Improve the error message when trying to use OPFS outside of a worker

[TheAndrewJackson]

Description

I'm running into an issue when trying to create a new database using the OPFS AHP file system. This snippet

import { PGlite } from "@electric-sql/pglite";

const client = await PGlite.create({
  dataDir: "opfs-ahp://electric.db",
  relaxedDurability: true,
});

is producing this error

I have a minimal-repro repo here that has the issue: https://github.com/TheAndrewJackson/opfs-ahp_bug_repro

[AntonOfTheWoods]

https://pglite.dev/examples/opfs

It needs to be somewhere that allows the sync api, so in a web/service (shared?) worker.

[samwillis]

Thanks for the report @TheAndrewJackson

The OPFS AHP VFS only works in a dedicated web worker as it requires the sync access handle API which is not available on the main thread, in shared workers, or in service workers.

We should improve the error message on this.

[TheAndrewJackson]

ahh, that makes sense @samwillis. Thanks for the clarification!

[psh4607]

I opened draft PR #1079 to address this issue. It now detects when the synchronous access handle API is unavailable and reports a clear error explaining that OPFS-AHP requires a Dedicated Web Worker. The PR also includes regression tests and updates the documentation.
Feedback is welcome: #1079