IntelliJ IDEA Flatpak Setup Guide

IntelliJFlatpak.md

IntelliJ IDEA Flatpak Setup Guide

In this guide I collect all the things I had to manually set up after installing IntelliJ using Flatpak on Linux. Also mostly applicable to other JetBrains IDEs like PHPStorm, WebStorm, Rider, PyCharm etc.

Java versions

Flatpak uses an isolated environment to install the latest version of (usually graphical) applications without having to rely on installed system libraries and such with varying versions.

To use IntelliJ for JVM-based development (Java, Kotlin, Scala etc.) you need a Java Development Kit (JDK).

You can select the JDK location using File -> Project Structure -> JDKs -> plus icon at the top

Using Flatpak, you have three options (although one doesn't really work):

1. Install the JDK system-wide and use that: This way you could use Java outside the Flatpak sandbox as well as inside it. Unfortunately in my experience this usually doesn't work due to different library versions in the sandbox and the system. If you still want to give it a try, the JDK can be accessed in a folder at /var/run/host/lib/jvm/.
2. Install the JDK as a Flatpak SDK: This is what I ended up doing for now, although the third one is easier. This means you can only run Java from Flatpak apps unless you also install Java outside it meaning you have the same JDK version twice.
   • You can do this with flatpak install org.freedesktop.Sdk.Extension.openjdk17 to install JDK 17.
   • Note that you may need to specify the platform version as //22.08 after the name. Check the platform version using flatpak info com.jetbrains.IntelliJ-IDEA-Ultimate
   • The JDK can be accessed at /usr/lib/sdk/openjdk17/jvm/openjdk17 for JDK 17. Note that the outer folder is only the JRE so you need to select the one in the jvm folder.
3. Install the JDK using IntelliJ: This is probably the easiest solution actually. This means only IntelliJ will be able to (easily) use the JDK but that's almost the same as the problem with the second point. Click on File -> Project Structure -> SDKs -> Click the plus icon and select Download JDK

Use the host terminal in the IDE

Since this is an isolated environment, what you get when you open the terminal is a shell inside the Flatpak application. You can only (directly) use tools that are installed by the maintainers. To use other tools, you need to use flatpak-spawn --host <command> as explained by the maintainers themselves.

If you have all the tools you need on your host system, then you might want to use the integrated terminal like a regular host terminal. The default flatpak-spawn command doesn't work well with control characters, so it's better to use host-spawn.

1. Download the latest release for your architecture (likely x86_64).
2. Make the downloaded file executable (right click -> properties or chmod +x host-spawn.x86_64).
3. Move the binary to a path on your... $PATH: sudo mv host-spawn.x86_64 /usr/bin/host-spawn.
4. Open IntelliJ settings, go to Tools -> Terminal and change the shell path to /var/run/host/usr/bin/host-spawn.

Note: You can also move it inside the sandbox if you want it to be only available in there.

GPG signing with password-protected key

IntelliJ uses the sandboxed Git executable by default which uses an included gpg executable by default. The only problem with this is that it fails to ask for a password (according to this issue it was fixed but I still encountered issues with version mismatches).

1. What I ended up doing was writing a small script in a ~/.var/bin folder I created that is accessible to the sandbox by default. The file's contents are:

#!/bin/bash
if [[ -z "$container" ]]; then
	gpg $@
else
	flatpak-spawn --host gpg $@
fi

2. Then I changed Git's config to use this script: git config --global gpg.program ~/.var/bin/gpg.sh. One benefit of using the home folder is that even if Git uses this setting outside Flatpak it still works fine.

The README of host-spawn also outlines a way to do this without creating a script in your home folder but I haven't tried that approach.

Rider Unity integration

I ended up installing both Rider and Unity Hub in flatpak which meant that Rider was not found as a code editor and Unity wanted me to install VSCode. What I ended up doing is pretty similar to the GPG one - just add a script (~/.var/bin/rider.sh) in your home folder (or somewhere accessible to the container):

#!/bin/bash
if [[ -z "$container" ]]; then
	flatpak run com.jetbrains.Rider "$@"
else
	flatpak-spawn --host flatpak run com.jetbrains.Rider "$@"
fi

Then in Unity, under the External Tools section change the External Script Editor to the rider.sh file (browse). It should show up in the list as Rider.

I could open the project from Unity but Rider still complains about the integration.