get

config/eslint/eslint.config.mjs

@@ -335,6 +335,11 @@ const config = defineConfig([
             'rulesdir/require-live-region-for-status-updates': 'error',
             'rulesdir/require-a11y-disable-justification': 'error',
             'rulesdir/no-direct-pre-insert-fullscreen-under-rhp': 'error',
+            // Position and order for the synchronous Onyx read: not during render, where the read does not subscribe; not at module
+            // scope, where it runs at import time, before Onyx.init() has hydrated the cache; and not after an un-awaited write in
+            // the same body, where Onyx.merge() and Onyx.update() apply in a later microtask so the read returns the pre-write value.
+            // Ships as a warning while the synchronous read is still being introduced; promoted to an error once the first wave of conversions lands.
+            'rulesdir/no-unsafe-onyx-read': 'warn',
             'rulesdir/require-locale-for-localized-date-format': 'error',
             'rulesdir/prefer-narrow-hook-dependencies': [
                 'error',

package.json

@@ -199,7 +199,7 @@
     "react-native-nitro-fetch": "1.5.4",
     "react-native-nitro-modules": "0.36.3",
     "react-native-nitro-sqlite": "9.6.0",
-    "react-native-onyx": "3.0.95",
+    "react-native-onyx": "git+https://github.com/Expensify/react-native-onyx#073821fb322df72f43a6510575f8b1abd93af2e9",
     "react-native-pager-view": "8.0.0",
     "react-native-pdf": "7.0.2",
     "react-native-permissions": "^5.4.0",

scripts/README-onyx-analysis.md

@@ -0,0 +1,88 @@
+# Onyx subscription analysis tooling
+
+Three scripts behind the figures in the `Onyx.get()` proposal. They answer three different
+questions and are independent of each other.
+
+| Script | Question it answers |
+| --- | --- |
+| `analyzeOnyxSubscriptions.ts` | Which `useOnyx` bindings are never read during render, and which `Onyx.connect`/`connectWithoutView` callbacks are nothing but module-level caches |
+| `instrumentOnyxCounters.mjs` | What Onyx actually notified during a recorded interaction, and when |
+| `renderCensus.mjs` | How many renders in a session are components re-rendering for Onyx data they never display |
+
+Nothing here is wired into CI. They are analysis tools, run on demand.
+
+## analyzeOnyxSubscriptions.ts
+
+```bash
+bun scripts/analyzeOnyxSubscriptions.ts                       # summary + candidate tiers
+bun scripts/analyzeOnyxSubscriptions.ts --connect             # Onyx.connect vs connectWithoutView
+bun scripts/analyzeOnyxSubscriptions.ts --provenance <sha>    # migrated legacy vs net-new
+bun scripts/analyzeOnyxSubscriptions.ts --json                # per-binding data, feeds renderCensus
+bun scripts/analyzeOnyxSubscriptions.ts --file <path>         # one file, per-binding verdict
+bun scripts/analyzeOnyxSubscriptions.ts --src /other/App/src  # analyse a different checkout
+```
+
+Purely syntactic — each file is parsed alone, with no type-checker. References resolve by name
+within the declaring function rather than through the symbol table, so a shadowed name is
+over-counted as a reference. That biases a binding toward `render`, which is the safe direction:
+**the non-render set is a lower bound.**
+
+**Run `--provenance` from the repo root, without `--src`.** It compares a `git ls-tree` of the
+baseline against the current working tree, and git returns repo-relative paths. An absolute
+`--src` silently reports 100% net-new because nothing matches.
+
+A binding counts as *non-render* when no reference to it is reachable during render: every
+reference sits behind a function boundary that is not a `useMemo` callback, and none appears in
+JSX. IIFEs and synchronous array callbacks (`map`, `filter`, `reduce`, …) are treated as
+transparent, because they run where they are written — an earlier version got this wrong and
+mis-classified 99 bindings as non-render.
+
+## instrumentOnyxCounters.mjs
+
+Installs notification counters and a timeline into the installed copy of `react-native-onyx`.
+
+```bash
+node scripts/instrumentOnyxCounters.mjs .              # install
+node scripts/instrumentOnyxCounters.mjs --status .     # check
+node scripts/instrumentOnyxCounters.mjs --uninstall .  # remove, byte-for-byte
+```
+
+Then restart the dev server — the bundler caches `node_modules`, so a running server serves the
+uninstrumented build. On load the console prints `[onyxStats] installed`. In the app:
+
+```js
+__onyxStats.reset()      // immediately after clicking Record in the profiler
+__onyxStats.timeline()   // every notification in fire order, ms since reset
+__onyxStats.gaps()       // pauses >= 100ms, where a separate React commit becomes likely
+__onyxStats.json()       // blob for offline comparison
+```
+
+**Edits `node_modules` in place.** Uninstall before regenerating any Onyx patch, or the counters
+get baked into it. Hooks attach only at the top of `keyChanged` and `keysChanged`, whose
+signatures are identical in patched and unpatched builds, so the same instrumentation applies to
+both sides of an A/B and cannot introduce a difference of its own.
+
+**Reset immediately after starting the profiler.** React's timestamps start at profiling start and
+`__onyxStats` starts at `reset()`; if they are seconds apart, matching a notification to the commit
+it caused becomes guesswork.
+
+## renderCensus.mjs
+
+```bash
+bun scripts/analyzeOnyxSubscriptions.ts --json > /tmp/analysis.json
+node scripts/renderCensus.mjs --classifier /tmp/analysis.json <profile.json>
+```
+
+Takes a React DevTools profile export and counts renders that are provably wasted: a hooks-only
+render of a file where *every* `useOnyx` binding is non-render. Requires **"Record why each
+component rendered"** enabled in the profiler, otherwise there is nothing to attribute.
+
+Deliberately a lower bound. Mixed files are excluded rather than guessed at, because
+`changeDescriptions` reports hook indices across all hooks and custom-hook flattening makes
+index-to-binding mapping unreliable. Hook files are excluded too, since a hook's subscriptions
+surface under whichever component called it.
+
+Two things it has to do that are easy to miss: `snapshots` holds only the tree as it stood when
+recording began, so components mounted later are read out of the `operations` log instead
+(skipping this drops name resolution to ~26%), and React Compiler wraps display names as
+`Forget(X)`, which are unwrapped before matching.