feat: Treat withState actions as side effects

Fixes #29. This change changes the treatment of GetStateActions.
These actions are now treated as side effects, and the state processor
does not wait for their completion. Instead, it spins off a separate
to execute them, and moves on to process other actions in the queue
without waiting for it to finish.

build.gradle

@@ -5,8 +5,8 @@ buildscript {
             "targetSdk"  : 29,
             "kotlin"     : "1.3.61",
             "agp"        : "3.5.2",
-            "versionCode": 11,
-            "versionName": "0.5.5"
+            "versionCode": 12,
+            "versionName": "0.6.0"
     ]
 
     ext.versions = [

vector/src/main/java/com/haroldadmin/vector/VectorViewModel.kt

@@ -79,7 +79,10 @@ abstract class VectorViewModel<S : VectorState>(
     /**
      * Dispatch the given action the [stateStore]. This action shall be processed as soon as all existing
      * state reducers have been processed. The state parameter supplied to this action should be the
-     * latest value at the time of processing of this action
+     * latest value at the time of processing of this action.
+     *
+     * These actions are treated as side effects. A new coroutine is launched for each such action, so that the state
+     * processor does not get blocked if a particular action takes too long to finish.
      *
      * @param action The action to be performed with the current state
      *

vector/src/main/java/com/haroldadmin/vector/state/SelectBasedStateProcessor.kt

@@ -91,7 +91,9 @@ internal class SelectBasedStateProcessor<S : VectorState>(
                     stateHolder.stateObservable.offer(newState)
                 }
                 getStateChannel.onReceive { action ->
-                    action.invoke(stateHolder.state)
+                    launch {
+                        action.invoke(stateHolder.state)
+                    }
                 }
             }
         }

vector/src/main/java/com/haroldadmin/vector/state/StateProcessor.kt

@@ -37,16 +37,20 @@ interface StateProcessor<S : VectorState> : CoroutineScope {
 
     /**
      * Offer a [SetStateAction] to this processor. This action will be processed as soon as
-     * possible, before all existing [GetStateAction], if any.
+     * possible, before all existing [GetStateAction] waiting in the queue, if any.
      *
      * @param reducer The action to be offered
      */
     fun offerSetAction(reducer: suspend S.() -> S)
 
     /**
-     * Offer a [GetStateAction] to this processor. This action will be processed after any existing
-     * [GetStateAction] current waiting in this processor. The state parameter supplied to this action
+     * Offer a [GetStateAction] to this processor. The state parameter supplied to this action
      * shall be the latest state value at the time of processing this action.
+     *
+     * These actions are treated as side effects. When such an action is received, a separate coroutine is launched
+     * to process it. This means that when there are multiple such actions waiting in the queue, they will be launched
+     * in order, but their completion depends on how long it takes to process them. They will be processed in the
+     * coroutine context of their state processor.
      */
     fun offerGetAction(action: suspend (S) -> Unit)
 

vector/src/test/java/com/haroldadmin/vector/state/SelectBasedStateProcessorTest.kt

@@ -1,5 +1,6 @@
 package com.haroldadmin.vector.state
 
+import com.haroldadmin.vector.Vector
 import com.haroldadmin.vector.extensions.awaitCompletion
 import com.haroldadmin.vector.loggers.systemOutLogger
 import kotlinx.coroutines.CompletableDeferred
@@ -8,6 +9,7 @@ import kotlinx.coroutines.Job
 import kotlinx.coroutines.async
 import kotlinx.coroutines.awaitAll
 import kotlinx.coroutines.channels.ClosedSendChannelException
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.runBlocking
 import org.junit.After
 import org.junit.Before
@@ -21,7 +23,12 @@ internal class SelectBasedStateProcessorTest {
     @Before
     fun setup() {
         holder = StateHolderFactory.create(CountingState(), systemOutLogger())
-        processor = SelectBasedStateProcessor(true, holder, systemOutLogger(), Dispatchers.Default + Job())
+        processor = SelectBasedStateProcessor(
+            isLazy = true,
+            stateHolder = holder,
+            logger = systemOutLogger(),
+            coroutineContext = Dispatchers.Unconfined + Job()
+        )
     }
 
     @After
@@ -109,7 +116,12 @@ internal class SelectBasedStateProcessorTest {
 
         processor.start()
 
-        awaitAll(incrementActionsSourceJob, decrementActionsSourceJob, additionJobsCompletable, subtractionJobsCompletable)
+        awaitAll(
+            incrementActionsSourceJob,
+            decrementActionsSourceJob,
+            additionJobsCompletable,
+            subtractionJobsCompletable
+        )
 
         assert(holder.state.count == 0)
     }
@@ -126,4 +138,24 @@ internal class SelectBasedStateProcessorTest {
         processor.start()
         repeat(10) { processor.clearProcessor() }
     }
+
+    @Test
+    fun `should not wait for get-state actions to complete before processing the next action`() = runBlocking {
+        val initialCount = holder.state.count + 1
+        processor.start()
+
+        processor.offerGetAction {
+            delay(1000L)
+        }
+
+        awaitCompletion<Unit> {
+            processor.offerSetAction {
+                copy(count = initialCount + 1).also { complete(Unit) }
+            }
+        }
+
+        assert(holder.state.count == initialCount + 1) {
+            "Expected count = ${initialCount + 1}, actual: ${holder.state.count}"
+        }
+    }
 }