Multiple @EnsuresNonNullIf should be ok; but the compiler complains

Question

The manual of the Checker Framework claims "You can write multiple @EnsuresNonNullIf annotations on a single method", however I observe the following message if I try this:

@EnsuresNonNullIf(expression="getFieldNames()", result=true)
@EnsuresNonNullIf(expression="getFieldName(i)", result=true)
public boolean hasFieldNames() {
    return fFieldNames != null;
}

The resulting error message by the Eclipse Java compiler:

Duplicate annotation of non-repeatable type @EnsuresNonNullIf. Only annotation types marked @Repeatable can be used multiple times at one target.

The resulting error message by the MVN javac compiler:

[ERROR] Blabla.java:[?,?] org.checkerframework.checker.nullness.qual.EnsuresNonNullIf is not a repeatable annotation type

I'm annotating 10-year-old code, so I'm hoping some configuration trick can safe the day :-) Without the multiple @EnsuresNonNullIf I'm up for quite a bit of manual code annotation to fix false positives that I'm not interested in...

PS: I tried using both checker-framework-2.8.1 and 2.9.0 with similar results, and always using <maven.compiler.source>1.8</maven.compiler.source>

score 0 · Accepted Answer · answered Jul 06 '19 at 08:11

I found this issue on the Checker Framework issue tracker: https://github.com/typetools/checker-framework/issues/1307

It explains an "enhancement" request for adding @Repeatable to the following CF annotations:

>  @DefaultQualifier -- DONE
>  @EnsuresKeyFor
>  @EnsuresKeyForIf
>  @EnsuresLockHeldIf
>  @EnsuresLTLengthOf
>  @EnsuresLTLengthOfIf
>  @EnsuresMinLenIf
>  @EnsuresNonNullIf
>  @EnsuresQualifier -- DONE
>  @EnsuresQualifierIf -- DONE
>  @FieldInvariant
>  @GuardSatisfied
>  @HasSubsequence
>  @MethodVal
>  @MinLenFieldInvariant
>  @RequiresQualifier -- DONE
>  @SubstringIndexFor

And the discussion contains a workaround, since EnsuresQualifiersIf is already repeatable:

@EnsuresQualifiersIf({
    @EnsuresQualifierIf(result=true, qualifier=NonNull.class, expression="getFoo()"),
    @EnsuresQualifierIf(result=false, qualifier=NonNull.class, expression="getBar()")
})
boolean hasFoo();

And in my case that works out to:

 @EnsuresQualifiersIf({
    @EnsuresQualifierIf(result=true, qualifier=NonNull.class, expression="getFieldNames()"),
    @EnsuresQualifierIf(result=true, qualifier=NonNull.class, expression="getFieldName(i)")
})
public boolean hasFieldNames() {
    return fFieldNames != null;
}

Multiple @EnsuresNonNullIf should be ok; but the compiler complains

1 Answers1