Plugin vs KSP
- Kotlin course
- Expert
- Lesson 15/47
- 5 min
Learn the difference between compiler plugins and KSP.
Plugin vs KSP
A compiler plugin and KSP both run at compile time, but their power and complexity differ. KSP only reads symbols; a plugin can transform the whole AST.
KSP is simpler and stable; it is ideal for code generation (Room, Moshi). A plugin is more powerful but more complex; it is necessary to modify existing code (all-open, no-arg, compose). A plugin offers class open marking, synthetic constructors and IR transforms that KSP cannot do. When building a tool, ask first whether KSP is enough; if not, consider a plugin.
When to use which?
If you only generate new code, KSP is enough. If you need to modify existing classes (make open, add a constructor, transform IR) you need a plugin.
Example: generating a DAO from an @Entity annotation needs only KSP. But to make Spring's @Configuration open for a CGLIB proxy, the all-open plugin is used. UI frameworks like Compose use a plugin to transform @Composable functions at compile time. This distinction affects architecture decisions.
Practice Write the mode comparison
Define data class Mode(val name: String, val level: String). In main, build listOf(Mode("Plugin", "AST"), Mode("KSP", "Symbol")). For each, write println("${'$'}{it.name}: ${'$'}{it.level}").
Starter code
// add the Mode data class
fun main() {
// create two modes and print
}Sample solution
data class Mode(val name: String, val level: String)
fun main() {
val modes = listOf(Mode("Plugin", "AST"), Mode("KSP", "Symbol"))
modes.forEach { println("${it.name}: ${it.level}") }
}Expected output
Plugin: AST KSP: Symbol
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match plugin and KSP
| Term | Meaning |
|---|---|
KSP |
Symbol reading |
Plugin |
AST transform |
all-open |
Makes class open |
Room |
KSP-using library |
2 Which is needed to make a class open?
- Only KSP
- Compiler plugin (all-open) Correct answer
- Runtime reflection
- Only an IDE setting
Explanation: Making a class open modifies existing code; only a plugin can do that.
3 Complete the mode list
val modes = listOf(Mode("Plugin", "AST"), Mode("____", "Symbol"))val modes = listOf(Mode("Plugin", "AST"), Mode("KSP", "Symbol"))Explanation: KSP works at symbol level.