fix(modelql): ClassCastException in .mapIfNotNull

fixes MODELIX-552

Author: slisson

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/IfEmpty.kt

@@ -26,7 +26,7 @@ class IfEmptyStep<In : Out, Out>(val alternative: UnboundQuery<Unit, *, Out>) :
     override fun createFlow(input: StepFlow<In>, context: IFlowInstantiationContext): StepFlow<Out> {
         val downCastedInput: StepFlow<Out> = input
         return downCastedInput.map { MultiplexedOutput(0, it) }.onEmpty {
-            emitAll(alternative.asFlow(context.evaluationContext, Unit).map { MultiplexedOutput(1, it) })
+            emitAll(alternative.asFlow(context.evaluationContext, Unit.asStepOutput(null)).map { MultiplexedOutput(1, it) })
         }
     }
 

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/MapIfNotNullStep.kt

@@ -32,9 +32,9 @@ class MapIfNotNullStep<In : Any, Out>(val query: MonoUnboundQuery<In, Out>) : Mo
     }
 
     override fun createFlow(input: StepFlow<In?>, context: IFlowInstantiationContext): StepFlow<Out?> {
-        return input.flatMapConcat {
-            it.value?.let { query.asFlow(context.evaluationContext, it).map { MultiplexedOutput(1, it) } }
-                ?: flowOf(MultiplexedOutput(0, it as IStepOutput<Out?>))
+        return input.flatMapConcat { stepOutput ->
+            stepOutput.value?.let { query.asFlow(context.evaluationContext, stepOutput.upcast()).map { MultiplexedOutput(1, it) } }
+                ?: flowOf(MultiplexedOutput(0, stepOutput.upcast()))
         }
     }
 

modelql-core/src/commonMain/kotlin/org/modelix/modelql/core/Query.kt

@@ -37,7 +37,7 @@ interface IQueryExecutor<out In> {
 
 class SimpleQueryExecutor<E>(val input: E) : IQueryExecutor<E> {
     override fun <ElementOut> createFlow(query: IUnboundQuery<E, *, ElementOut>): StepFlow<ElementOut> {
-        return query.asFlow(QueryEvaluationContext.EMPTY, input)
+        return query.asFlow(QueryEvaluationContext.EMPTY, input.asStepOutput(null))
     }
 }
 
@@ -105,9 +105,8 @@ private class FluxBoundQuery<In, Out>(executor: IQueryExecutor<In>, override val
 
 interface IUnboundQuery<in In, out AggregationOut, out ElementOut> {
     val reference: IQueryReference<IUnboundQuery<In, AggregationOut, ElementOut>>
-    suspend fun execute(evaluationContext: QueryEvaluationContext, input: In): IStepOutput<AggregationOut>
+    suspend fun execute(evaluationContext: QueryEvaluationContext, input: IStepOutput<In>): IStepOutput<AggregationOut>
     fun asFlow(evaluationContext: QueryEvaluationContext, input: StepFlow<In>): StepFlow<ElementOut>
-    fun asFlow(evaluationContext: QueryEvaluationContext, input: In): StepFlow<ElementOut> = asFlow(evaluationContext, flowOf(input).asStepFlow(null))
     fun asFlow(evaluationContext: QueryEvaluationContext, input: IStepOutput<In>): StepFlow<ElementOut> = asFlow(evaluationContext, flowOf(input))
     fun asSequence(evaluationContext: QueryEvaluationContext, input: Sequence<In>): Sequence<ElementOut>
 
@@ -165,7 +164,7 @@ class MonoUnboundQuery<In, ElementOut>(
 
     override fun bind(executor: IQueryExecutor<In>): IMonoQuery<ElementOut> = MonoBoundQuery(executor, this)
 
-    override suspend fun execute(evaluationContext: QueryEvaluationContext, input: In): IStepOutput<ElementOut> {
+    override suspend fun execute(evaluationContext: QueryEvaluationContext, input: IStepOutput<In>): IStepOutput<ElementOut> {
         try {
             return asFlow(evaluationContext, input).single()
         } catch (ex: NoSuchElementException) {
@@ -212,7 +211,7 @@ class FluxUnboundQuery<In, ElementOut>(
 
     override fun bind(executor: IQueryExecutor<In>): IFluxQuery<ElementOut> = FluxBoundQuery(executor, this)
 
-    override suspend fun execute(evaluationContext: QueryEvaluationContext, input: In): IStepOutput<List<IStepOutput<ElementOut>>> {
+    override suspend fun execute(evaluationContext: QueryEvaluationContext, input: IStepOutput<In>): IStepOutput<List<IStepOutput<ElementOut>>> {
         return asFlow(evaluationContext, input).toList().asStepOutput(null)
     }
 

modelql-core/src/commonTest/kotlin/org/modelix/modelql/core/ModelQLTest.kt

@@ -329,6 +329,14 @@ class ModelQLTest {
         assertEquals(testDatabase.products, result)
     }
 
+    @Test
+    fun mapIfNotNull() = runTestWithTimeout {
+        val result = remoteProductDatabaseQuery { db ->
+            "a".asMono().mapIfNotNull { it.identity() }.mapIfNotNull { it.identity() }
+        }
+        assertEquals("a", result)
+    }
+
     @Test
     fun zipElementAccess() = runTestWithTimeout {
         val result = remoteProductDatabaseQuery { db ->
@@ -385,7 +393,7 @@ suspend fun <ResultT> doRemoteProductDatabaseQuery(body: (IMonoStep<ProductDatab
     val deserializedQuery = json.decodeFromString<QueryGraphDescriptor>(serializedQuery).createRootQuery() as MonoUnboundQuery<ProductDatabase, ResultT>
     println("original query    : $query")
     println("deserialized query: $deserializedQuery")
-    val remoteResult: IStepOutput<ResultT> = deserializedQuery.execute(QueryEvaluationContext.EMPTY, testDatabase)
+    val remoteResult: IStepOutput<ResultT> = deserializedQuery.execute(QueryEvaluationContext.EMPTY, testDatabase.asStepOutput(null))
     val serializedResult = json.encodeToString(deserializedQuery.getAggregationOutputSerializer(json.serializersModule), remoteResult)
 //    println(serializedResult)
     return json.decodeFromString(query.getAggregationOutputSerializer(json.serializersModule), serializedResult).value