Support crate attribute in proc-macro wasm_bindgen_test

[FirelightFlagboy]

Motivation

We have multiple crates that we would like to test using wasm-bindgen-test.

For the ease-of-use on our side we create a proc-macro that wrap multiple other proc-macro (rstest, tokio::test, custom testbed) for testing.

To use that proc-macro the developer would have to import (add as a dependency) a single crate that provide the proc-macro + re-export rstest, tokio::test and testbed.

But to support wasm-bindgen-test we're required to alongside the test crate to also import wasm-bindgen-test and we would like to have it re-exported in the test crate instead.

Currently wasm-bindgen-test proc macro use a fixed path to the crate wasm_bindgen_test (cf the generated function by the proc-macro wasm_bindgen_test

#[no_mangle]
pub extern "C" fn __wbgt_case_1_invalid_type_deserialization_2(
    cx: &::wasm_bindgen_test::__rt::Context,
) {
    let test_name = "misc::serde_invalid_type_deserialization::case_1_invalid_type_deserialization";
    cx.execute_sync(test_name, case_1_invalid_type_deserialization, None);
}

Proposed Solution

A solution would be to do something like tokio::test handle renaming the crate with the crate attribute provided to the proc-macro.

A clear and concise description of the feature you would like to add, and how it solves the motivating problem.

Alternatives

An alternative would have to add wasm-bindgen-test to each of our crates that will be tested with it.
For the easy-of-use we would have preferred to import a single crate that re-expose those utility crates.

Additional Context

This feature will required to:

• Handle a new token here:

  wasm-bindgen/crates/test-macro/src/lib.rs

  Lines 23 to 31 in 86fd961

  	match &token {
  	proc_macro::TokenTree::Ident(i) if i.to_string() == "async" => r#async = true,
  	_ => {
  	return compile_error(
  	token.span().into(),
  	"malformed `#[wasm_bindgen_test]` attribute",
  	)
  	}
  	}

• Tweak the generated function at

  wasm-bindgen/crates/test-macro/src/lib.rs

  Line 99 in 86fd961

  pub extern "C" fn #name(cx: &::wasm_bindgen_test::__rt::Context) {

[daxpedda]

I have done this for the wasm_bindgen macro here: #3360.
Happy to review a PR implementing this for wasm_bindgen_test as well!

[FirelightFlagboy]

I've create a PR (#3593)