I'm using firestore sdk for android which allows me to take a response and turn it into an object. My data class is defined as

data class Person(
    val name: String = "",
)

but if firestore sends

null

, then even though the type is non-null, if I put a breakpoint... I can see that I do actually get a null value? Question: How can a non-null property like

name

be null? I'm assuming this is because of reflection/java-interop or something?

I don't know anything about firestore/android, but if you think that java interop could be the issue here, than it's probably due to platform types. E.g. if you get a String from java code, it's Kotlin type will be

String!

. You can't create that type in Kotlin, only by java interop, and the thing is: the compiler will trust you, when you say it's not nullable! So

val platformStr: String! = someJavaFunction()
val nullableStr: String? = someKotlinFunction()

val s1: String = nullableStr // Compiler error! can't assign a nullable variable to a non-nullable one

val s2: String = platformStr // no Compiler error, but maybe still null!!! but the compiler trusts you to have more knowledge about the code then itself can deduce

So if you invoke java code and sometimes it returns

null

then set the type as nullable, so you're forced to handle the null-case. You can also check other articles on this topic, like this one https://p5v.medium.com/platform-types-in-kotlin-5caceeb556ad