What mechanisms exist for documenting code in Kotlin?

In Kotlin, KDoc is used for documenting code, based on the JavaDoc syntax.

Main elements of KDoc:

• Documentation blocks: Start with /** and end with */. They are placed before a class, function, property, or other entity to describe.
• Description: The first line in the documentation block is a brief description. A more detailed description can follow after an empty line.
• Tags: Used to provide structured information. Some common tags:
  • @param <parameter name> <description>: Describes a function or constructor parameter.
  • @return <description>: Describes the return value of a function.
  • @constructor <description>: Describes a class constructor.
  • @throws <exception type> <description>: Describes an exception that may be thrown.
  • @sample <full function name>: Provides an example of using the documented entity.
  • @author <name>: Indicates the author of the code.
  • @since <version>: Indicates the version in which the entity was added.
  • @see <destination item>: Refers to another related documentation element.

Example of using KDoc:

/**
 * This class represents a user.
 *
 * @property name User's name.
 * @property age User's age.
 */
class User(
    val name: String,
    val age: Int
) {

    /**
     * Greets the user.
     *
     * @param greeting Greeting message.
     * @return String with greeting and user's name.
     * @throws IllegalArgumentException If the greeting is empty.
     */
    fun greet(greeting: String): String {
        if (greeting.isEmpty()) {
            throw IllegalArgumentException("Greeting cannot be empty")
        }
        return "$greeting, $name!"
    }
}

Generating documentation:

To generate documentation from KDoc, you can use:

• Dokka: The official tool for generating Kotlin documentation. Supports various output formats (HTML, Markdown, JSON, etc.) and can generate documentation for mixed projects (Kotlin, Java, Scala). Integrates with Gradle and Maven.
• IDE plugins: IntelliJ IDEA and Android Studio have built-in support for KDoc and allow viewing documentation in pop-up windows and generating HTML documentation (based on Dokka).

Additional features:

• Markdown: Basic Markdown syntax can be used inside KDoc blocks for text formatting (bold, italics, lists, links).
• Links: You can create links to other classes, functions, or properties using the [<destination>] syntax.

KDoc is a powerful tool that helps create readable and maintainable documentation for Kotlin code. Regular use improves team understanding of the code and facilitates further development.