Migrate from error_chain?

[ehuss]

error_chain is mostly unmaintained now, I think it would be a good idea to move off it. I only have experience with failure, so that would be my preference as an alternative. But if anyone prefers something else, it would be good to discuss!

[shepmaster]

anyone prefers something else

I'd like to humbly suggest SNAFU. I think it's the bee's knees.

Is there anything concretely disliked about the current implementation that I could watch out for when preparing a PR for discussion?

[shepmaster]

Some thoughts on a first skim:

• There are a lot of stringly-typed errors; basically any use of error_chain:

  utils::fs::remove_dir_content(&build_dir)
      .chain_err(|| "Unable to clear output directory")?;

• Errors that could provide more information. In the same example, it would be nice to know what directory was unable to be cleared.

• Multiple errors don't expose any context. For example, I'm pretty sure that this error would be very hard for an end-user to debug, because it's not obvious why we are creating a directory:

  if !parent.exists() {
      fs::create_dir_all(parent)?;
  }

[shepmaster]

Does mdBook have a minimum Rust version it targets? I'm seeing a few places that could make use of newer Rust features (like fs::read_to_*).

[shepmaster]

I've moved a few modules over to SNAFU, if anyone is interested in checking it out or providing early-stage feedback.

[ehuss]

Closing as error_chain was dropped for anyhow in #1211.