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Find inconsistent @Nullable override declarations

io.moderne.nullability.search.FindInconsistentOverrideNullability

Reports methods whose declared nullability is inconsistent with the method they override, a contract violation under NullAway. Because return types are covariant, an overriding method that declares a @Nullable return while the overridden supertype method returns a non-null value is flagged on its return. Because parameters are contravariant, an overriding method whose parameter is non-null while the overridden supertype method declares the corresponding parameter @Nullable is flagged on that parameter. Methods are matched across files by their erased signature name(paramTypes) plus a declaring-type subtype relationship. Conservative by design: legal covariant return narrowing and contravariant parameter widening are never flagged, and nothing is reported when a participating type cannot be resolved. Only Java sources are inspected; Kotlin and Groovy express nullability in the type system, which their compilers already enforce.

Recipe source​

This recipe is only available to users of Moderne.

This recipe is available under the Moderne Proprietary License.

Example​

Unchanged​
interface Service {
    String find();
}
Before​
import org.jspecify.annotations.Nullable;

class ServiceImpl implements Service {
    @Override
    public @Nullable String find() {
        return null;
    }
}
After​
import org.jspecify.annotations.Nullable;

class ServiceImpl implements Service {
    @Override
    public/*~~(@Nullable return is incompatible with non-null supertype return (NullAway override))~~>*/ @Nullable String find() {
        return null;
    }
}

Usage​

This recipe has no required configuration options. Users of Moderne can run it via the Moderne CLI.

You will need to have configured the Moderne CLI on your machine before you can run the following command.

shell
mod run . --recipe FindInconsistentOverrideNullability

If the recipe is not available locally, then you can install it using:

mod config recipes jar install io.moderne.recipe:rewrite-nullability:0.1.0

See how this recipe works across multiple open-source repositories​

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Please contact Moderne for more information about safely running the recipes on your own codebase in a private SaaS.

Data Tables​

Source files that had results​

org.openrewrite.table.SourcesFileResults

Source files that were modified by the recipe run.

Column NameDescription
Source path before the runThe source path of the file before the run. null when a source file was created during the run.
Source path after the runA recipe may modify the source path. This is the path after the run. null when a source file was deleted during the run.
Parent of the recipe that made changesIn a hierarchical recipe, the parent of the recipe that made a change. Empty if this is the root of a hierarchy or if the recipe is not hierarchical at all.
Recipe that made changesThe specific recipe that made a change.
Estimated time savingAn estimated effort that a developer to fix manually instead of using this recipe, in unit of seconds.
CycleThe recipe cycle in which the change was made.