Fix stack overflow error in AssembleModelGenerator.kt for arrays

Author: Alexey Menshutin

utbot-framework-api/src/main/kotlin/org/utbot/framework/plugin/api/Api.kt

@@ -420,7 +420,7 @@ data class UtArrayModel(
     override val id: Int,
     override val classId: ClassId,
     val length: Int = 0,
-    val constModel: UtModel,
+    var constModel: UtModel,
     val stores: MutableMap<Int, UtModel>
 ) : UtReferenceModel(id, classId) {
     override fun toString() = withToStringThreadLocalReentrancyGuard {

utbot-framework/src/main/kotlin/org/utbot/framework/assemble/AssembleModelGenerator.kt

@@ -195,19 +195,24 @@ class AssembleModelGenerator(private val methodUnderTest: UtMethod<*>) {
     /**
      * Assembles internal structure of [UtArrayModel].
      */
-    private fun assembleArrayModel(arrayModel: UtArrayModel): UtModel {
-        instantiatedModels[arrayModel]?.let { return it }
+    private fun assembleArrayModel(arrayModel: UtArrayModel): UtModel =
+        with(arrayModel) {
+            instantiatedModels[this]?.let { return it }
 
-        val constModel = assembleModel(arrayModel.constModel)
-        val stores = arrayModel.stores
-            .mapValues { assembleModel(it.value) }
-            .toMutableMap()
+            // Note that we use constModel from the source model as is here to avoid
+            // possible stack overflow error in case when const model has the same
+            // id as the source one. Later we will try to transform it.
+            val assembleModel = UtArrayModel(id, classId, length, constModel, stores = mutableMapOf())
 
-        val assembleModel = UtArrayModel(arrayModel.id, arrayModel.classId, arrayModel.length, constModel, stores)
+            instantiatedModels[this] = assembleModel
 
-        instantiatedModels[arrayModel] = assembleModel
-        return assembleModel
-    }
+            assembleModel.constModel = assembleModel(constModel)
+            assembleModel.stores += stores
+                .mapValues { assembleModel(it.value) }
+                .toMutableMap()
+
+            assembleModel
+        }
 
     /**
      * Assembles internal structure of [UtCompositeModel] if possible and handles assembling exceptions.

utbot-framework/src/test/kotlin/org/utbot/examples/arrays/ArrayOfArraysTest.kt

@@ -266,4 +266,14 @@ internal class ArrayOfArraysTest : AbstractTestCaseGeneratorTest(testClass = Arr
             { valueBefore, valueAfter -> valueAfter.withIndex().all { it.value == valueBefore[it.index] + it.index } }
         )
     }
+
+    @Test
+    fun testArrayWithItselfAnAsElement() {
+        check(
+            ArrayOfArrays::arrayWithItselfAnAsElement,
+            eq(2),
+            coverage = atLeast(percents = 94)
+            // because of the assumption
+        )
+    }
 }

utbot-sample/src/main/java/org/utbot/examples/arrays/ArrayOfArrays.java

@@ -152,4 +152,14 @@ public int[][] fillMultiArrayWithArray(int[] value) {
 
         return array;
     }
+
+    public Object[] arrayWithItselfAnAsElement(Object[] array) {
+        UtMock.assume(array != null && array.length > 0);
+
+        if (array[0] == array) {
+            return array;
+        }
+
+        return null;
+    }
 }