Ktlint precommit is not compatible with JDK 17

[crisidev]

We use https://github.com/macisamuele/language-formatters-pre-commit-hooks with pre-commit to autoformat code during commit.

Our config is using revision v1.6.1 of this hook, which is failing with JDK 17 with the error

Exception in thread "main" java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: Could not initialize class org.jetbrains.kotlin.com.intellij.openapi.util.objectTree.ThrowableInterner

After updating macisamuele/language-formatters-pre-commit-hooks to available version (v2.3.0), the error become more clear:

openjdk version "17.0.3" 2022-04-19 LTS
OpenJDK Runtime Environment Corretto-17.0.3.6.1 (build 17.0.3+6-LTS)
OpenJDK 64-Bit Server VM Corretto-17.0.3.6.1 (build 17.0.3+6-LTS, mixed mode, sharing)

Traceback (most recent call last):
...
language_formatters_pre_commit_hooks.pre_conditions.ToolNotInstalled: JRE: version < 16.0 is required to run this pre-commit hook.
Make sure that you have it installed and available on your path.
Download/Install URL: https://www.java.com/en/download/

[rcoh]

can we manually set the env of the pre-commit hook to be something like JAVA_HOME=<java 11> <run hook>?

[jdisanti]

Ktlint (version 0.46 at time of writing) technically works on JDK 16+ according to its own changelog, but it looks like it requires finicky JVM args in order to do so. For example, the Ktlint CLI automatically adds --add-opens java.base/java.lang=ALL-UNNAMED if it detects Java 16+.

The pre-commit hook has no way of adding JVM args, and even explicitly prohibits JDK 16+ in the most recent versions. I decided to play around with making pre-commit call into Gradle to run Ktlint instead of using the hook:

.pre-commit.config.yaml:

- repo: local
  hooks:
  # ...
  - id: ktlint
    name: Ktlint
    entry: ./.pre-commit-hooks/ktlint.py
    language: python
    files: ^.*\.kt$

.pre-commit-hooks/ktlint.py:

import os
import sys
import subprocess

# Runs a shell command
def run(command):
    subprocess.run(command, stdout=sys.stderr, stderr=sys.stderr, shell=False, check=True)

# Returns the output from a shell command. Bails if the command failed
def get_cmd_output(command):
    result = subprocess.run(command, capture_output=True, shell=False, check=True)
    return result.stdout.decode("utf-8").strip()

def main():
    repo_root = get_cmd_output(["git", "rev-parse", "--show-toplevel"])
    os.chdir(repo_root)

    file_list = ':'.join(sys.argv[1:])
    run(["./gradlew", "ktlintPreCommit", f"-Pktlint.filelist={file_list}"])

if __name__ == "__main__":
    main()

build.gradle.kts:

tasks.register<JavaExec>("ktlintPreCommit") {
    description = "Run by pre-commit to check files"
    group = "formatting"
    classpath = configurations.getByName("ktlint")
    main = "com.pinterest.ktlint.Main"
    // Fixes Ktlint for Java 16+: https://github.com/pinterest/ktlint/issues/1195#issuecomment-1009027802
    jvmArgs = listOf("--add-opens=java.base/java.lang=ALL-UNNAMED")
    args = listOf("-F") + project.property("ktlint.filelist")!!.toString().split(":")
}

This got me passed the NoClassDefFoundError, but ultimately I encountered something new:

Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private transient java.lang.Object java.lang.Throwable.backtrace accessible: module java.base does not "opens java.lang" to unnamed module @d310a75

It seems Ktlint still doesn't actually work on JDK 17, even with the JVM args hack. When that gets fixed, then we can revisit this approach if the pre-commit hook is still not updated.

can we manually set the env of the pre-commit hook to be something like JAVA_HOME=<java 11> <run hook>?

The pre-commit hook documents how to work with multiple JDK versions to work around this, but I don't like the additional setup that is required for it. There's also a way to run it in Docker, but then installing Docker is required to run Ktlint.