library: Add Rust file for demos without code

[Hofer-Julian]

No description provided.

[sonnyp]

Why?

[Hofer-Julian]

Why?

Because od the way the previewer is set up. The demos without Javascript code don't compile in Rust.
The Vala demos have the same problem.

[sonnyp]

I see, the problem is when opening a Library demo that is not ported yet and pressing "Run".
I don't think making it compile nothing is the right solution. With these changes it will "fail" silently and possibly confuse users.

We currently show this in the Code panel and an error in the console (at least for Rust) which is more useful.

// Sorry, this demo is not available in Rust yet.

Here are a couple of non exclusive ideas:

When the demo is not available in the currently selected Code lang

• Force open the Code panel (to make sure the comment is visible)
• Disable the Run button
• Automatically Switch to JavaScript

[Hofer-Julian]

I see, the problem is when opening a Library demo that is not ported yet and pressing "Run".

This is about demos that have no javascript code, not demos that are not ported yet :)

[Hofer-Julian]

Should have been more specific in the PR, sorry for that.

[sonnyp]

Ha, gotcha.

I wonder if we shouldn't just hide the Run button in that case since it does nothing anyway and might confuse beginners. WDYT?

[sonnyp]

Let's chat, will be easier.

[Hofer-Julian]

For context, @sonnyp and I agreed that the approach in this PR makes the most sense for now.
@lw64 I've also did the same for Vala, seems to work fine as far as I can tell.

[lw64]

If its not too much work for you, it would be nice to havea line brak after the {, but its really not important.

[lw64]

But thanks for the work :)

[sonnyp]

Thank you !

Regarding the line break, I'll take care of it, the Vala formatter will fix it