Show a warning when the config is empty

[fvictorio]

An user could make something like this in the config:

let config: HardhatUserConfig = {
  ...
}

and forget to do export default config. We should show a warning when that happens.

[alcuadrado]

I don't think this is feasible, as a file that doesn't export anything in node is equivalent to one exporting an empty object, and that's a valid config.

[fvictorio]

Oh, I know, but I think it's a good trade-off. We can just check Object.keys(config).length and I think it's way more likely that this helps someone than this annoys a user that explicitly wants an empty config (I don't see why anyone would do that).

[Endlessline]

I took a stab at this, is it something you all think would be useful? It sounds like it still may be up for debate.

[alcuadrado]

Now I get it, @Endlessline, thanks!

I guess I'm ok with that trade-off, as we already print a warning if the user doesn't provide a solidity config.

[fvictorio]

Fixed in hardhat@2.8.1.