Inspecting code on a non-java IntelliJ IDEA project

In my case, I didn't wanted to delete the module since I have a bunch of stuff configured (data sources, dictionaries, http requests) and a lot of code in the shelf (which I believe it's stored along the project/module). I found that you can skip the "delete your module" part and instead just update the module config:

Find the $module.iml file (in my case it's inside the .idea directory) and at the top there's was a line:

<module type="JAVA_MODULE" version="4">

which I changed to:

<module type="WEB_MODULE" version="4">

The issue was fixed and I haven't seen any side-effects but, just in case, you might want to backup the .idea directory.

I raised this over at https://youtrack.jetbrains.com/issue/IDEA-188017 - after some back and forth, the Jetbrains employee helped me figure out that I had a Java module in there.

If you are not using Java, please crate a module of a Static Web type. Now you have a module of a Java type, that is why the error is reported, so such behaviour is expected.

Delete your Java module. Once you enter in the menu in the screenshot below, find the Static Web type and create your module like that.