typescript

Instruction file imported from Nadil-Dulnidu/estava-mobile-app (.github/instructions/typescript.instructions.md). Copyright stays with the author.

TypeScript strict mode is required. These rules apply to every .ts and .tsx file.

Types

• No any without an explanatory comment justifying why it's unavoidable
• No @ts-ignore without an explanatory comment
• All exported functions must have explicit return type annotations
• Prefer type for object shapes; use interface only when extension via extends is needed
• Use unknown instead of any when the type is genuinely not known — then narrow it

Naming

• Variables and functions: camelCase
• Types and interfaces: PascalCase
• Module-level constants: UPPER_SNAKE_CASE
• Files: kebab-case.ts for utilities, PascalCase.ts for class/type definitions

Functions

• Maximum 50 lines per function — extract helpers if exceeded
• Single responsibility — one function does one thing
• Pure functions preferred — avoid side effects unless necessary
• No deeply nested callbacks (max 3 levels)

Imports

Order imports in this sequence, each group separated by a blank line:

1. External packages (import ... from 'package')
2. Framework imports (import ... from 'sveltekit' / 'next' / etc.)
3. Internal aliases (import ... from '$lib/...')
4. Relative imports (import ... from './...')

Error Handling

• Never use empty catch blocks — at minimum log the error
• Use typed errors — catch (error: unknown) then narrow with instanceof
• Fail fast with descriptive messages at system boundaries
• Validate all external input before use — never trust API responses, user input, or file content

Security (API boundaries)

• Validate all user input before processing
• Never pass raw input to file paths, SQL queries, shell commands, or HTML templates
• Use parameterized queries — never string-interpolate into SQL
• Sanitize before rendering dynamic content as HTML