Comments in ?eval command delete everything after it

[kangalio]

Bug description

I thought this was a bug, but apparently it's a feature...?

RustbotPython/bot/cogs/playground.py

Lines 76 to 83 in 25ecd0e

	async def eval(self, ctx: commands.Context, *, arg):
	"""Evaluates Rust code and debug prints the results. Exactly equal to https://play.rust-lang.org/"""
	(mode, code) = self.parse_args(arg)
	comment_index = code.source.find("//")
	end_idx = comment_index if comment_index != -1 else len(code.source)
	await self.send_playground(
	ctx, mode, 'fn main(){println!("{:?}",{' + code.source[:end_idx] + "});}"
	)

It deliberately deletes everything after the occurence of //. I imagine this is a very blunt workaround to prevent comments on the last line from shadowing the closing brackets });}. However, this is much better done by just putting the user input into their own lines:

'fn main(){println!("{:?}",{\n' + code.source[:end_idx] + "\n});}'

Why fix this

This bug peculiarity just cost me about 10 minutes of headaches because I couldn't figure out why this snippet of code complained about lifetimes:

let strings = vec!["zone", "abigail", "theta", "form", "libe", "zas", "theta", "abigail"];
let k = 2;

strings
  .windows(k)
  .rev() // prefer first match instead of last
  .max_by_key(|window| window.iter().map(|string| string.len()).sum::<usize>())
  .unwrap()
  .join("")

Also

On that note, might as well get the formatting correct once and for all. You could replace

'fn main(){println!("{:?}",{' + code.source[:end_idx] + "});}"'

with

'''
fn main() {
	println!("{:?}", {
		%s
	});
}
'''.format("\n\t\t".join(code.source.splitlines()))

That way, error messages will have nicely formatted code (right) instead of the ugly minified code (left)