Kotlin Contract Extraction

Overview

The Kotlin extractor scans a package directory for .kt files and uses tree-sitter-kotlin to parse them. It identifies classes, object declarations, top-level functions, and extension functions, extracting only public declarations.

API

from goga.contract.kotlin import kotlin_contract

contracts = kotlin_contract("path/to/package")
# Returns list[EntityContract | RoutineContract]

kotlin_contract accepts a path to a Kotlin package directory. Returns an empty list if no .kt files are found.

What Gets Extracted

Source Construct	Contract Type	Notes
class X(val p: T)	EntityContract	Primary constructor params form signature
data class X(...)	EntityContract	Same as regular class
object X { ... }	EntityContract	Signature is always ()
interface X { ... }	EntityContract	Abstract methods collected
fun x(): T	RoutineContract	Top-level public functions
fun X.ext(): T	MethodContract	Extension functions attached to receiver class

Visibility Rules

• Only public declarations are included (Kotlin default is public)
• internal, private declarations are excluded
• companion object members are skipped
• Nullable types (String?) are preserved in signatures

Key Node Types

The parser walks these tree-sitter node types:

• class_declaration -- class, data class, sealed class, interface, and annotation class declarations
• object_declaration -- singleton object declarations
• function_declaration -- top-level and extension functions
• property_declaration -- class properties with type annotations

Example

Given a Kotlin file UserService.kt:

class UserService(val name: String) {
    fun greet(): String = "Hello $name"
}

object Config {
    val host: String = "localhost"
    fun load(): Config = this
}

fun formatName(firstName: String, lastName: String): String =
    "$firstName $lastName"

The extracted contracts are:

Name	Type	Signature
Config	EntityContract	()
UserService	EntityContract	(name: String)
formatName	RoutineContract	(firstName: String, lastName: String) -> String

UserService has one method (greet() -> String). Config has one property (host: String) and one method (load() -> Config).

Extension Functions

Extension functions are attached to their receiver entity. For example:

class User
fun User.greet(): String = "Hello"

The greet method appears on the User entity rather than as a standalone routine.