Type Definition Generator

Type Definition Generator

Prerequisites & Dependencies

• Node.js 18+ or Python 3.10+
• npm i -g quicktype or pip install pydantic mypy for code generation
• Sample untyped JSON payloads or Python dicts to generate types from
• Optional: npm i ajv for JSON Schema validation, pip install marshmallow for Python

Execution Steps

1. Collect a representative set of JSON examples (ideally 10–20) covering all branches, nulls, nested objects, and arrays
2. Run a code generator:
   • Quicktype: quicktype input.json -l typescript → produces .d.ts interfaces with JSON Schema annotations
   • Pydantic/Marshmallow: python generate.py → produces class User(BaseModel): ... or schema fields
3. Review the generated types for correctness: verify union types, required/optional markers, enum values
4. Apply the types in the project: import interfaces in TypeScript, use Pydantic models in Python APIs
5. Run type checking: npx tsc --noEmit or mypy pipeline.py to catch mismatches early
6. Iterate: add more JSON samples or adjust generator flags (--enum-as-string, --just-types) until the output matches the project's typing style

# Quicktype: generate TypeScript interfaces from JSON
quicktype src/payloads/user.json -l typescript -o src/types/user.d.ts

# Pydantic example: from dict to typed model
from pydantic import BaseModel, EmailStr

class User(BaseModel):
    id: int
    name: str
    email: EmailStr
    is_active: bool = True

user = User(**{"id": 1, "name": "Alice", "email": "alice@example.com"})