Skip Attribute

[la10736]

Attributes are evolving and now are used also to create DSL. Now, by the rising of procedural macro and the possibility to use arbitrary rust code in attributes syntax formatting attribute by simple rules based on meta and nested meta can produce some formatting that make the procedural macro DSL not clear.

For instance I have a crate of mine la10736/rstest that you can use to write tests like this:

#[rstest_parametrize(foo, bar, baz,
    case(0, "a", "A"),
    case(1, "b", "B")
)]
fn mytest(foo: u32, bar: &str, baz: &str) {}

Now, use rustfmt on this file make it flat and hard to read:

#[rstest_parametrize(foo, bar, baz, case(0, 'a', 'A'), case(1, 'b', 'B'))]
fn mytest(foo: u32, bar: char, baz: char) {}

Or wrost:

#[rstest_parametrize(foo, bar, baz,
    case(0, "a", "Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
    case(1, "b", "B")
)]
fn mytest(foo: u32, bar: &str, baz: &str) {}

in

#[rstest_parametrize(
    foo, 
    bar,
    baz,
    case(0, "a", "Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
    case(1, "b", "B")
)]
fn mytest(foo: u32, bar: &str, baz: &str) {}

We can use rustfmt::skip::macros() or a brand new rustfmt::skip::attributes() to have the ability of skip attributes formatting too.

If you are ok I can work on it.

[topecongiro]

It seems like a good idea given that, like macro calls, attributes can have an arbitral token stream as their arguments.

[topecongiro]

Adding a new rustfmt::skip::attributes() seems better to me.

[la10736]

I'm done with base implementation but is just a cut and paste of rustfmt::skip::macros() implementation. I tempted to refactor all skip's stuff before submit but I should decide if merge just macros and attributes stuffs or encapsulate rustfmt::skip responsibility too.

The second one solution touch lot of files so maybe is better do a separate pull request but merge just sub attributes left things less cohesive.

What do you think?

[scampi]

@la10736 a separate PR would probably be better

[la10736]

I already did the PR with just refactoring macros and attributes. I left rustfmt::skip's stuff untouched.