Calling `execProtocol` when PGlite is not ready

[jgoux]

Hey, it's me again. 😄

execProtocol is not checking if the database is ready, which triggers this error when called externally to send wire protocol messages:

TypeError: undefined is not an object (evaluating 'this.emp._malloc')

I see 3 solutions:

• Calling await this.#checkReady(); in the execProtocol function
• Keeping execProtocol as is for internal use within PGlite but exposing a version with await this.#checkReady(); applied
• Making PGlite extends EventEmitter and emits a ready event when ready (my favorite solution)

In the end, I think execProtocol is exposed for low-level implementations such as pglite-server so I wouldn't do extra work in execProtocol.

[samwillis]

Adding note here for others after we chatted on Discord here: https://discord.com/channels/933657521581858818/1212676471588520006/1225898205292793928

Good idea on making PGlite an EventEmitter, we should do that, and it's needed for when we support pg_notify.

It's currently possible to await pg.waitReady, this is a promise that resolves at the end of the init. We can't wait for that inside execProtocol as execProtocol is itself used inside the init and that would result in a deadlock.

I've purposely not documented execProtocol yet as I want feedback on its design, and whats the best way for it to work for the server simulation use case.

We could have public and privet versions of execProtocol, an internal one without waitRead and a public one with it.

[jgoux]

I missed waitReady! For now, it's more than enough for my use case. 👍