Hi there mates! QQ about `CompositionLocal`s

# compose

[xoangon]

Hi there mates! QQ about `CompositionLocal`s

[xoangon]

We're using `CompositionLocal`s to set our app theme. Our app is using both Views and Compose and we're using AbstractComposeView in a lot of places, thus having more than one call to setContent.

The thing is, if we forget to set the `CompositionLocal`s in any of those, we end up with a crash at runtime with a stack trace that's way far from explicit (full stack trace in this Google Issue Tracker report)

I'd like to hook into any call to setContent and provide a meaningful error if those implicit dependencies are not provided. Is there a way to do this?

If that's not feasible, I may consider some type of lint

[Stylianos Gakis]

What you get by default from a CL is defined by you right? You could definitely have something like

internal val Foo = staticCompositionLocalOf<Foo> {
  error("Foo not provided")
}

Would that be sufficient for you here?

[xoangon]

That seems to be what I was looking for! On my way to test that out

[Stylianos Gakis]

You could also consider not crashing in production but providing a sane default (as material3 color scheme does with light color scheme for example) but still log a high severity warning.

[xoangon]

The snippet above is what I was looking for, thanks!

[xoangon]

I used to do super-defensive programming with no errors at runtime at my previous company and were I am right now we do offensive programming with development under feature-flag.

I was a bit shocked at first, but by providing meaningful errors and having an easy roll-back setup, I'm amazed by the time saved! Opposite to what I was expecting, our app ends up being more robust as we realise early when something's not working well instead of having a ton of users falling in undesired weird states with missing information

[Stylianos Gakis]

Yep, as long as you got an easy way to roll back that is 😅

[xoangon]

Yup, it would be crazy without that 🤣

[myanmarking]

If it is a developer error, crash always. Going otherwise is making it worst