decide on `onSetLanguageTag` throwing or not approach

[samuelstroschein]

Problem

Paraglide's strictness for "setting" the onSetLanguageTag callback is causing HMR issues.

• https://github.com/inlang/monorepo/issues/1686
• https://github.com/inlang/monorepo/discussions/1464#discussioncomment-7338784

[samuelstroschein]

Not changing the behavior atm. Throwing is OK because changing to not throwing is not a breaking change. Changing the behavior from not throwing to throwing would be a breaking change however.

[samuelstroschein]

Given that users run into this problem all the time, it is probably best to remove the strictness/throw. @LorisSigrist what do you think?

[LorisSigrist]

Yes I agree we need to be more permissive here. The question is how. Do we just allow many subscriptions to the language tag? What was the reasoning behind not doing that up until now?

[samuelstroschein]

Do we just allow many subscriptions to the language tag?

No subscriptions. Complexity for no value. Triggering multiple side-effects with different calls to onSetLanguageTag will a) lead to unexpected behavior b) memory leaks if the subscriptions are not disposed and c) everything can be handled in one call anyways.

I would simply not throw, let people re-assign the callback and warn in the docs that onSetLanguageTag will always be reassigned and cannot be set multiple times.

[LorisSigrist]

That makes sense. Should we also console.warn when a callback get's overridden?

[samuelstroschein]

Should we also console.warn when a callback get's overridden?

Could be super annoying in HMR.

We can also evaluate whether the bundler plugins resolve the HMR issue and not loosen the strictness of throwing. Having an explicit throw seems better than a warning hidden in the docs or console. Except ofc if HMR sets the callback but that can be avoided with bundler adapters.

If we expect everyone who uses bundlers to choose one of our adapters, we should be able to circumvent the issue of throws in HMR without loosening the strictness/immediate feedback "you can't set onSetLanguageTag multiple times".

@LorisSigrist can you explore in #1669 whether you can fix the HMR issues in those adapters? If you fix it in adapters, we need tests for it ;)

[LorisSigrist]

I'll see if I can make that happen!

[LorisSigrist]

@samuelstroschein We need to re-discuss this.

I have been able to reproduce the HMR issues thanks to @KraXen72. They only happen if the callback isn't inlined. In order for HMR to work, it needs to be able to reassign the callback. We can't make this work in the adapters like we thought.

I'll reopen #1699

[samuelstroschein]

@LorisSigrist that's what I thought. Okay, reassigning it is. I hope that we don't trigger regression bugs/unexpected behavior.