e7h4n / ccstate / 15699879880

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refactor: better promise rejection handling

## Why

consider the following case:

``` typescript
const promise$ = computed((get) => {
  return new Promise((_, reject) => {
    reject(new Error())
  })
});

const store = createStore();
store.sub(
  promise$,
  command(() => void 0),
);
```

The `sub` command will evaluate the promise$ once, and if the generated promise is rejected in this evaluation, there is no opportunity in this code to handle this rejection.

## How to Solve This Problem

In this commit, the `sub` command will attach a catch callback to the Promise returned by `computed` to handle exceptions. This does not mean that external access to the promise's exception will be blocked; the promise returned externally still contains the exception. This only prevents the global unhandledRejection.

This handling strategy is similar to preact-signals. https://stackblitz.com/edit/vitejs-vite-i8u9jc24?file=src%2Fpreact-promise.test.ts%3AL36

Co-authored-by: Yuchen Zhang <zhangyc@kanyun.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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