Support @MonotonicNonNullDecl by default as an excluded field annotation

[chengniansun]

Do you plan to support @MonotonicNonNullDecl? Recently I added this annotation to guava (https://github.com/google/guava/blob/master/guava/src/com/google/common/reflect/TypeToken.java#L105)

Or more generally, do you support the nullness annotations of the checker framework?

[msridhar]

We can easily support interpreting the CF annotations as best as possible within the (less sophisticated) NullAway type system. Actually enhancing the power of the type system would be more work and would require some further justification in terms of additional reliability in practice, etc.

For this one, I think by default we would just treat the field as @NonNull. Are you looking for deeper support than that?

[msridhar]

Ah, I see. You're probably looking to not see reports of initialization errors on such fields, yes? If so, that can easily be handled using the -XepOpt:NullAway:ExcludedFieldAnnotations option (see here).

[chengniansun]

For this one, should we treat it in the following way,

If a field $f$ annotated with @monotonicnonnulldecl is not initialized in a constructor, NullAway does not emit a warning saying that " initializer method does not guarantee @nonnull fields f is initialized along all control-flow paths"

I am currently focusing on eliminating all warnings on uninitialized fields.

[msridhar]

Yeah, for now you can handle this by passing -XepOpt:NullAway:ExcludedFieldAnnotations=MonotonicNonNullDecl as an Error Prone / javac argument. For CF compatibility we should probably bake in support for this annotation.

[chengniansun]

Neat. Thank you.