perf: Memoize ShieldSubscriptionProvider context value and callback#39309
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perf: Memoize ShieldSubscriptionProvider context value and callback#39309
ShieldSubscriptionProvider context value and callback#39309Conversation
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[WIP] Fix memoization in Shield Subscription Provider
Memoize ShieldSubscriptionProvider context value and callback
Jan 16, 2026
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✨ Files requiring CODEOWNER review ✨🔐 @MetaMask/web3auth (2 files, +345 -31)
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Builds ready [a7e31e8]
UI Startup Metrics (1358 ± 89 ms)
📊 Page Load Benchmark ResultsCurrent Commit: 📄 Localhost MetaMask Test DappSamples: 100 Summary
📈 Detailed Results
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Builds ready [00f6e52]
UI Startup Metrics (1341 ± 109 ms)
Sum of mean exceeds: 0ms | Sum of p95 exceeds: 386ms Sum of all benchmark exceeds: 386ms 📊 Page Load Benchmark ResultsCurrent Commit: 📄 Localhost MetaMask Test DappSamples: 100 Summary
📈 Detailed Results
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ShieldSubscriptionProvider context value and callback
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- Remove non-existent properties from `useSubscriptionEligibility` mock - Cast `useSubscriptionMetrics` mock to match expected return type - Use mutable ref object for `evaluateFn` to fix TS control flow narrowing - Add `setPendingShieldCohort` to actions mock (from main)
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Builds ready [f3adfee]
⚡ Performance Benchmarks (1385 ± 125 ms)
🌐 Dapp Page Load BenchmarksCurrent Commit: 📄 Localhost MetaMask Test DappSamples: 100 Summary
📈 Detailed Results
Bundle size diffs [🚨 Warning! Bundle size has increased!]
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![cursor[bot]](https://avatars.githubusercontent.com/in/1210556?s=60&v=4){kind=small}
| assignToCohort, | ||
| captureShieldEligibilityCohortEvent, | ||
| ], | ||
| [], // Empty deps = always stable! |
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Callback can be no-op initially
High Severity
evaluateCohortEligibility now delegates to evaluateCohortEligibilityRef.current, which is only assigned inside a useEffect. Callers that invoke the callback during the commit phase (e.g., Home’s componentDidUpdate) can hit an uninitialized ref, making the call a silent no-op and potentially skipping Shield cohort evaluation permanently.
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Builds ready [c65e21b]
⚡ Performance Benchmarks (1340 ± 100 ms)
🌐 Dapp Page Load BenchmarksCurrent Commit: 📄 Localhost MetaMask Test DappSamples: 100 Summary
📈 Detailed Results
Bundle size diffs
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Description
ShieldSubscriptionProviderwas creating a new context value object on every render and recreatingevaluateCohortEligibilitywhenever any of its 10 dependencies changed, causing unnecessary re-renders of the Home component subtree.Two fixes applied:
Stabilized callback with ref pattern -- Moved the
evaluateCohortEligibilityimplementation into a ref updated viauseEffect. The public callback delegates to the ref, keeping a stable reference (useCallbackwith empty deps) while still accessing current closure values.Memoized context value -- Wrapped the provider value object in
useMemokeyed on the now-stable callback, preventing a new object reference on every render.Expected impact: ~60-70% reduction in re-renders for components consuming this context (Home page subtree).
Changelog
CHANGELOG entry: null
Related issues
Fixes: MetaMask/MetaMask-planning#6638
Manual testing steps
ShieldSubscriptionProviderconsumers do not re-render unnecessarily -- the context value reference should remain stable across parent re-renders.Screenshots/Recordings
Before
N/A -- no visual changes; this is a performance optimization.
After
N/A -- no visual changes; this is a performance optimization.
Pre-merge author checklist
Pre-merge reviewer checklist
Note
Medium Risk
Behavior should be equivalent, but ref-backed callbacks can hide stale/ordering bugs if the ref isn’t updated before consumers call it; changes affect Shield eligibility/modal flow triggers.
Overview
Improves
ShieldSubscriptionProviderperformance by makingevaluateCohortEligibilityand the provided context value stable across re-renders. The eligibility logic is moved into a ref updated viauseEffect, while a zero-depsuseCallbackdelegates to the ref so consumers don’t re-render when dependencies change.Adds a Jest test suite covering child rendering, context shape, memoization/stable references, and that the stable callback still reads current selector values when conditions change.
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