spring - Springboot Mongo reactive repository unable to update nested list

Question

I wanted to update a nested list but I experience a strange behavior where I have to call method twice to get it done...

Here is my POJO:

@Document(collection = "company")
data class Company (
        val id: ObjectId,
        @Indexed(unique=true)
        val name: String,
        val customers: MutableList<Customer> = mutableListOf()
        //other fields
)

Below is my function from custom repository to do the job which I based on this tutorial

override fun addCustomer(customer: Customer): Mono<Company> {
    val query = Query(Criteria.where("employees.keycloakId").`is`(customer.createdBy))
    val update = Update().addToSet("customers", customer)
    val upsertOption = FindAndModifyOptions.options().upsert(true)
    //if I uncomment below this will work...
    //mongoTemplate.findAndModify(query, update, upsertOption, Company::class.java).block()
    return mongoTemplate.findAndModify(query, update, upsertOption, Company::class.java)
}

In order to actually add this customer I have to either uncomment the block call above or call the method two times in the debugger while running integration tests which is quite confusing to me

Here is the failing test

@Test
fun addCustomer() {
    //given
    val company = fixture.company
    val initialCustomerSize = company.customers.size

    companyRepository.save(company).block()

    val customerToAdd = CustomerReference(id = ObjectId.get(),
            keycloakId = "dummy",
            username = "customerName",
            email = "email",
            createdBy = company.employees[0].keycloakId)
    
    //when, then
    StepVerifier.create(companyCustomRepositoryImpl.addCustomer(customerToAdd))
            .assertNext { updatedCompany -> assertThat(updatedCompany.customers).hasSize(initialCustomerSize + 1) }
            .verifyComplete()

}

java.lang.AssertionError: Expected size:<3> but was:<2> in:

Answer 1

I found out the issue.

By default mongo returns entity with state of before update. To override it I had to add:

        val upsertOption = FindAndModifyOptions.options()
            .returnNew(true)
            .upsert(true)