DialogWrapper not working with current plugins, ok with next versions

[hamoid]

Describe the bug: I have a working plugin. If I update my plugin matching v1.4.0 of the intellij-platform-plugin-template, a dialog that extends DialogWrapper no longer shows any content, only the OK and Cancel buttons.

Steps to reproduce:

• Create a plugin based on this template, v1.4.0
• Make use of a Dialog extending DialogWrapper. It should contain at least one UI element (a Button, for instance)
• When running the Run Plugin gradle task and opening the Dialog we just created, the Dialog will not display any UI elements except OK, Cancel.

Expected behavior: The UI Elements in the Dialog should be displayed.

Additional context: with kotlin.jvm 1.7.21 and intellij 1.10.0 (working):

with template v1.4.0, kotlin.jvm 1.8.0 and intellij 1.12.0 (broken):

with kotlin.jvm 1.8.10 and intellij 1.13.0 (working):

[hsz]

Can you provide a reproducible project?

[hamoid]

I created one here: https://github.com/hamoid/IPPT/commit/174809dcd6f568935a8885b8f865d398e3ef41cb

In that commit one can see my only changes after creating the plugin. You should be able to clone and run the project. When running the IDE task, immediately it should show a popup window. That window will contain a Label or not, depending on which version of the Gradle IntelliJ Plugin is used.

It is possible that I am using something incorrectly, as I'm not an expert in Swing. But in any case changing the Gradle IntelliJ Plugin version changes the behavior without touching the code (on my system).

[YannCebron]

You cannot use Kotlin to bind with UI Designer forms, see green box https://plugins.jetbrains.com/docs/intellij/user-interface-components.html