Configuration

The following are a few notes on setting up NullAway on your own repo (mostly for Open Source).

The NullAway checker takes multiple configuration flags, in the format of http://errorprone.info/docs/flags . It will throw an error immediately upon loading if it does not receive at least one package for the required -XepOpt:NullAway:AnnotatedPackages flag, which tells it which code (and jars) to analyze.

The following flags are currently supported, each of them can take multiple values as a comma separated list:

• -XepOpt:NullAway:AnnotatedPackages=...

The list of packages that should be considered properly annotated according to the NullAway convention (every possibly null parameter / return / field annotated @Nullable).

• -XepOpt:NullAway:UnannotatedSubPackages=...

A list of subpackages to be excluded from the AnnotatedPackages list.

• -XepOpt:NullAway:KnownInitializers=...

The fully qualified name (without argument's, e.g. android.app.Activity.onCreate) of those methods from third-party libraries that NullAway should treat as initializers (equivalent to being annotated with an @Initializer annotation).

• -XepOpt:NullAway:ExcludedClassAnnotations=...

A list of annotations that cause classes to be excluded from nullability analysis.

• -XepOpt:NullAway:ExcludedFieldAnnotations=...

A list of annotations that cause fields to be excluded from being checked for proper initialization (e.g. javax.inject.Inject).

In addition to these options, NullAway will look for any classes implementing the com.uber.nullaway.LibraryModels interface, in the same classpath as the checker itself, and consider those as plug-in models for third-party unannotated libraries. Models defined in such classes will be loaded in addition to the default models for common Java and Android libraries included with the checker itself. For documentation on writing such custom models, refer to the javadoc documentation for com.uber.nullaway.LibraryModels itself.

The castToNonNull method does not ship with the NullAway Open-Source release, since its implementation is dependent on whichever logging infrastructure the analyzed code uses. Implementing your own version of this method is both recommended, and trivial:

@SuppressWarnings("CheckNullabilityTypes")
public static <T> T castToNonNull(@Nullable T x) {
    if (x == null) {
          // YOUR ERROR LOGGING AND REPORTING LOGIC GOES HERE
    }
    return x;
}