Frontend Pattern Scanner Skill

Purpose

Auto-detect frontend (React/Vue/Angular/Svelte) code conventions by scanning the codebase. Works on any project.

Activation

When creating or modifying frontend code and no cached patterns exist yet.

How It Works

This skill does NOT hardcode patterns. Instead, it scans the codebase to discover them. Results are cached in .claude/idev/frontend-patterns/cache.md after first scan.

Phase 1: Detect Frontend Stack

Run these checks to identify the technology:

1. Read package.json → detect framework (react, vue, angular, svelte, next, nuxt)
2. Read package.json → detect key libraries:
   - State: redux, zustand, mobx, pinia, @tanstack/react-query
   - UI: antd, @mui/material, chakra-ui, tailwindcss, bootstrap
   - Routing: react-router-dom, vue-router, @angular/router
   - HTTP: axios, fetch wrapper, @tanstack/react-query
   - Forms: react-hook-form, formik, vee-validate
   - Date: dayjs, moment, date-fns, luxon
3. Read tsconfig.json or jsconfig.json → TypeScript or JavaScript
4. Glob for tailwind.config.* → Tailwind CSS
5. Glob for .eslintrc* → Linting rules

Phase 2: Discover Project Structure

Scan to find the architecture pattern:

1. Read src/ directory structure (ls src/)
2. Detect architecture style:
   - Feature-based: src/features/ or src/modules/
   - Layer-based: src/components/, src/services/, src/hooks/
   - Page-based: src/pages/ or app/ (Next.js/Nuxt)
3. Glob **/*Container*.{tsx,jsx,vue} → Container components
4. Glob **/*Page*.{tsx,jsx,vue} → Page components
5. Glob **/hooks/*.{ts,js} or **/composables/*.{ts,js} → Custom hooks
6. Glob **/services/*.{ts,js} or **/api/*.{ts,js} → API services
7. Glob **/models/*.{ts,js} or **/types/*.{ts,js} → Type definitions
8. Glob **/store/*.{ts,js} or **/slices/*.{ts,js} → State management
9. Grep for "createBrowserRouter|Routes|Route" → Routing setup file
10. Grep for "API_URL|BASE_URL|baseURL" in .env* → API configuration

Phase 3: Extract Patterns from Existing Code

For each discovered layer, read ONE representative file and extract the pattern:

3.1 Component Pattern

Pick one presentation/UI component
Extract: FC typing vs function declaration, props interface pattern, styling approach
Detect: CSS modules, Tailwind, styled-components, inline styles, UI library usage
Note: import ordering convention, export style (default vs named)

3.2 Container/Smart Component Pattern

Pick one container component
Extract: how hooks are used, how data flows to children, callback patterns
Detect: useCallback/useMemo usage, data transformation location, error handling

3.3 Hook Pattern

Pick one custom hook
Extract: return type, query/mutation pattern, error dispatching
Detect: query key pattern, cache invalidation strategy, optimistic updates
Note: query library version (v4 vs v5 differences)

3.4 Service/API Pattern

Pick one service file
Extract: HTTP client (axios instance, fetch wrapper), URL construction, response typing
Detect: interceptors, auth headers, error transformation, base URL config
Note: how API URLs are organized (enum, constants file, inline)

3.5 Type/Model Pattern

Pick one types file
Extract: interface vs type usage, enum style (string enum, const enum, object const)
Detect: DTO types, form data types, API response wrappers

3.6 State Management Pattern

Find store/slice files
Extract: how global state is structured, dispatch patterns
Detect: Redux toolkit, Zustand, Context, or other

3.7 Routing Pattern

Find routing config
Extract: route definition style, route constants, navigation pattern
Detect: lazy loading, guards/middleware, nested routes

Phase 4: Generate Cache

After scanning, write all discovered patterns to: .claude/idev/frontend-patterns/cache.md

Format:

# Frontend Patterns Cache
## Generated: [date]
## Project: [detected project name]
## Stack: [framework] + [UI lib] + [state mgmt] + [query lib]

### Paths
src root: [path]
Components: [path pattern]
Containers: [path pattern]
Hooks: [path pattern]
Services: [path pattern]
Types: [path pattern]
Routes: [file path]
Store: [path pattern]

### Component Template
[extracted pattern with placeholders]

### Container Template
[extracted pattern with placeholders]

### Hook Templates
Query hook: [pattern]
Mutation hook: [pattern]

### Service Template
[extracted pattern with placeholders]

### Type/Interface Template
[extracted pattern]

### Conventions
- Styling: [Tailwind/CSS Modules/styled-components/etc.]
- Exports: [default/named]
- Props: [interface naming]
- File naming: [kebab-case/PascalCase/camelCase]
- Error handling: [pattern]
- Navigation: [pattern]

### Function Index
[Compact list of exported/public functions, one per line:]
functionName — file:line — one-line purpose
[Cap at ~100 entries, most-used first. Used by function-extract for targeted
reads and by cache-refresh for incremental updates. Update entries whenever
adding or modifying functions.]

Phase 5: Usage

On subsequent tasks, load only the cache file instead of rescanning. Keep the cache under ~250 lines by trimming examples if it grows beyond that. Rescan if user says "refresh patterns" or if cache is older than 7 days.

Checklist (generic, auto-populated from scan)

When creating a new frontend feature, the scanner detects what files are needed:

• Types/interfaces in [detected types path]
• Service methods in [detected services path]
• API URL entries in [detected URL config]
• Query/mutation hooks in [detected hooks path]
• Container component in [detected containers path]
• Presentation component in [detected presentation path]
• Route registration in [detected routes file]
• Hook barrel exports in [detected barrel file] (if applicable)