Help with reducing subscription data with @urql/vue

[lewebsimple]

Hello,

I'm having a hard time understanding the subscription handler types in @urql/vue when trying to reduce the data as described in the documentation.

Let's say I have the following subscription in the schema:

type Subscription {
  pong: String!
}

Which I invoke like so:

const result = useSubscription(
    {
      query: graphql(`
        subscription Pong {
          pong
        }
      `),
    },
    handlePong, // see below
  );

I would expect result.data to be of type Ref<string[]> and handlePong to look like this:

function handlePong( prev = [], data ) {
  return [data.pong, ...(prev || [])]
}

But it seems the subscription handler expects (prev: string | undefined, data: string) => string.

What am I missing ???