implemented Debug for Tag to print in hex

[ibaryshnikov]

Motivation: provide useful output for searching tag in dictionary.
Before println!("{:?}", tag) would print Tag(32736, 16), after: Tag(0x7FE0, 0x0010), and now it's easy to find E { tag: Tag(0x7FE0, 0x0010), alias: "PixelData"

[Enet4]

I wasn't quite expecting to receive PRs at this time, but this one is isolated enough for a quick review.

One can add those formatting flags at the upper level, to obtain a similar outcome:

println!("{:04X?}", tag); // Tag(7FE0, 0010)

What we can't do without a custom Debug implementation is to pretty-print the two components of the tag without pretty-printing the whole struct, so it doesn't add the 0x prefix without it. I also recall that the Display impl already provides a familiar formatting for tags: (GGGG, EEEE).

With this in mind, I'm reluctant to make this change, but would like to hear from you whether the methods above solve your particular concern. The standard dictionary should also be searchable at run-time by tag, so an exact textual match might not be needed.

[ibaryshnikov]

I did a lot of debugging recently while opening different files and found this addition quite useful. I don't insist of course, I can still patch it locally.
Usually I just do dbg!(). I like the idea with println!("{:04X?}, tag"), I'll try it and submit a feedback later. At first glance in playground:

#[derive(Debug)]
struct Tag(u16, u16);

#[derive(Debug)]
struct Data {
    tag: Tag,
    value: i32,
}

fn main() {
    let tag = Tag(0xFE00, 0xFFFF);
    println!("{:X?}", tag); // Tag(FE00, FFFF)
    let data = Data { tag, value: 123 }; // I'd like to see this `value` as a decimal
    println!("{:?}", data); // Data { tag: Tag(65024, 65535), value: 123 }
    println!("{:X?}", data); // Data { tag: Tag(FE00, FFFF), value: 7B }
    dbg!(&data);
    // [src/main.rs:24] &data = Data {
    // tag: Tag(
    //     65024,
    //     65535,
    // ),
    // value: 123,
}

[Enet4]

After some thinking and discussion with other Rust developers, I am willing to make an exception and accept the proposed change at this stage, considering that hexadecimal printing of tag components is indeed useful and more reasonable for this particular data type.

Please see the minor tweak suggested below before merging.

[ibaryshnikov]

I'm happy to hear that! And your suggestion looks clearer

[Enet4]

Looks good now, thanks!