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kotlinlang

Hi ! I have a design problem with `Flow`. I have a source flow the emits the current result of a request in database whenever it changes (like a `Flow` returned by Android Room). I decided to expose the result of those request with a repository.

```interface DataSource {
    val flow: Flow&lt;List&lt;Foo&gt;&gt;
}

class Repository(
    private val source: DataSource
)
    val diff: Flow&lt;Diff&lt;Foo&gt;&gt; get() = TODO()
    suspend fun getLatest(): List&lt;Foo&gt; = TODO()
}```
How can I transform the source flow to adapt it to the needs of the `Repository` ? (The `Diff` is calculated from the latest and the previous list of `Foo`s.)
Is it possible to cache the latest value just like Android `LiveData`, to avoid costly database queries when repeateadly reading the latest values ?

<https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/conflate.html> ?

The `conflate` operator may be part of the solution, but it does not cache the latest value, each call to `getLatest()` still triggers a database query

There is no direct Flwo analogue of BehaviorSubject/LiveData. It in development now (there is a PR, search for DataFlow)

But you can use ConflatedBroadcastChannel in coroutines, there is asFlow() extension, so you can expose such channel as Flow

Good to know ! I'm very enthousiastic about that DataFlow . <@U0BRK9HC5> Do you know how it behaves in case of an exception in the upstream ?
In my case, the source flow throws a specific exception if some permission is not denied. Will `DataFlow` rethrow that exception or re-collect the upstream ? I'd really like option 2.

But DataFlow or ConflatedBroadcastChannel do not have upstream, that is the whole point