Add support for IntelliJ formatting

[Gaming32]

This would accept an IntelliJ formatting XML file and run IntelliJ's formatter.

[lukebemish]

Do you have a link to that formatter and/or something using it? Could totally look at that.

[Swedz]

I second this request! While we can export to Eclipse formatting from IntelliJ, that does lose some context. Which causes formatting changes that do not happen when running the IntelliJ formatter.

Spotless does have an implementation for IntelliJ formatting. Some pitfalls of their implementation I am aware of are:

• It does require IntelliJ be installed. Which complicates things when trying to run the formatter by a GitHub action, for example.
• They execute a command for each file that runs the IntelliJ executable. This makes running the process extremely slow.

[lukebemish]

Executing a command per file would be extremely slow; and if it requires IJ to be installed, there's no advantage over just running it from within IJ instead, right? Seeing as you can't make use of it on CI anyways. If IJ's formatter is available in some library I can depend on and call from immaculate, I'm more than glad to add integration, but otherwise I can't see the benefit?

[Swedz]

My thoughts exactly.

I believe what you would want is the IntelliJ Platform SDK, specifically the PSI. It does appear to be specifically for making plugins and part of the SDK as a whole, so I'm not sure if the formatting portion can be isolated. Though I'm not very familiar with it so I may be missing something.

[lukebemish]

PSI isn't too much of a pain to work with and I've poked it before; my question was more which piece of that the formatter is actually included in. But I'll give it a poke if I have some free time; due to being fairly busy right now I can't guarantee when that will be (though PRs are always appreciated too).