Implement recursion guard for aggregate inspection

src/main/kotlin/org/axonframework/intellij/ide/plugin/resolving/AggregateStructureResolver.kt

@@ -97,13 +97,18 @@ class AggregateStructureResolver(private val project: Project) {
         .flatMap {
             AnnotatedElementsSearch.searchPsiClasses(it.psiClass, project.axonScope()).findAll()
         }
-        .mapNotNull { inspect(it, null) }
+        .mapNotNull { inspect(it, emptyList()) }
         .flatMap { it.flatten() }
 
-    private fun inspect(clazz: PsiClass, parent: PsiClass?): Entity? {
+    private fun inspect(clazz: PsiClass, parents: List<PsiClass>, depth: Int = 0): Entity? {
         if (clazz.isEnum) {
             return null
         }
+        if(parents.contains(clazz) || depth > 20) {
+            // Guard for infinite recursion; we already have this class indexed, or we exceed an exorbitant depth
+            return null
+        }
+        val parent = parents.lastOrNull()
         val children = clazz.fields.toList()
             .filter { it.isAnnotated(AxonAnnotation.AGGREGATE_MEMBER) }
             .mapNotNull { field ->
@@ -112,7 +117,7 @@ class AggregateStructureResolver(private val project: Project) {
                 val qualifiedName = psiType.toQualifiedName() ?: return@mapNotNull null
                 val targetClass = clazz.javaFacade().findClass(qualifiedName, clazz.project.axonScope())
                     ?: return@mapNotNull null
-                val modelMember = inspect(targetClass, clazz) ?: return@mapNotNull null
+                val modelMember = inspect(targetClass, parents + clazz, depth + 1) ?: return@mapNotNull null
                 val routingKey = field.resolveAnnotationStringValue(AxonAnnotation.AGGREGATE_MEMBER, "routingKey")
                 val eventForwardingMode = field.resolveAnnotationClassValue(AxonAnnotation.AGGREGATE_MEMBER, "eventForwardingMode")
                 EntityMember(field, field.name, modelMember, isCollection, routingKey, eventForwardingMode)

src/test/kotlin/org/axonframework/intellij/ide/plugin/markers/ClassLineMarkerProviderTest.kt

@@ -102,6 +102,28 @@ class ClassLineMarkerProviderTest : AbstractAxonFixtureTestCase() {
         )
     }
 
+    fun `test shows line marker on aggregate of hierarchy when recursive`() {
+        addFile(
+            "MyAggregate.kt", """
+            class RecursiveAggregateMember {
+                @AggregateMember
+                private var subItems: List<RecursiveAggregateMember>
+            }
+
+            @AggregateRoot
+            class MyAggregate {<caret>
+                @AggregateMember
+                private lateinit var singleMember: RecursiveAggregateMember
+            }
+        """.trimIndent(), open = true
+        )
+        Assertions.assertThat(hasLineMarker(ClassLineMarkerProvider::class.java)).isTrue
+        Assertions.assertThat(getLineMarkerOptions(ClassLineMarkerProvider::class.java)).containsExactly(
+            OptionSummary("MyAggregate", null, AxonIcons.Axon),
+            OptionSummary("- RecursiveAggregateMember", null, AxonIcons.Axon),
+        )
+    }
+
     fun `test shows line marker on child of hierarchy`() {
         addFile(
             "MyAggregate.kt", """