js2-mode does not recognize asynchronous generators within class or object

[belden]

js2-mode struggles with this code. async *... within class context seems not to be recognized. The parsed function ends up not being set as async, which means the await is incorrectly flagged as occurring within a non-async function ("msg.bad.await").

#!/usr/bin/env node

class Toy {
  // (1) `async` not detected correctly
  // (2) `*` not treated correctly
  // (3) `await` treated as "msg.bad.await"

  async *oneByOne() {
    const resp = await this.getRecords();
    for (const rec of resp.records) {
      yield rec;
    }
  }

  // `async` / `await` have no parsing errors here
  async getRecords() {
    const out = await Promise.resolve({ records: [1, 2, 3] });
    return out;
  }

  // `*` treated correctly here
  *correctGeneratorDetection() {
    for (const r of [1, 2, 3]) {
      yield r;
    }
  }
}

(async () => {
  const toy = new Toy();
  for await (const rec of toy.oneByOne()) {
    console.log(rec);
  }
})();

There's also a superflous complaint from the code above that the * at *all requires a colon ("msg.no.colon.prop").

📸 click here to see screenshot


---

Similar, but not identical, parsing errors occur when converting the above code to a simple object. In this next example, the * in *all still shows an error ("msg.no.colon.prop"). The function is not recognized as a generator though, since yield also shows an error ("msg.bad.yield").

#!/usr/bin/env node

const obj = {
  // (1) `async` not detected correctly
  // (2) `*` not treated correctly (error: "msg.no.colon.prop")
  // (3) `yield` treated as an error (error: "msg.bad.yield")

  async *all() {
    const resp = await getRecords();
    for (const rec of resp.records) {
      yield rec;
    }
  }
};

// (4) generic "syntax error" (error: "msg.syntax")

async function getRecords() {
  return Promise.resolve({ records: [1, 2, 3] });
}

(async () => {
  for await (const rec of obj.all()) {
    console.log(rec);
  }
})();

📸 click here to see screenshot


---

In both cases, both pieces of code really do run, and simply log 1\n2\n3\n.

---

My environment:

• node version: 14, 16, 18
• js2-mode version: 20230408 (specifically, a fresh clone of this repo, with HEAD at 79bc78d)
• GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, cairo version 1.16.0) of 2023-11-27

[dgutov]

Hi!

Thanks for the excellent report, both cases should work now.

[belden]

@dgutov Thanks for the fast fix! Indeed, both toy scripts render correctly now.

[dgutov]

Thanks for checking. I've tagged a new release too, so that the fix is out to stable channels.