[v6] FetchCancelSignal might have an incorrect assertion

[hzhu]

Ethers Version

6.0.0

Search Terms

provider

Describe the Problem

Hi! Thank you for shipping V6 🥳. Before I submit a pull request, I wanted to confirm if my understanding of the issue is correct. The provider is unable to fetch:

const RPC_URL = "https://eth-mainnet.g.alchemy.com/v2/<API-KEY>";
const provider = new JsonRpcProvider(RPC_URL);
const network = await provider.getNetwork(); // can't fetch network 😢 

✅ Minimal CodeSandbox demo in v5 (working)

❌ Minimal CodeSandbox demo in v6 (not working)

The error

Error: signal already cancelled (operation="fetchCancelSignal.addCancelListener", code=UNSUPPORTED_OPERATION, version=6.0.0)

I tested this locally and received an assertion error from utils/fetch.ts claiming that the signal was cancelled, however it wasn't (this.#cancelled was set to false).

It's coming from the assertion in addListener:

addListener(listener) {
  assert$1(this.#cancelled, "singal already cancelled", "UNSUPPORTED_OPERATION", {
    operation: "fetchCancelSignal.addCancelListener"
  });
  this.#listeners.push(listener);
}

The solution

As the assert function inverts the check boolean internally, perhaps it should be rewritten in this manner:

addListener(listener) {
  if (this.#cancelled) {
    assert$1(false, "signal already cancelled", "UNSUPPORTED_OPERATION", {
        operation: "fetchCancelSignal.addCancelListener"
    });
  } else {
    this.#listeners.push(listener);
  }
}

Here's a live demo of the solution. Here's a CodeSandbox demo of the solution in practice. I copied Ethers v6 from Cloudflare CDN to a local file and adjusted the addListener function based on the solution mentioned above.

Code Snippet

No response

Contract ABI

No response

Errors

Error: signal already cancelled (operation="fetchCancelSignal.addCancelListener", code=UNSUPPORTED_OPERATION, version=6.0.0)

The "listener" argument must be of type Function. Received type object

Environment

Browser (Chrome, Safari, etc)

Environment (Other)

No response

[ricmoo]

Ack! I switched a bunch of if (blah) throw to assert(!blah) and missed some of the negations. I thought I’d caught them all, but might have missed this one.

I’ll get to this right away. Thanks!

[ricmoo]

So, the signal being crossed is definitely a bug, but not one that should be affecting your above code.

I am able to use your code to get back Network object...

[ricmoo]

Oh!! Maybe because you are in the browser? Which uses a different geturl function, which does use the Signal.

Ok... I'll make the change and push it out, because it is certainly a bug. :)

[ricmoo]

This should be fixed in v6.0.2. Try it out and let me know! :)

This is also extra incentive to get the Karma tests back up an running, to help detect the browser-specific issues.

Thanks! :)

[hzhu]

It's working now! Your fix was incredibly fast and I am so grateful. Thank you so much @ricmoo!