Better panic handling

[mattgodbolt]

I'm not sure what the rust-y way to do this is but when I typo a timezone, this seems pretty nasty:

$ rizzy --zone not_a_tz
thread 'main' panicked at 'Could not parse timezone: not_a_tz, Error: 'not_a_tz' is not a valid timezone', src/main.rs:45:19
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[siedentop]

Hi @mattgodbolt ,

I hacked together a solution with autocomplete. What do you think of the following output?

chris@christophs-air rizzy % cargo run -- -z America/Chi
    Finished dev [unoptimized + debuginfo] target(s) in 0.07s
     Running `target/debug/rizzy -z America/Chi`
Error: 
   0: Unknown timezone 'America/Chi', did you mean: ["America/Chihuahua", "America/Chicago"]

Location:
   src/main.rs:103

Backtrace omitted.
Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

1. Demo draft is here, but would require for Make TIMEZONES map public, so that users may iterate over all timezones. chronotope/chrono-tz#95 to be merged (in some form or another). Timezones: Build auto-suggestion from all known timezones. #12
2. My PR (Timezones: Build auto-suggestion from all known timezones. #12) only does the auto-suggestion and removes one panic!, but there's a few others that could be removed.

[mattgodbolt]

Thanks @siedentop !

I was wondering about maybe not panic-ing at all in these cases and handling it more user-friendlyly. This is a huge improvement of course, but as a user of a tool, I probably never want to see anything specific to the language a command-line tool was written in if I mistyped an option :-)

I love the autocomplete thing, and I guess I would imagine an ideal output is:

% cargo run -- -z America/Chi
    Finished dev [unoptimized + debuginfo] target(s) in 0.07s
     Running `target/debug/rizzy -z America/Chi`
Unknown timezone 'America/Chi', did you mean: ["America/Chihuahua", "America/Chicago"]
%

The rest is visual noise to the user (though handy if you are a developer). My sort of mental model is if you typed a bad command-line parameter to cat you get:

$ cat -f
cat: invalid option -- 'f'
Try 'cat --help' for more information.

and not something like

 cat -f
Error:
  0: invalid option -- 'f'

Location:
    src/cat.c:34

Backtrace omitted.
Run with DEBUG_.BINUTILS=1 environment variable to display it.
Run with DEBUG_BINUTILS=full to include source snippets.

(etc!)

I have this beef with plenty of Python tools that expose their innards to unsuspecting users if the user makes a mistake :)

[siedentop]

Yes, totally!

The answer to that is to use eprintln!("Rizzy failed on: {}", error);.

I'll add a patch in a day or so.

[siedentop]

I updated this. But the upstream library still has not had a response to my request to make the list of timezone names readable from the library.

[siedentop]

UPDATE: It looks like the upstream library (chrono-tz) is willing to merge my patch.