How to properly create index and avoid IndexNotReadyException

Hi community!

I am contributing to the Intellij plugin for the AEM platform (https://github.com/aemtools/aemtools).

I want to implement some completion functionality that should be based on configuration model described in Java.

The configuration model is a set of property keys and can be described in 2 variants (depends on AEM version):

- in class that is annotated with special annotation (@Component/@Service) the configuration model is a list of all fields (that are also annotated with special annotation @Property) values.

- in annotation class that is annotated with @ObjectClassDefinition the configuration model is a list of methods annotated with @AttributeDefinition annotation.

I tried to implement FileBasedIndex for JavaFileType.INSTANCE, but in Indexer implementation I faced the same issue like described in https://intellij-support.jetbrains.com/hc/en-us/community/posts/360008279279-Why-I-get-IndexNotReadyException-.

This is because I take annotations of PsiClass, get their qualifiedName and compare it with acceptable list of annotations. Please, see some pseudo-code below:

val javaPsiFile = inputData.psiFile as? PsiJavaFile ?: return mutableMapOf()

val mainFileClass = javaPsiFile.classes.toList()
val innerClasses = mainFileClass.flatMap { it.findChildrenByType(PsiClass::class.java) }
val allClasses = mainFileClass + innerClasses

val osgiConfigurationDeclarations: List<ConfigurationDeclarationModel> =
allClasses.filter {
    it.modifierList?.annotations?.toList().any { it.qualifiedName in listOf(ANNOTATION1, ANNOTATION2) }
}.map { ... }