Don't panic, return error

I think the following error is not user-friendly.

$ RUST_BACKTRACE=1 cargo run install hoge
    Finished dev [unoptimized + debuginfo] target(s) in 0.03s
     Running `target/debug/frum install hoge`
thread 'main' panicked at 'internal error: entered unreachable code', src/version.rs:33:13
stack backtrace:
   0: rust_begin_unwind
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b/library/core/src/panicking.rs:50:5
   3: frum::version::Version::parse
             at ./src/version.rs:33:13
   4: <frum::input_version::InputVersion as core::str::traits::FromStr>::from_str
             at ./src/input_version.rs:47:15
   5: frum::main::{{closure}}
             at ./src/main.rs:58:21
   6: core::option::Option<T>::map
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b/library/core/src/option.rs:823:29
   7: frum::main
             at ./src/main.rs:57:26
   8: core::ops::function::FnOnce::call_once
             at /rustc/c8dfcfe046a7680554bf4eb612bad840e7631c4b/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

I found at least two not-good points of error handling of this repository.

Version.parse() panics. This should return an error if the parse failed.
Dispatch of command uses expect(). Here, we should receive errors and show them to users.

I recommend you to use eyre and color-eyre. See https://github.com/yaahc/color-eyre/blob/master/examples/usage.rs and try to run. (eyre is a fork of anyhow and I think eyre suits CLI programs because it has additional features like suggestion.)

TaKO8Ki / frum

Don't panic, return error #103