`anyhow::Error::to_string` doesn't print the full context

[emilk]

This has bitten us many times. That's why we have re_error::format.

• anyhow has no intention of changing this behavior: https://discord.com/channels/1062300748202921994/1373859622443548803/1373859622443548803
• eyre has the same problem: https://github.com/eyre-rs/eyre/issues/234

[wyfo]

According to https://github.com/dtolnay/anyhow/issues/85, using format!("{err:#}") instead of err.to_string() prints the whole context.

let err = anyhow::format_err!("root_cause")
    .context("inner_context")
    .context("outer_context");

assert_eq!(
    format!("{:#}", err),
    "outer_context: inner_context: root_cause"
);

[grtlr]

Another place where disallowed trait methods would be super useful:

• https://github.com/rust-lang/rust-clippy/issues/15765

Is there an open source bounty program for such things?