Core Package Development Skill

Core Package Development

The core package (packages/core/) is dependency-free and handles all DSL processing.

Data Flow

DSL (YAML input) → validate() → normalize() → IR → diff() → Patch

Key Files

| File | Purpose | Exports | |------|---------|---------| | types.ts | Type definitions | DSL*, IR*, Patch, WebSocket protocol | | validate.ts | YAML validation | validate(dsl): ValidationResult | | normalize.ts | DSL → IR conversion | normalize(dsl): IRDocument | | diff.ts | IR diff calculation | diff(prev, next): Patch |

Type Hierarchy

DSL Types (user input)      IR Types (normalized)
─────────────────────       ────────────────────
DSLDocument                 IRDocument
  ├─ version: number          ├─ version: number
  ├─ docId: string            ├─ docId: string
  ├─ title?: string           ├─ title: string
  ├─ nodes: DSLNode[]         ├─ nodes: Record<string, IRNode>
  └─ edges?: DSLEdge[]        └─ edges: Record<string, IREdge>

DSLNode                     IRNode
  ├─ id: string               ├─ id: string
  ├─ provider: string         ├─ provider: string
  ├─ kind: string             ├─ kind: string
  ├─ label?: string           ├─ label: string (default: id)
  ├─ parent?: string          ├─ parent: string | null
  └─ layout: DSLLayout        └─ layout: { x, y, w, h }

DSLEdge                     IREdge
  ├─ id: string               ├─ id: string
  ├─ from: string             ├─ from: string
  ├─ to: string               ├─ to: string
  └─ label?: string           └─ label: string (default: "")

Patch Operations

type PatchOp =
  | { op: "upsertNode"; node: IRNode }
  | { op: "removeNode"; id: string }
  | { op: "upsertEdge"; edge: IREdge }
  | { op: "removeEdge"; id: string };

interface Patch {
  baseRev: number;
  nextRev: number;
  ops: PatchOp[];
}

WebSocket Protocol Types

// Plugin → CLI
interface HelloMessage {
  type: "hello";
  docId: string;
  secret?: string;
}

interface RequestFullMessage {
  type: "requestFull";
  docId: string;
}

// CLI → Plugin
interface FullMessage {
  type: "full";
  rev: number;
  ir: IRDocument;
}

interface PatchMessage {
  type: "patch";
  baseRev: number;
  nextRev: number;
  ops: PatchOp[];
}

interface ErrorMessage {
  type: "error";
  message: string;
}

Development Workflow

Modify types → Update types.ts
Update validation → Ensure validate.ts catches invalid input
Update normalization → Handle new fields/defaults in normalize.ts
Update diff → Handle new patch scenarios in diff.ts
Add tests → Co-located *.test.ts files
Run tests → bun test packages/core/

Testing

# All core tests
bun test packages/core/

# Specific test file
bun test packages/core/src/diff.test.ts
bun test packages/core/src/validate.test.ts
bun test packages/core/src/normalize.test.ts

# Watch mode
bun test --watch packages/core/

Common Patterns

Adding a new node property

Add to DSLNode and IRNode in types.ts
Add validation in validate.ts
Add default value handling in normalize.ts
Update diff logic if property affects equality
Add test cases for validation, normalization, and diff

Adding a new edge property

Add to DSLEdge and IREdge in types.ts
Add validation in validate.ts
Add default value handling in normalize.ts
Update diff logic for edge equality check
Add test cases

Agent Skills: Core Package Development

Install this agent skill to your local

Skill Files