[SOLVED] IntelliJ IDEA suddenly won't open on Mac "Error occurred during initialization of VM"

IntelliJ IDEA suddenly won't open on Mac "Error occurred during initialization of VM"

IntelliJ IDEA suddenly wouldn't open on my Mac (Intel). The app icon bounces but then nothing happens—no crash report or any kind of message—and there's nothing in Activity Monitor or ps.

Then I tried running it from terminal and got this:

$ /Applications/IntelliJ\ IDEA.app/Contents/MacOS/idea
2023-02-08 07:47:52.953 idea[10131:63714] allVms required 1.8*,1.8+
2023-02-08 07:47:52.955 idea[10131:63717] Current Directory: /Applications/IntelliJ IDEA.app/Contents/MacOS
2023-02-08 07:47:52.955 idea[10131:63717] Value of IDEA_VM_OPTIONS is (null)
2023-02-08 07:47:52.955 idea[10131:63717] fullFileName is: /Applications/IntelliJ IDEA.app/Contents/bin/idea.vmoptions
2023-02-08 07:47:52.955 idea[10131:63717] fullFileName exists: /Applications/IntelliJ IDEA.app/Contents/bin/idea.vmoptions
2023-02-08 07:47:52.956 idea[10131:63717] Processing VMOptions file at /Applications/IntelliJ IDEA.app/Contents/bin/idea.vmoptions
2023-02-08 07:47:52.956 idea[10131:63717] Done
Error occurred during initialization of VM
java.lang.NoClassDefFoundError: com/intellij/util/lang/UrlClassLoader
    at java.lang.ClassLoader.defineClass1(java.base@11.0.13/Native Method)
    at java.lang.ClassLoader.defineClass(java.base@11.0.13/ClassLoader.java:1017)
    at java.security.SecureClassLoader.defineClass(java.base@11.0.13/SecureClassLoader.java:174)
    at jdk.internal.loader.BuiltinClassLoader.defineClass(java.base@11.0.13/BuiltinClassLoader.java:800)
    at jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(java.base@11.0.13/BuiltinClassLoader.java:698)
    at jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(java.base@11.0.13/BuiltinClassLoader.java:621)
    at jdk.internal.loader.BuiltinClassLoader.loadClass(java.base@11.0.13/BuiltinClassLoader.java:579)
    at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(java.base@11.0.13/ClassLoaders.java:178)
    at java.lang.ClassLoader.loadClass(java.base@11.0.13/ClassLoader.java:522)
    at java.lang.Class.forName0(java.base@11.0.13/Native Method)
    at java.lang.Class.forName(java.base@11.0.13/Class.java:398)
    at java.lang.ClassLoader.initSystemClassLoader(java.base@11.0.13/ClassLoader.java:1976)
    at java.lang.System.initPhase3(java.base@11.0.13/System.java:2074)
Caused by: java.lang.ClassNotFoundException: com.intellij.util.lang.UrlClassLoader
    at jdk.internal.loader.BuiltinClassLoader.loadClass(java.base@11.0.13/BuiltinClassLoader.java:581)
    at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(java.base@11.0.13/ClassLoaders.java:178)
    at java.lang.ClassLoader.loadClass(java.base@11.0.13/ClassLoader.java:522)
    at java.lang.ClassLoader.defineClass1(java.base@11.0.13/Native Method)
    at java.lang.ClassLoader.defineClass(java.base@11.0.13/ClassLoader.java:1017)
    at java.security.SecureClassLoader.defineClass(java.base@11.0.13/SecureClassLoader.java:174)
    at jdk.internal.loader.BuiltinClassLoader.defineClass(java.base@11.0.13/BuiltinClassLoader.java:800)
    at jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(java.base@11.0.13/BuiltinClassLoader.java:698)
    at jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(java.base@11.0.13/BuiltinClassLoader.java:621)
    at jdk.internal.loader.BuiltinClassLoader.loadClass(java.base@11.0.13/BuiltinClassLoader.java:579)
    at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(java.base@11.0.13/ClassLoaders.java:178)
    at java.lang.ClassLoader.loadClass(java.base@11.0.13/ClassLoader.java:522)
    at java.lang.Class.forName0(java.base@11.0.13/Native Method)
    at java.lang.Class.forName(java.base@11.0.13/Class.java:398)
    at java.lang.ClassLoader.initSystemClassLoader(java.base@11.0.13/ClassLoader.java:1976)
    at java.lang.System.initPhase3(java.base@11.0.13/System.java:2074)

I tried various things I read online:

I tried removing idea.vmoptions in /Applications/IntelliJ\ IDEA.app/Contents/MacOS/ as well as ~/Library/Application\ Support/JetBrains/<product>/.
I restored them but checked that -Xmx was not smaller than -Xms.
I tried deleting plugins.
I tried restoring the JDK and messing with PATH and environment.

Possible causes were updating from macOS Ventura 13.1 to 13.2 yesterday. Or, installing the bined plugin yesterday.

Solution

Self-answering to help people. Try simply upgrading to the latest IntelliJ IDEA.

For some reason it was the last thing I tried, i.e. downloading the latest .dmg and installing (dragging into Applications and replacing previous version). I was on Ultimate so I downloaded Ultimate, but if you're on CE (Community Edition) you should download that. I guess in the past upgrading IntelliJ caused things to break for me, so I avoided it until I tried everything else. But this time it was the solution. Also for some reason none of the threads I read online mentioned this as the solution—maybe too obvious but hey, I would have tried it sooner if I read it.