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To generate source code from any KType, including information that’s not accessible to the builtin reflection APIs, KotlinPoet depends on kotlin-reflect. kotlin-reflect can read the metadata of your classes and access this extra information. KotlinPoet can for an example, read the type parameters and their variance from a generic KType and generate appropriate source code.

kotlin-reflect is a relatively big dependency though and in some cases it is desirable to remove it from the final executable to save some space and/or simplify the proguard/R8 setup (for example for a Gradle plugin that generates Kotlin code). It is possible to do so and still use most of the KotlinPoet APIs:

dependencies {
  implementation("com.squareup:kotlinpoet:<version>") {
    exclude(module = "kotlin-reflect")

The main APIs that require kotlin-reflect are KType.asTypeName() and typeNameOf<T>(). If you’re calling one of these without kotlin-reflect in the classpath and the type is generic or has annotations you will get a crash.

You can replace it with code that passes type parameters or annotations explicitly and doesn’t need kotlin-reflect. For example:

// Replace
// kotlin-reflect needed
val typeName = typeNameOf<List<Int?>>()

// With
// kotlin-reflect not needed
val typeName =
  List::class.asClassName().parameterizedBy(Int::class.asClassName().copy(nullable = true))