Suggestion for a beginner's crate

help
1

Hi all.
For study I have to create my own crate, but although long researching I've got no idea. I've been programming RUST for half a year, so I'd call myself an advanced beginner. Has anyone got an idea or a wish for a crate I could develop?

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2

What a coincidence! I just had an idea for a small crate yesterday! would have implemented it myself if I haven't had other projects to maintain :slight_smile:

Some of my functions return rather elaborate structs like

struct Foo {
   bar: Bar
   bazes: Vec<Baz>
}

When testing such functions, I need to compare that the result is what I wanted to get. However, constructing such functions by hand is hard. So what I do is the following:

let foo = function_under_test();
assert_eq!(
    format!("{:?}", foo),
    r#"here I write Foo's debug representation"#
)

This approach has a couple of drawbacks:

  1. Debug string is white space sensitive, it can get pretty large and I can't split it over several lines or indent it
  2. I can't get a nice report about what exactly was different.

I think this can be handled with a function of the following signature:

fn assert_ron<T: Serialize>(actual: T, expected: &str) {
    let actual_ron = serialize_to_ron(actual);
    let expected_ron = parse_ron(expected);
    smart_diff_rons(actual_ron, expected_ron);
}

Where expected is a string with ron notation.

The call site might look like this:

assert_ron(get_scene(), r#"
Scene(
    materials: {
        "metal": (
            reflectivity: 1.0,
        ),
        "plastic": (
            reflectivity: 0.5,
        ),
    },
    entities: [
        (
            name: "hero",
            material: "metal",
        ),
        (
            name: "monster",
            material: "plastic",
        ),
    ],
)
"#)

And the result might look like this

mismatch in entities[0].name.

Expected: `"hero"`
Got: "villain"

I've even written something similar for Cargo, there's a function which finds mismatch in JSON objects:
https://github.com/rust-lang/cargo/blob/f6ef6349b18f70243428aefd122edda80da7dab1/tests/cargotest/support/mod.rs#L642

1 Like
3

Thanks for your suggestion, this idea sounds interesting.
But what do you think: what size will this crate have?
I understand that the functions serialize_to_ron(actual) and parse_ron(expected) already exist. So the only thing to do would be smart_diff_rons(actual_ron, expected_ron), wouldn't it?
The point is: this study project is planned to be finished within a time of 5 weeks. So do you (or any other user) have any further suggestions for expansion of this crate, so that it will be enough work for 5 weeks?

Thank you in advance