Panel Extension Starter

A starter template for building panel extensions compatible with @principal-ade/panel-framework-core. This template follows the Panel Extension Store Specification V2 and provides everything you need to create, build, and publish custom panels.

What is a Panel Extension?

Panel extensions are React components distributed via NPM that can be dynamically loaded into panel-compatible host applications. They provide a standardized way to extend application functionality through a plugin-like architecture.

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- NPM Distribution: Published and installed like any NPM package
- Multi-Panel Support: Single package can export multiple related panels
- Framework Integration: Full access to host application context, actions, and events
- Type Safety: Complete TypeScript support with comprehensive type definitions
- Dependency Sharing: Shared dependencies (React, ReactDOM) provided by host
- Self-Contained: Unique dependencies bundled within the panel

Getting Started

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``bash


Clone the starter

git clone https://github.com/your-org/panel-starter.git my-panel-extension
cd my-panel-extension

Install dependencies

bun install

or: npm install

`

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Update package.json with your information:

`json
{
"name": "@your-org/your-panel-name",
"description": "Your panel description",
"author": "Your Name",
"keywords": ["panel-extension"],
"repository": {
"url": "git+https://github.com/your-org/your-panel-name.git"
}
}
`

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Edit src/panels/ExamplePanel.tsx or create new panel components:

`tsx
import React from "react";
import type { PanelComponentProps } from "../types";

export const MyPanel: React.FC = ({
context,
actions,
events,
}) => {
return (



);
};
`

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Update src/index.tsx to export your panel definitions:

`tsx
import { MyPanel } from "./panels/MyPanel";

export const panels = [
{
id: "your-org.my-panel",
name: "My Panel",
icon: "🚀",
description: "My custom panel",
component: MyPanel,
},
];
`

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`bash


Start Storybook for interactive development

bun run storybook

Build Storybook for deployment

bun run build-storybook
`

Storybook will open at http://localhost:6006 with:

- Interactive component documentation
- Multiple panel states and examples
- Live prop editing
- Code snippets

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`bash


Development mode (watch for changes)

bun run dev

Build for production

bun run build

Type checking

bun run typecheck

Linting

bun run lint
`

Project Structure

`
panel-starter/
├── src/
│ ├── panels/
│ │ ├── ExamplePanel.tsx # Your panel components
│ │ └── ExamplePanel.stories.tsx # Storybook stories
│ ├── types/
│ │ └── index.ts # TypeScript type definitions
│ ├── mocks/
│ │ └── panelContext.tsx # Mock providers for Storybook
│ ├── Introduction.mdx # Storybook introduction
│ └── index.tsx # Main entry - export panels array
├── .storybook/
│ ├── main.ts # Storybook configuration
│ └── preview.ts # Storybook preview config
├── dist/
│ └── panels.bundle.js # Built output (generated)
├── package.json # Package configuration
├── tsconfig.json # TypeScript config
├── vite.config.ts # Build configuration
├── eslint.config.js # Linting rules
└── README.md # This file
`

Panel Component API

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Every panel component receives these props:

`typescript
interface PanelComponentProps {
// Access to shared data and state
context: PanelContextValue;

// Actions for host interaction
actions: PanelActions;

// Event system for inter-panel communication
events: PanelEventEmitter;
}
`

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Access repository data and state:

`tsx
const { context } = props;

// Repository information
context.repositoryPath; // Current repository path
context.repository; // Repository metadata

// Data slices
context.gitStatus; // Git status information
context.fileTree; // File tree structure
context.markdownFiles; // Markdown files list

// State management
context.loading; // Loading state
context.refresh(); // Refresh data
context.hasSlice("git"); // Check slice availability
`

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Interact with the host application:

`tsx
const { actions } = props;

// File operations
actions.openFile?.("path/to/file.ts");
actions.openGitDiff?.("path/to/file.ts", "unstaged");

// Navigation
actions.navigateToPanel?.("panel-id");

// Notifications
actions.notifyPanels?.(event);
`

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Subscribe to and emit panel events:

`tsx
const { events } = props;

// Subscribe to events
useEffect(() => {
const unsubscribe = events.on("file:opened", (event) => {
console.log("File opened:", event.payload);
});

return unsubscribe; // Cleanup
}, [events]);

// Emit events
events.emit({
type: "custom:event",
source: "my-panel",
timestamp: Date.now(),
payload: { data: "value" },
});
`

Panel Definition

Each panel must be defined with metadata:

`typescript
interface PanelDefinition {
id: string; // Unique ID (e.g., 'org.panel-name')
name: string; // Display name
icon?: string; // Icon (emoji or URL)
version?: string; // Version (defaults to package.json)
author?: string; // Author (defaults to package.json)
description?: string; // Short description
component: React.FC; // The panel component

// Optional lifecycle hooks
onMount?: (context) => void | Promise;
onUnmount?: (context) => void | Promise;
onDataChange?: (slice, data) => void;
}
`

Lifecycle Hooks

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Called for individual panels:

`typescript
{
id: 'my-panel',
component: MyPanel,

onMount: async (context) => {
console.log('Panel mounted');
if (context.hasSlice('git')) {
await context.refresh();
}
},

onUnmount: async (context) => {
console.log('Panel unmounting');
// Cleanup logic
},

onDataChange: (slice, data) => {
console.log(Data changed: ${slice}, data);
},
}
`

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Called once for the entire package:

`typescript
export const onPackageLoad = async () => {
console.log("Package loaded");
// Initialize shared resources
};

export const onPackageUnload = async () => {
console.log("Package unloading");
// Cleanup shared resources
};
`

Building and Publishing

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The build process (via Vite) automatically:

- Externalizes React and ReactDOM (provided by host)
- Bundles all other dependencies
- Generates TypeScript declarations
- Creates source maps
- Outputs to dist/panels.bundle.js

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Link your panel locally for testing:

`bash


In your panel directory

bun run build
bun link

In your host application

bun link @your-org/your-panel-name
`

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`bash


Build the package

bun run build

Verify the output

ls -la dist/

Publish to NPM

npm publish --access public
`

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`bash


In the host application


npm install @your-org/your-panel-name
`

The host application will automatically discover your panel by the panel-extension keyword in package.json.

Best Practices

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Use reverse domain notation for panel IDs:

`typescript
id: "com.company.feature-panel"; // ✅ Good
id: "my-panel"; // ❌ Bad (collision risk)
`

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Always handle errors gracefully:

`tsx
const [error, setError] = useState(null);

useEffect(() => {
const loadData = async () => {
try {
if (!context.hasSlice("git")) {
throw new Error("Git data not available");
}
// Use data...
} catch (err) {
setError(err);
}
};
loadData();
}, [context]);

if (error) {
return

;
}
`

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Show loading indicators:

`tsx
if (context.loading || context.isSliceLoading("git")) {
return

;
}
`

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Always unsubscribe from events:

`tsx
useEffect(() => {
const unsubscribe = events.on("event:type", handler);
return unsubscribe; // Cleanup on unmount
}, [events]);
`

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Use provided types for type safety:

`tsx
import type { PanelComponentProps, GitStatus } from "./types";

const MyPanel: React.FC = ({ context }) => {
const gitStatus: GitStatus = context.gitStatus;
// ...
};
`

Available Data Slices

Panels can access these data slices from the host:

| Slice | Type | Description |
| ---------- | ---------------- | ---------------------------- |
| git | GitStatus | Git repository status |
| markdown | MarkdownFile[] | Markdown files in repository |
| fileTree | FileTree | File system tree structure |
| packages | PackageLayer[] | Package dependencies |
| quality | QualityMetrics | Code quality metrics |

Check availability before use:

`tsx
if (context.hasSlice("git") && !context.isSliceLoading("git")) {
// Use git data
}
`

Event Types

Standard panel events:

| Event | Description | Payload |
| -------------------- | ------------------ | ---------------------- |
| file:opened | File was opened | { filePath: string } |
| file:saved | File was saved | { filePath: string } |
| file:deleted | File was deleted | { filePath: string } |
| git:status-changed | Git status changed | GitStatus |
| git:commit | Git commit made | { hash: string } |
| git:branch-changed | Branch changed | { branch: string } |
| panel:focus | Panel gained focus | { panelId: string } |
| panel:blur | Panel lost focus | { panelId: string } |
| data:refresh | Data was refreshed | { slices: string[] } |

Dependencies

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These are provided by the host application:

- react >= 19.0.0
- react-dom >= 19.0.0

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- @principal-ade/panel-framework-core - For advanced panel features

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Include any libraries unique to your panel:

`json
{
"dependencies": {
"lodash": "^4.17.21",
"date-fns": "^2.29.0",
"your-custom-lib": "^1.0.0"
}
}
`

These will be bundled into your panel output.

Troubleshooting

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Ensure package.json has:

`json
{
"keywords": ["panel-extension"],
"main": "dist/panels.bundle.js"
}
`

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Check that peer dependencies are externalized in vite.config.ts:

`typescript
external: ["react", "react-dom"];
`

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Ensure TypeScript can find types:

`bash
bun run typecheck
`

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Check browser console and ensure:

- Panel ID is unique
- Required exports are present (panels` array)
- Component is a valid React component

Resources

- Panel Extension Store Specification V2
- Panel Framework Core
- Example Implementations

License

MIT © Your Name

Contributing

Contributions welcome! Please read the contributing guidelines first.

Support

For issues and questions:

- GitHub Issues
- Discussions