Allow running Effekt programs directly from VS Code

[marzipankaiser]

AFAICT, there is currently no way to run Effekt programs from the VS Code GUI. (Apart from opening the terminal and running it directly).

[b-studios]

Yes, that's right. Of course, you could use the terminal built into vscode; probably that's what you meant.

Some languages (like Flix) have vscode support where run shows up as a codelens over a toplevel function.
For this, we would need some support from our compiler, I'd assume. At least, we could generate a main that calls this particular function and run it immediately (like it is done in the Repl).

https://github.com/effekt-lang/effekt/blob/master/effekt/jvm/src/main/scala/effekt/Repl.scala#L293-L321

[jiribenes]

This would be already very helpful even if it worked only for def main(): Unit / {} and ran the whole file with the currently chosen backend.

[b-studios]

For all other functions that take no argument and don't have unhandled effects, it is very easy to generate main as a thin wrapper and can it immediately. In the Repl we do something very similar

[jiribenes]

Sure, though it would be very interesting to have this for the Effekt practicals already (so within the next ~month), but I really don't have the time to do this myself.

[jiribenes]

#28 has a crude version that greps for def main() in a file and shows a |> Run code lens above it that runs the whole file like effekt $CURRENT_FILE --backend $BACKEND.
There was also an attempt to open the REPL, but it fails on a few details mentioned in #28. Here's the relevant commit that reverts from REPL back to running a file (you can just apply it in reverse): 5a12148

That's why I don't consider this issue resolved (yet), please feel free to pick this up and continue with a better solution. :)

[jiribenes]

Possible heuristic as an improvement: if there are two def main()s, do not show the run button (can we show some error there?)