Compilation Avoidance

ABI support

rules_kotlin now supports compilation avoidance through the use of ABI jars (also known as interface or header jars) for classpath dependencies. This can have significant performance wins for non-ABI affecting changes since down stream recompilation can be avoided in such cases.

This feature can be enabled through the experimental_use_abi_jars flag in the tool chain as follows

load("//kotlin:core.bzl", "define_kt_toolchain")


define_kt_toolchain(
    name = "kotlin_toolchain",
    experimental_use_abi_jars = True,
)

This feature is implemented using the Jetbrains Kotlin JvmABI compiler plugin for generating headers for Kotlin code. Unfortunately there are some known bugs with this plugin that affect less than 1% of targets.

• https://youtrack.jetbrains.com/issue/KT-40340
• https://youtrack.jetbrains.com/issue/KT-40133

If you encounter such bugs, ABI generation can be disabled on a per target basis by setting the following tag

load("//kotlin:jvm.bzl", "kt_jvm_library")

kt_jvm_library(
    name = "framework",
    tags = ["kt_abi_plugin_incompatible"],
)

Depending on your compiler version you may find non-public symbols in your ABI jar such as internal declarations or effectively private classes. Exclusion of these symbols from the ABI jar can be enabled through the experimental_treat_internal_as_private_in_abi_jars and experimental_remove_private_classes_in_abi_jars flags in addition to experimental_use_abi_jars flag when defining the toolchain as follows

load("//kotlin:core.bzl", "define_kt_toolchain")


define_kt_toolchain(
    name = "kotlin_toolchain",
    experimental_use_abi_jars = True,
    experimental_treat_internal_as_private_in_abi_jars = True,
    experimental_remove_private_classes_in_abi_jars = True,
)

In order to completely remove debug information from the ABI jar, the experimental_remove_debug_info_in_abi_jars flag can be used along with experimental_use_abi_jars

load("//kotlin:core.bzl", "define_kt_toolchain")


define_kt_toolchain(
    name = "kotlin_toolchain",
    experimental_use_abi_jars = True,
    experimental_remove_debug_info_in_abi_jars = True,
)

If you encounter bugs in older compiler versions such as KT-71525 then ABI generation with only public symbols can be disabled on a per target basis by setting the following tags

load("//kotlin:jvm.bzl", "kt_jvm_library")

kt_jvm_library(
    name = "framework",
    tags = [
        "kt_treat_internal_as_private_in_abi_plugin_incompatible", 
        "kt_remove_private_classes_in_abi_plugin_incompatible", 
        "kt_remove_debug_info_in_abi_plugin_incompatible"
    ],
)