[AutoValue] NPE since v1.10 when using builder getters and nested builders

[jmesny]

Hi,

Since version 1.10 it is no longer possible to use builder getters and nested builders at the same time.

Here is an example describing the issue.

When the nested builder from Bar is exposed, the generated bar() builder getter in Foo does not work as expected.
The reason is that the generated implementation does not handle the case where the bar value would be missing, as stated by the Optional return type.
Calling this bar() method would lead to a NullPointerException being thrown.

The code below works with version 1.9.

import com.google.auto.value.AutoValue;

import java.util.Optional;

public class Issue {

    @AutoValue
    public static abstract class Foo {
        public abstract Bar bar();

        public static Foo.Builder builder() {
            return new AutoValue_Issue_Foo.Builder();
        }

        @AutoValue.Builder
        public abstract static class Builder {
            // https://github.com/google/auto/blob/master/value/userguide/builders-howto.md#normalize
            abstract Optional<Bar> bar();

            // Generated code for the above `bar()` method:

            // v1.9
            //    @Override
            //    Optional<Bar> bar() {
            //      if (bar == null) {
            //        return Optional.empty();
            //      } else {
            //        return Optional.of(bar);
            //      }
            //    }

            // v1.10
            //    @Override
            //    Optional<Bar> bar() {
            //      return Optional.of(bar);
            //    }

            public abstract Builder bar(Bar bar);

            // https://github.com/google/auto/blob/master/value/userguide/builders-howto.md#nested_builders
            public abstract Bar.Builder barBuilder();

            abstract Foo autoBuild();

            public Foo build() {
                if (bar().isEmpty()) {
                    // ^ NullPointerException when calling `bar()` with v1.10
                }
                return autoBuild();
            }
        }
    }

    @AutoValue
    public static abstract class Bar {
        public abstract Bar.Builder toBuilder();

        public static Bar.Builder builder() {
            return new AutoValue_Issue_Bar.Builder();
        }

        @AutoValue.Builder
        public abstract static class Builder {
            public abstract Bar build();
        }
    }


    public static void main(String[] args) {
        Foo.builder()
                .build();
    }
}

Thank you!

[eamonnmcmanus]

Thanks, we will investigate.