Default {} is confusing, while {:#} is much better

[ndmitchell]

We've been using anyhow extensively, and it's worked out great. There's just one super confusing thing. I would expect:

println!("{}", anyhow!("My error message").context("on a file"))

To print at least My error message, and ideally on a file. But it just prints on a file. I know {:#} is available, but I've yet to find a case where we didn't want {:#} and the usage of {} is pretty pervasive - we've had it when printing messages nested, as format strings to thiserror etc. It is the bug we seem to make every single time. I appreciate compatibility constraints might be hard, but switching the two (or even making them both the same) would be easier to use.

[link2xt]

Related issue: dtolnay/thiserror#98

But I like this proposal to fix anyhow instead.

[Hocuri]

What about a feature flag that makes {} behave the same as {:#}? Would this be possible?

[link2xt]

Features are enabled when at least one dependency enables it, so they should not be used for "options". Otherwise pulling in a dependency which uses this "feature" will enable it for you and break your code and code of other dependencies which do not expect it.