KT.SUSPEND_FUN_WITH_FLOW_RETURN_TYPE

Functions that return Flow from 'kotlinx.coroutines.flow' are marked as suspend

Functions that return Flow from kotlinx.coroutines.flow should not be marked as suspend. Flows are intended to be cold observable streams. The act of simply invoking a function that returns a Flow, should not have any side effects. Only once collection begins against the returned Flow, should work actually be done. See https://kotlinlang.org/docs/flow.html#flows-are-cold

Noncompliant Code

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suspend fun observeSignals(): Flow<Unit> {
    val pollingInterval = getPollingInterval() // Done outside of the flow builder block.
    return flow {
        while (true) {
            delay(pollingInterval)
            emit(Unit)
        }
    }
}

private suspend fun getPollingInterval(): Long {
    // Return the polling interval from some repository
    // in a suspending manner.
}

Compliant Code

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fun observeSignals(): Flow<Unit> {
    return flow {
        val pollingInterval = getPollingInterval() // Moved into the flow builder block.
        while (true) {
            delay(pollingInterval)
            emit(Unit)
        }
    }
}

private suspend fun getPollingInterval(): Long {
    // Return the polling interval from some repository
    // in a suspending manner.
}