frontend-developer

name	frontend-developer
description	Build user interfaces using Redpanda UI Registry components with React, TypeScript, and Vitest testing. Use when user requests UI components, pages, forms, or mentions 'build UI', 'create component', 'design system', 'frontend', or 'registry'.

Frontend UI Development

Build UIs using the Redpanda UI Registry design system following this repo's patterns.

Critical Rules

ALWAYS:

• Fetch registry docs FIRST: Invoke mcp__context7__get-library-docs with library /websites/redpanda-ui-registry_netlify_app
• Use registry components from src/components/redpanda-ui/
• Install components via CLI: yes | bunx @fumadocs/cli add --dir https://redpanda-ui-registry.netlify.app/r <component>
• Use functional React components with TypeScript
• Run bun i --yarn after installing packages

NEVER:

• Use deprecated @redpanda-data/ui or Chakra UI
• Modify files in registry base directory (check cli.json)
• Copy/paste registry source code
• Add margin className directly to registry components
• Use inline style prop on registry components
• Leave console.log or comments in code

Workflow

1. Fetch Registry Documentation

# REQUIRED FIRST STEP
Invoke: mcp__context7__get-library-docs
Library: /websites/redpanda-ui-registry_netlify_app

2. Install Components

# Single component
yes | bunx @fumadocs/cli add --dir https://redpanda-ui-registry.netlify.app/r button

# Multiple components (space-separated)
yes | bunx @fumadocs/cli add --dir https://redpanda-ui-registry.netlify.app/r card dialog form

# Then generate yarn.lock
bun i && bun i --yarn

3. Write Component

Structure:

// Functional component with explicit types
interface Props {
  title: string
  onSubmit: (data: FormData) => void
}

export function MyComponent({ title, onSubmit }: Props) {
  // Component logic
}

Styling:

// ✅ CORRECT: Use component variants
<Button variant="primary" size="lg">Click</Button>

// ✅ CORRECT: Wrap for spacing
<div className="mt-4">
  <Button variant="primary">Click</Button>
</div>

// ❌ WRONG: Direct margin on component
<Button className="mt-4" variant="primary">Click</Button>

TypeScript:

• Define prop interfaces
• Never use any - infer correct types
• Use generics for collections

Performance:

• Hoist static content outside component
• Use useMemo for expensive computations - but only when there's a noticeable performance impact
• Use memo for components receiving props

4. Write Tests

Test types:

• Unit tests (.test.ts): Pure logic, utilities, helpers - Node environment
• Integration tests (.test.tsx): React components, UI interactions - JSDOM environment

Unit test example:

// utils.test.ts
import { formatNumber } from './utils'

describe('formatNumber', () => {
  test('should format numbers with commas', () => {
    expect(formatNumber(1000)).toBe('1,000')
  })
})

Integration test example:

// component.test.tsx
import { render, screen, fireEvent, waitFor } from 'test-utils';
import { createRouterTransport } from '@connectrpc/connect';
import { createPipeline } from 'protogen/redpanda/api/console/v1alpha1/pipeline-PipelineService_connectquery';
import { MyComponent } from './component';

describe('MyComponent', () => {
  test('should trigger gRPC mutation when form is submitted', async () => {
    // Mock the gRPC service method
    const mockCreatePipeline = vi.fn(() =>
      Promise.resolve({ id: '123', name: 'test-pipeline' })
    );

    // Create a mocked transport
    const transport = createRouterTransport(({ rpc }) => {
      rpc(createPipeline, mockCreatePipeline);
    });

    // Render with the mocked transport
    render(<MyComponent />, { transport });

    // Fill out the form
    fireEvent.change(screen.getByLabelText('Pipeline Name'), {
      target: { value: 'test-pipeline' }
    });

    // Submit the form
    fireEvent.click(screen.getByRole('button', { name: 'Create' }));

    // Verify the mutation was called with correct data
    await waitFor(() => {
      expect(mockCreatePipeline).toHaveBeenCalledWith({
        name: 'test-pipeline'
      });
    });
  });
});

Mocking:

vi.mock('module-name', async (importOriginal) => {
  const actual = await importOriginal<typeof import('module-name')>()
  return {
    ...actual,
    functionToMock: vi.fn(),
  }
})

const mockFunction = vi.mocked(functionToMock)

5. Validation

# Run in order
bun run type:check            # TypeScript errors
bun run test                  # All tests
bun run lint                  # Code quality
bun run build                 # Production build
bun run start2 --port=3004    # Dev server - check browser

Success criteria:

• ✓ No TypeScript errors
• ✓ All tests passing
• ✓ No lint errors
• ✓ Build succeeds
• ✓ No runtime errors in browser

Testing Commands

bun run test                 # All tests (unit + integration)
bun run test:unit            # Unit tests only (.test.ts)
bun run test:integration     # Integration tests only (.test.tsx)
bun run test:watch           # Watch mode
bun run test:coverage        # Coverage report

Common Patterns

Registry Component Usage

Check src/components/redpanda-ui/ for installed components before installing new ones.

Use component variants instead of custom styling:

<Button variant="primary" size="lg" />
<Card variant="outline" />
<Dialog size="md" />

Form Patterns

For complex forms, use React Hook Form + Zod:

import { useForm } from 'react-hook-form'
import { zodResolver } from '@hookform/resolvers/zod'
import { z } from 'zod'

const schema = z.object({
  name: z.string().min(1),
  email: z.string().email(),
})

const form = useForm({
  resolver: zodResolver(schema),
  defaultValues: { name: '', email: '' },
})

For simple forms, use AutoForm:

import { AutoForm } from '@autoform/react';
import { ZodProvider } from '@autoform/zod';

<AutoForm
  schema={schema}
  onSubmit={handleSubmit}
  provider={ZodProvider}
/>

Reusable Sub-Components

Create sub-components in the same file when logic repeats:

export function FeatureComponent() {
  return (
    <div>
      <FeatureHeader />
      <FeatureContent />
    </div>
  );
}

// Colocated sub-components
function FeatureHeader() { /* ... */ }
function FeatureContent() { /* ... */ }

Testing Best Practices

File naming:

• .test.ts for utilities and pure functions (unit tests)
• .test.tsx for React components (integration tests)

Mock location:

• Use pre-configured mocks from src/test-utils/
• Mock external dependencies, not internal code

Render utility:

• Import from test-utils/test-utils.tsx for component tests
• Includes all providers (React Query, Router, Auth0)

Async testing:

• Use waitFor for async operations
• Test loading and error states
• Verify state updates

Quick Reference

Check before installing:

# Check if component exists
ls src/components/redpanda-ui/components/

Multi-component install:

yes | bunx @fumadocs/cli add --dir https://redpanda-ui-registry.netlify.app/r \
  button card dialog form input label select

After package install:

bun i && bun i --yarn  # ALWAYS run this

Testing shortcuts:

• Unit test: Pure function? Use .test.ts
• Integration test: React component? Use .test.tsx
• Mock external: Add to src/test-utils/
• Custom render: Use test-utils/test-utils.tsx

Output

After completing work:

1. Confirm all validation steps passed
2. Summarize what was built
3. Note any runtime checks needed in browser
4. Mention test coverage if relevant