IntelliJ isn't playing nicely with WSL2

on Development, Java

There’s always a fight against the tooling; I avoided it mostly.

In the midst of my move of all “code related” things into WSL2, I started using Visual Studio Code with the Java extension pack and this works well enough. However, I’m a long time IntelliJ user for Java (I was using their Rust preview but stopped because it’s not that much better than the equivalent vscode extensions). If you search for ‘IntelliJ WSL2’ through your preferred search engine, you’ll find the official documentation that says its supported and you can just point it at a project in \\wsl$\Ubuntu\home\user\project and it’ll be quite happy. I gave it a go, and that’s not my experience.

Before we continue

I’ll admit a few things here, I don’t think any of this is in any way ‘special’ but it’s worth noting:

  1. I install IntelliJ via the Scoop extras bucket. Currently it’s IntelliJ IDEA 2023.2.5 (Community Edition); so we can consider it a Windows install.
  2. My Windows Java instances are managed by sdkman running on wingit bash (I don’t run java via powershell/cmd)
  3. My primary desktop has multiple disks
    • I’m using reparse points as symbolic links (so C:/Users/lewin/.gradle is a symbolic link to D:/storage/.gradle as my NVME drive is smaller than my SSD)
  4. My automount location is / (i.e. /mnt/c is not a thing)1
  5. WSL/Ubuntu is mounted as a network drive W:/.

Problem Statement

  1. Open a project mounted in WSL
  2. Fix the Gradle JVM problem (i.e. point it at one installed in WSL /home/user/.sdkman/...`; it auto detects a few).
  3. Change the JDK in ‘project structure’ to point at the WSL JDK we just selected.

There’s an error in the build log

Running Gradle on WSL...
Error: Could not find or load main class org.jetbrains.plugins.gradle.tooling.proxy.Main
Caused by: java.lang.ClassNotFoundException: org.jetbrains.plugins.gradle.tooling.proxy.Main
Error: Could not find or load main class org.jetbrains.plugins.gradle.tooling.proxy.Main
Caused by: java.lang.ClassNotFoundException: org.jetbrains.plugins.gradle.tooling.proxy.Main

Well, as my daughter would say to me while I’m filling the air with noise about something she’s clearly not interested in: “Cool” while looking pointedly at her phone and ignoring me.

A cursory search on the internet tells me nothing that I didn’t know already; it’s now 2 years after the IDEA 2021.1 EAP release. I know that it’s nothing to do with my gradle installation since ./gradlew compileJava works quite happily on WSL2, and the name of the class suggests that IntelliJ wants to do something special with Gradle. Cool.

So why isn’t $SCOOP/apps/idea/current/IDE/plugins/gradle/lib/gradle.jar in the classpath in this situation when it is when it opens a project on D:\whereever. This is a jar that lives in the IDEA installation directory and solely under the purview of IntelliJ.

bsh ❯ jar -tvf ./plugins/gradle/lib/gradle.jar | grep proxy
...
 26348 Fri Nov 30 00:00:00 GMT 1979 org/jetbrains/plugins/gradle/tooling/proxy/Main.class

I don’t know for sure (I have my suspicions1), and I don’t care; I can continue using Visual Studio Code since it works well enough and keep having everything inside WSL2; Or… we just treat IntelliJ as special; ignore its WSL support and make sure we synchronize things between NTFS & ext4.

Clearly we’re in yet another fight with the tooling. I like things how I like them, and you’re making assumptions that you shouldn’t be making. Making the assumptions is one thing, but not documenting them is always a real pain in the ass.

Enter Mutagen

I’ve been using mutagen for a little while to sync things between my desktop & linux machines elsewhere (it’s what its designed for) so we can use it here to sync things between WSL2 & Windows.

  • Choose a location where you want to sync the code you’re going to open in IntelliJ to; I’m using D:\storage\idea-workdir
  • Create a .mutagen.yml in the root of your project if you have special requirements like ignores and the like.
    • I usually have one for gradle projects where I exclude build and .gradle to avoid too much traffic.
    • I have one for Rust projects that excludes target for the same reason if I want to build on Windows.

This then is a simple script that manages the startup of the synchronisation sessions of the project directory between WSL2 & Windows. I run it on WSL2 only because I’m making a clean break of things and wingit+bash is hidden in Windows Terminal.

#!/usr/bin/env bash

set -eo pipefail

TARGET_BASE=/d/storage/idea-workdir

cfg_args() {
  if [[ -f "$(pwd)/.mutagen.yml" ]]; then
    echo "-c $(pwd)/.mutagen.yml"
  else
    echo ""
  fi
}

sync_fresh() {
  local name
  local target_dir
  sync_stop
  name=$(basename "$(pwd)")
  target_dir="$TARGET_BASE/$name"
  rm -rf "$target_dir"
  sync_start
}

sync_start() {
  local target_dir
  local current_dir
  local name
  current_dir="$(pwd)"
  name=$(basename "$current_dir")
  target_dir="$TARGET_BASE/$name"
  if mutagen sync list | grep "$name" > /dev/null; then
    echo "Already a sync called $name"
  else
    mkdir -p "$target_dir"
    # shellcheck disable=SC2046
    mutagen sync create "$current_dir" "$target_dir" --name "$name" $(cfg_args)
  fi
}

sync_stop() {
  local name
  name=$(basename "$(pwd)")
  if mutagen sync list | grep "$name" > /dev/null; then
    mutagen sync terminate "$name"
  fi
}

sync_list() {
  mutagen sync list
}


check_env() {
  if [[ "$(uname -o | tr '[:upper:]' '[:lower:]')" == "msys" ]]; then echo "Try again on WSL2+Ubuntu"; exit 1; fi
  if ! builtin type -P mutagen > /dev/null; then
    echo "mutagen is not installed"
    exit 1
  fi
}

ACTION=${1:-list}
check_env
sync_"$ACTION"
  • syncfs fresh will stop any existing sync, remove the target directory and create a new one.
    • There is the implicit assumption that the project directory basename is ‘unique’ enough for the target.

Summary

  • If you have changed the mount point for your Windows filesystem, then you need to make a symbolic link between that and /mnt for IntelliJ to be happy.
  • It’s not the fault of IntelliJ that accessing files over //wsl$ is so slow; javac is somewhat IO bound so it’s just not useful.
  • I made IntelliJ dance to my spin on WSL2; well done me, I guess.

mutagen has been acquired by Docker; I have no idea what’s in the future for it. They have a paid for subscription which I’m not using; other tools are available.

  1. If you didn’t realise as soon as I mentioned it; it’s this. I prefer /c over /mnt/c. JetBrains have made a dirty assumption and not for the first time. I symlink shimmed it, but it’s too bloody slow to be usable anyway. ↩︎ ↩︎2

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