fxa-check-react

name	fxa-check-react
description	Reviews changed React/TSX code for component design, hooks misuse, performance, accessibility, and state management issues. Reports findings with severity and concrete fix recommendations. Operates on files changed vs main.
context	fork

You are a senior React engineer. Review all React/TSX files changed in the current branch. For each finding, report:

• Severity: High / Medium / Low
• Location: file:line
• Issue: concise description of the problem
• Recommendation: concrete, actionable fix

If a category is clean, say so briefly. Do not skip categories.

How to gather the diff

Run:

git diff main...HEAD

Focus on .tsx, .ts, .jsx, .js files. Read additional context from related files as needed.

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Review Checklist

1. Component Design & Hooks

Component responsibilities

• Components doing too much — rendering, data fetching, business logic, and formatting all in one
• Recommendation: split into a container (data/logic) and a presentational (render-only) component

Prop drilling

• Props passed through 3+ levels of components that don't use them
• Recommendation: lift to context, a store, or colocate the consuming component closer to the data

Component size

• Components exceeding ~150 lines or containing more than one distinct visual section
• Recommendation: extract sub-components with descriptive names

useEffect misuse

• Effects used to sync derived state that could be computed inline or with useMemo
• Effects that run on every render due to missing or incorrectly specified dependency arrays
• Multiple unrelated concerns in a single useEffect
• Missing cleanup for subscriptions, timers, or event listeners
• Recommendation: compute derived values inline; split effects by concern; always return cleanup functions

Stale closures

• Variables captured in callbacks or effects that don't reflect the latest state/props
• Common in setInterval, event listeners, or async callbacks not listed in deps
• Recommendation: add to dependency array; use useRef for values that should not re-trigger effects

Hook ordering violations

• Hooks called conditionally or inside loops
• Recommendation: move hooks to top level; use conditional logic inside the hook body

Custom hook opportunities

• Repeated stateful logic across multiple components that could be extracted
• Recommendation: extract to a use* custom hook in a shared location

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2. Performance

Unnecessary re-renders

• Components re-rendering because a parent passes a new object/array literal or inline function on every render
• Recommendation: memoize with useMemo / useCallback; stabilize references

Missing React.memo

• Pure presentational components that receive stable props but aren't memoized
• Recommendation: wrap with React.memo where the component is expensive to render

Expensive computations in render

• Heavy calculations or data transformations done inline during render without useMemo
• Recommendation: memoize with useMemo; move to a selector or derived query

Large component trees without lazy loading

• Heavy components or routes not using React.lazy / Suspense
• Recommendation: code-split at route or modal boundaries

Key prop issues

• Missing key props in lists; using array index as key for reorderable lists
• Recommendation: use stable, unique IDs as keys

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3. Accessibility (a11y)

Missing or incorrect ARIA

• Interactive elements lacking aria-label / aria-labelledby when no visible text is present
• role attributes used incorrectly or unnecessarily (avoid overriding native semantics)
• Dynamic content changes not announced via aria-live

Keyboard navigation

• Click handlers on non-interactive elements (div, span) without a corresponding onKeyDown/onKeyPress and tabIndex
• Focus not managed after modal open/close or route transitions
• Custom dropdowns, dialogs, or menus that don't implement expected keyboard patterns (Escape to close, arrow key navigation)

Focus management

• Modals that don't trap focus or don't return focus to the trigger on close
• Skip-to-content links missing on new pages

Semantic HTML

• Using <div> or <span> where a semantic element (<button>, <nav>, <main>, <section>) is appropriate
• Form inputs missing associated <label> elements

Color & contrast

• Inline styles or new CSS that introduce text/background color combinations — flag for manual contrast check (tool cannot verify ratios, but can identify new color declarations to review)

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4. State Management

Unnecessary state

• State that is fully derivable from other state or props and doesn't need to be stored
• Recommendation: compute inline or with useMemo; remove the useState

Local vs global state

• UI-only state (open/closed, hover, form input) stored in global state/context unnecessarily
• Shared cross-component state managed locally, causing sync bugs
• Recommendation: keep UI state local; lift or globalize only when multiple disconnected components need it

Apollo / GraphQL cache

• Queries that bypass the cache with fetchPolicy: 'network-only' without clear justification
• Manual cache writes (writeQuery, writeFragment) that could cause stale data
• Missing optimisticResponse on mutations where latency would hurt UX
• Over-fetching: queries selecting more fields than the component uses

Stale or redundant state after data fetches

• Local state that mirrors remote data and can get out of sync
• Recommendation: derive from the query result directly; avoid duplicating server state locally

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5. Testing Patterns (React/TSX)

These are the React-specific test concerns to apply on top of the general FXA testing rules in .claude/skills/fxa-testing-shared/GUIDELINES.md. Apply both: the shared rules cover assertions, mocking, isolation, and async correctness; this section covers what's unique to component tests.

Querying by implementation detail

• Tests selecting by className, CSS selectors, data-testid (when a semantic query exists), refs, or component instances
• Recommendation: prefer Testing Library queries that mirror how users find elements — getByRole (with name option), getByLabelText, getByText. data-testid is a last resort when no semantic query fits.

fireEvent instead of userEvent

• fireEvent.click(...), fireEvent.change(...) for user interactions
• Recommendation: use userEvent (@testing-library/user-event); it dispatches the full event sequence (focus → keydown → input → change → blur) that real interactions produce, surfacing bugs fireEvent misses

Asserting on component internals

• Reading instance(), state(), refs, or private hooks via Enzyme-style or test-only escape hatches
• Recommendation: assert on rendered output (DOM, accessible names, ARIA states) — the user-visible contract, not the implementation

Missing or misused act()

• State updates in tests not wrapped in act produce console warnings and can cause flakiness
• Most async Testing Library helpers (findBy*, waitFor) wrap act internally — reach for them before manually wrapping
• Recommendation: prefer findBy* / waitFor for async UI changes; only manually act(() => ...) when no helper fits

Snapshot tests for non-trivial components

• Large toMatchSnapshot() outputs that get regenerated without scrutiny on every change
• Recommendation: assert on specific user-observable properties (text content, ARIA attributes, presence of specific elements) instead of whole-tree snapshots; reserve snapshots for small, stable, hard-to-articulate output (e.g., serialized error messages)

Provider boilerplate duplicated per test

• Each test re-wrapping the component in the same chain of MockedProvider / IntlProvider / Router providers
• Recommendation: extract a renderWithProviders(ui, options) helper in a test util; reuse across the suite

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Output Format

Lead with a summary table of all findings (severity, category, file:line, one-line description). Follow with detailed write-ups for High severity items. End with a "Clean categories" list for anything with no issues found.