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Why is only `flow2` being called in `flow1.map{ flow2(it) }.flattenConcat()`? 

`flow1` is a `MutableStateFlow&lt;MutableSet&lt;Int&gt;&gt;` of db entity IDs, `flow2` is a Flow of lists of entities, which is updated when any of the flow's entities' properties change. I am updating the properties and then calling `flow1.emit(set)`, but only `flow2.onEach` is being called, not `flow1.map{}`. Any suggestions?

You mention `flow2.onEach` , but it's not clear how this is being used by `flow1.map{ flow2(it) }.flattenConcat()`.
Can you provide a more detailed/complete code sample?

If `flow2.onEach` is called, then `flow1.map` must have been called at least once.  Are you saying that you don't see execution of `flow1.map` when you call `flow1.emit` after the first time?  If so, is it possible that `flow2` is exerting backpressure?  If so, <https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/-state-flow/index.html|this> from the MutableStateFlow docs may be relevant:
```Updates to the value are always conflated. So a slow collector skips fast updates, but always collects the most recently emitted value.```
This would cause `emit`s to be ignored, and `map` would not execute for those dropped values.

I think it would be helpful if you provided some small code sample that demonstrates the issue, ideally one that’d run on <https://play.kotlinlang.org>