Motivation

despite solar only supporting solidity v0.8.*, foundry needs to be backwards compatible with older versions. For instance, a user who linted a solar-incompatible project was confused to get a bunch of errors foundry-rs/foundry#11668 (comment)

because of that, solar consumers would benefit from:

• treating empty sources as a valid no-op: so that they can filter incompatible sources and call the compiler without worrying about error with no compatible sources left. This would save us from conditionally lowering if we don't have any sources, which is kinda annoying:

  if !compiler.sess().source_map().is_empty() {
      let _ = compiler.lower_asts();
  }

notes:

• as we further integrate solar into more pieces of the stack, this will impact us even more users
• if you think that we should keep the "no files found" error was for CLI consumers, i'd propose to at least support a config param to prevent the error