Why does the access of result annotated with `android.annotations.Nullable` generate a mere warning ...

# android

[arekolek]

Why does the access of result annotated with android.annotations.Nullable generate a mere warning instead of an error?

[Jay]

I’m new to android and Kotlin, but why isn’t it an optional? Is it to do with how it’s exposed from Java or something like that?

[gumil]

Because it is a platform call and the compiler reads it as a type String! which can be of type String or String?

[arekolek]

Yeah, so I’m asking, why is it a platform type

[arekolek]

Compare it with this:

[arekolek]

image.png

[arekolek]

Test is defined as:

import androidx.annotation.Nullable;

public class Test {

    @Nullable
    public String getAction() {
        throw new RuntimeException();
    }

}

[arekolek]

Why does the compiler understand the androidx.annotation.Nullable annotation but not the android.annotation.Nullable

[arekolek]

(the warning is coming from the linter, why can’t the compiler do that?)

[jw]

The android.jar doesn't use android.annotation.Nullable. It rewrites the bytecode to use android.annotation.RecentlyNullable which only triggers a warning. It will be an error in Q.

[arekolek]

Ah, ok thanks, now I see the announcement https://android-developers.googleblog.com/2018/08/android-pie-sdk-is-now-more-kotlin.html

Normally, nullability contract violations in Kotlin result in compilation errors. But to ensure the newly annotated APIs are compatible with your existing code, we are using an internal mechanism provided by the Kotlin compiler team to mark the APIs as recently annotated. […] The goal is to provide you with sufficient time to update your code.