0

Eclipse has null pointer annotation analysis and you can attach external annotations. http://www.lastnpe.org/ has documentation on that in case you stumble here and are confused.

Anyway if I attach the JDK external annotations (also known as *.eea files) and turn on the annotation analysis I can do the following (assume someObject is @Nullable):

Objects.requireNonNull(someObject);
someObject.toString() // No error/warning here as Eclipse apparently figured out that someObject isn't null.

The eea definition of requireNonNull is:

requireNonNull
 <T:Ljava/lang/Object;>(TT;)TT;
 <T:Ljava/lang/Object;>(T0T;)T1T;

Now if I make my own library lets call it MyObjects and attach the source and annotation (exactly like Objects.requireNonNull) I get a warning when I do the above:

MyObjects.likeRequireNonNull(someObject);
someObject.toString() // NP analysis warning/error here

Obviously I can get around it by re-assigning:

someObject = MyObjects.likeRequireNonNull(someObject);
someObject.toString(); // No error or warning.

but in some cases that isn't desirable (lambdas).

The above makes since because someObject is now being reassigned to a @NonNull.

What doesn't make since is how I can replicate the behavior of Objects.requireNonNull where I don't need to assign it back. I can't figure out how Eclipse knows via the external annotations that Objects.requireNonNull will guarantee the input variable not to be null in later usage.

EDIT: Apparently Objects.requireNonNull might be on a special whitelist according to this bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=553272

Adam Gent
  • 47,843
  • 23
  • 153
  • 203
  • 1
    Yes, there is an internal list of known methods as I mentioned [here](https://stackoverflow.com/a/51655802/2670892). MessageSend.detectAssertionUtility seems to be the method that does this check – greg-449 May 04 '21 at 07:04
  • Yes its a shame you can't customize it. It seems the EEA format could be extended such that more types could be added. Right now its 0 = Nullable and 1 = NonNull. What could be added is 4 more types: 2 for nullable/nonnull void like methods and 2 for nullable/nonnull for boolean like methods. – Adam Gent May 04 '21 at 12:58

0 Answers0