Expo iOS HIG Verifier

A read-only static checker that scans an Expo (React Native) project for violations of the expo-ios-hig rules and reports them grouped by severity, with file:line locations and links to the rule that explains the fix. It is the automated counterpart to the expo-ios-hig reference skill: that skill teaches the rules; this one checks them.

When to Apply

Run this skill when:

The user asks to check, lint, audit, or review an Expo app for HIG compliance or native feel
Before merging or shipping Expo iOS UI changes, as a quality gate
After scaffolding new screens, to confirm they stay native
Investigating why an Expo app "feels like a web wrapper" or "feels like Android"

It is read-only — it never modifies the target project, so it is safe to run unsupervised.

Workflow Overview

verify-hig.sh [project-dir]
  1. Resolve search roots (app/ src/ components/ by default, or config.json)
  2. Run static checks — one per detectable expo-ios-hig rule (rg, or grep fallback)
  3. Aggregate findings: severity, rule, message, file:line
  4. Print grouped report (ERRORS then ADVISORIES) with a link to each rule
  5. Exit 0 if clean, 1 if any ERROR (with --strict, advisories fail too)

Run it:

bash scripts/verify-hig.sh /path/to/expo-app          # text report
bash scripts/verify-hig.sh /path/to/expo-app --strict # advisories also fail
bash scripts/verify-hig.sh /path/to/expo-app --json   # machine-readable

Checks

ERRORS are high-precision (import and literal-flag matches, low false positives). ADVISORIES are heuristics that warrant a look but don't fail the run unless --strict.

Severity	Rule	Detects
ERROR	`native-avoid-material-ui`	`react-native-paper`, `@react-native-material/`, `@rneui/`, `react-native-elements` imports
ERROR	`nav-native-stack`	`@react-navigation/stack` / `createStackNavigator`
ERROR	`touch-gesture-handler-thread`	`PanResponder`
ERROR	`touch-pressable-feedback`	`TouchableWithoutFeedback`
ERROR	`acc-dynamic-type`	`allowFontScaling={false}`
ERROR	`motion-ui-thread-animation`	`useNativeDriver: false`
ADVISORY	`nav-native-tabs`	`createBottomTabNavigator` (JS tab bar)
ADVISORY	`visual-semantic-colors`	hardcoded hex in `color:`/`backgroundColor:`/`borderColor:`/`tintColor:`
ADVISORY	`visual-system-font`	custom `fontFamily:`
ADVISORY	`system-status-bar`	hardcoded `StatusBar style="dark"/"light"`
ADVISORY	`motion-virtualized-lists`	a file using both `<ScrollView>` and `.map(`

Each finding links to expo-ios-hig/references/{rule}.md (path configurable in config.json) for the explanation and fix.

Setup

config.json is optional — sensible defaults apply. Override on first use if your project differs:

search_roots — space-separated source dirs to scan (default app src components)
skill_rules_dir — path used in report links to the expo-ios-hig rule files (default ../expo-ios-hig/references)

If jq is installed, the script reads these from config.json; otherwise it uses the defaults. rg (ripgrep) is used when available, with a grep fallback — no hard dependency.

How to Use

Run scripts/verify-hig.sh against the Expo project root.
Read the grouped report; open the linked rule file for any finding to see the fix.
Treat ERRORS as must-fix before shipping; review ADVISORIES (they include intentional exceptions).
To extend: add a check ERROR|ADVISORY <rule> "<message>" "<regex>" line in run_checks() — see references/workflow.md.

Related Skills

expo-ios-hig — the rules this verifier checks; every finding links back to it.
expo-ios-screen-scaffolder — generates screens that pass these checks by construction.

expo-ios-hig-verify