Kotlin Project Rules

kotlinjvmbackend

Enforces Kotlin idioms including coroutines, null safety, data classes, extension functions, and functional patterns for safe and expressive JVM development.

Целевые файлы

Файл	Формат
.cursorrules	plaintext
CLAUDE.md	markdown

Содержимое

## Kotlin Project Rules ### Null Safety - Never use `!!` (not-null assertion) in production code — it hides a design problem - Prefer `?.let { }`, `?: return`, or `?: throw` for null handling - Use `requireNotNull()` and `checkNotNull()` with descriptive messages at function entry points - Design APIs to return `T?` when absence is a valid state; use `Result<T>` for error propagation - Initialize lateinit properties only for dependency-injected fields; document why lateinit is necessary ### Data Classes - Use `data class` for value objects and DTOs — not for entities with identity - Data classes must be immutable: use `val` for all properties - Use `copy()` to create modified instances — never mutate a data class - Override `equals()`/`hashCode()` manually in entity classes based on business identity ### Functions & Lambdas - Prefer expression body for single-expression functions: `fun greet(name: String) = "Hello, $name"` - Use trailing lambda syntax when the last parameter is a lambda: `list.filter { it.active }` - Use `let`, `run`, `with`, `apply`, `also` scope functions purposefully — `apply` for object configuration, `let` for null checks, `also` for side effects - Avoid deeply nested scope functions — flatten with local variables for readability - Prefer immutable collections (`listOf`, `mapOf`, `setOf`); use mutable variants only when mutation is necessary ### Coroutines - Always launch coroutines from a structured scope (`viewModelScope`, `lifecycleScope`, `coroutineScope`) - Never use `GlobalScope` — it has no structured lifecycle - Use `Dispatchers.IO` for I/O operations; `Dispatchers.Default` for CPU-bound work; `Dispatchers.Main` for UI - Use `withContext(Dispatchers.IO)` to switch dispatcher inside a coroutine, not `launch` - Use `supervisorScope` when child coroutine failures should not cancel siblings - Use `flow { }` for streams of data; collect on `Dispatchers.Main` for UI updates - Handle cancellation: check `isActive` in long loops; use `ensureActive()` or `yield()` ### Extension Functions - Write extension functions on standard types to add domain-specific behavior - Keep extension functions in files named after the receiver type: `StringExtensions.kt` - Do not write extension functions that access private/internal members of a class — use member functions - Mark extension functions as `internal` if they are implementation details ### Sealed Classes & When Expressions - Model state machines and ADTs with `sealed class` or `sealed interface` - Always use `when` on sealed types as expressions — exhaustive `when` prevents missing cases - Use `when` without an argument as a cleaner replacement for if-else chains ### Interfaces & Abstract Classes - Prefer interfaces with default implementations over abstract classes for mixins - Use `abstract class` when you need constructors, state, or initialization logic - Mark classes `final` by default (Kotlin default) — explicitly open only classes designed for extension ### Error Handling - Use `Result<T>` for recoverable errors in pure functions - Throw specific exception subclasses; document thrown exceptions in `@Throws` annotation for Java interop - Use `runCatching { }` for wrapping potentially-throwing code; chain `.getOrElse { }` for fallbacks ### Naming & Style - Functions and properties: `camelCase`; classes and objects: `PascalCase`; constants: `UPPER_SNAKE_CASE` - Boolean properties must read as predicates: `isActive`, `hasPermission`, `canEdit` - Companion object constants go inside the class, not at top-level unless truly global ### Anti-patterns - Do not use Java-style static utility classes — use top-level functions or extension functions - Do not use `object` for stateful singletons accessed from multiple coroutines without synchronization - Do not catch `Exception` broadly — catch specific exceptions - Do not block the main thread with `runBlocking` in production Android/server code

CLI

npx mindaxis apply kotlin-rules --target cursor --scope project

Используется в паках

Не используется ни в одном паке

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